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/* This file is part of VoltDB.
* Copyright (C) 2008-2018 VoltDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with VoltDB. If not, see .
*/
package org.voltcore.zk;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.zookeeper_voltpatches.CreateMode;
import org.apache.zookeeper_voltpatches.KeeperException;
import org.apache.zookeeper_voltpatches.KeeperException.NoNodeException;
import org.apache.zookeeper_voltpatches.WatchedEvent;
import org.apache.zookeeper_voltpatches.Watcher;
import org.apache.zookeeper_voltpatches.ZooDefs.Ids;
import org.apache.zookeeper_voltpatches.ZooKeeper;
import org.apache.zookeeper_voltpatches.data.Stat;
import org.voltcore.logging.VoltLogger;
import org.voltcore.utils.CoreUtils;
import com.google_voltpatches.common.base.Throwables;
import com.google_voltpatches.common.collect.ImmutableSet;
import com.google_voltpatches.common.collect.Sets;
import com.google_voltpatches.common.util.concurrent.ListenableFuture;
import com.google_voltpatches.common.util.concurrent.ListeningExecutorService;
/*
* This state machine coexists with other SynchronizedStateManagers by using different branches of the
* ZooKeeper tree. This class provides a service to the StateMachineInstance class that reports changes
* to the membership. The ZooKeeper tree hierarchy is (quoted are reserved node names):
* |- rootNode
* |\
* | |- 'MEMBERS'
* | \
* | |- memberId
* \
* |- instanceName
* |\
* | |- 'LOCK_CONTENDERS'
* |\
* | |- 'BARRIER_PARTICIPANTS'
* \
* |- 'BARRIER_RESULTS'
*
* This hierarchy supports multiple topologies so one SynchronizedStatesManager could be used to track
* cluster membership while another could be used to track partition membership. Each SynchronizedStatesManager
* instance has a memberId that must be unique to the member community it is participating in. As the
* SynchronizedStatesManager is a shared service that can provide membership changes of other
* StateMachineInstances joining or leaving the community, all instances are considered tightly bound to the
* SynchronizedStatesManager. This means that the SynchronizedStatesManager will not join a community until
* all instances using that manager have registered with the SynchronizedStatesManager. Thus when a
* SynchronizedStatesManager informs its instances that a new member has joined the community (the set of
* nodes under the 'MEMBERS' node), the instance can be assured that it's peer instance is also there. This
* implies that StateMachineInstances can only coexist in the same SynchronizedStatesManager if all instances
* can be initialized (registered) before any individual instance needs to access the shared state.
*/
public class SynchronizedStatesManager {
private final AtomicBoolean m_done = new AtomicBoolean(false);
private final static String m_memberNode = "MEMBERS";
private Set m_groupMembers = new HashSet();
private final StateMachineInstance m_registeredStateMachines [];
private int m_registeredStateMachineInstances = 0;
private static final ListeningExecutorService m_shared_es = CoreUtils.getListeningExecutorService("SSM Daemon", 1);
// We assume that we are far enough along that the HostMessenger is up and running. Otherwise add to constructor.
private final ZooKeeper m_zk;
private final String m_ssmRootNode;
private final String m_stateMachineRoot;
private final String m_stateMachineMemberPath;
private String m_memberId;
private final String m_canonical_memberId;
private int m_resetCounter;
private int m_resetLimit;
private final int m_resetAllowance; // number of resets allowed within a reset clear threshold duration
private long m_lastResetTimeInMillis = -1L;
private static final long RESET_CLEAR_THRESHOLD = TimeUnit.DAYS.toMillis(1);
private enum REQUEST_TYPE {
INITIALIZING,
LAST_CHANGE_OUTCOME_REQUEST,
STATE_CHANGE_REQUEST,
CORRELATED_COORDINATED_TASK,
UNCORRELATED_COORDINATED_TASK
};
private enum RESULT_CONCENSUS {
AGREE,
DISAGREE,
NO_QUORUM
}
protected boolean addIfMissing(String absolutePath, CreateMode createMode, byte[] data)
throws KeeperException, InterruptedException {
return ZKUtil.addIfMissing(m_zk, absolutePath, createMode, data);
}
protected String getMemberId() {
return m_memberId;
}
/*
* Rules for each StateMachineInstance:
* 1. All access to the state machine is serialized by a per state machine local lock.
* 2. State changes may only be initiated by the oldest ephemeral lock node under the
* LOCK_CONTENDERS directory. This represents the distributed lock used to
* synchronize proposals by the members of the state machine.
* 3. When a new member joins an operational state machine, it must grab the lock node
* (2) before it can determine the current agreed state. However since it has to
* participate and benignly generate null results for all proposals, it can glean
* the state from the outcome of the next request it fully participates in. Note
* that an operation in progress during initialization of the new member is not
* used by the new member because the proposal initiator may have accepted the
* results and released the distributed lock before the new member can evaluate the
* results to determine the current state.
* 4. A member holding the distributed lock can propose a state change by clearing out
* the reported result nodes under the BARRIER_RESULTS node, updating the
* BARRIER_RESULTS node with the old and proposed state, and adding an ephemeral
* unique node under BARRIER_PARTICIPANTS to trigger the state machine members.
* Each proposal in the BARRIER_RESULTS node has a version number that is used
* by other members to distinguish a new proposal from a proposal it has already
* processed.
* 5. When a member detects a transition in the BARRIER_PARTICIPANTS node and a new
* version of the BARRIER_RESULTS node, it adds an ephemeral node for itself under
* BARRIER_PARTICIPANTS and copies the old and proposed state from the BARRIER_RESULTS
* node.
* 6. Each member evaluates the proposed state and inserts a SUCCESS or FAILURE indication
* in a persistent unique node under the BARRIER_RESULTS path.
* 7. A member may also request that an action be performed by all fully participating
* members (including itself) by assigning the existing state and a task proposal
* in the BARRIER_RESULTS node with a new version id and then adding a node under the
* BARRIER_PARTICIPANTS directory.
* 8. All members detecting the task request perform the task specified in the task
* proposal and inserting a result node under the BARRIER_RESULTS directory.
* 9. When the set of BARRIER_RESULTS nodes is a superset of all members currently in the
* state machine, all members are considered to have reported in and each member can
* independently determine the outcome. If the proposal was a state change request,
* and all BARRIER_RESULTS nodes report SUCCESS each member applies the new state
* and then removes itself from BARRIER_PARTICIPANTS. If the proposal was a task
* request, then members remove themselves from BARRIER_PARTICIPANTS to acknowledge
* receipt of all task results.
*10. Membership in the state machine can change as members join or fail. Membership is
* monitored by the SynchronizedStatesManager and changes are reported to each state
* machine instance. While members have joined but have not determined the current
* state, they report a NULL result for each state change or task proposal made by
* other members.
*11. If any member reports FAILURE node under the BARRIER_RESULTS directory after a
* state change request proposal, the new state is not applied by any member.
*12. Each member that has processed BARRIER_RESULTS removes its ephemeral node from the
* BARRIER_PARTICIPANTS directory node.
*13. The initiator of a state change or task releases the lock node when 9 is satisfied.
*14. A member is not told they have the lock node until the last member releases the
* lock node AND all ephemeral nodes under the BARRIER_PARTICIPANTS node are gone,
* indicating that all members waiting on the outcome of the last state change or
* task results have processed the previous outcome
*/
public abstract class StateMachineInstance {
protected String m_stateMachineId;
private final String m_stateMachineName;
private Set m_knownMembers;
private boolean m_membershipChangePending = false;
private final String m_statePath;
private final String m_lockPath;
private final String m_barrierResultsPath;
private String m_myResultPath;
private final String m_barrierParticipantsPath;
private String m_myParticipantPath;
private boolean m_stateChangeInitiator = false;
private String m_ourDistributedLockName = null;
private String m_lockWaitingOn = null;
private boolean m_holdingDistributedLock = false;
protected final VoltLogger m_log;
private ByteBuffer m_requestedInitialState = ByteBuffer.allocate(0);
private ByteBuffer m_synchronizedState = null;
private ByteBuffer m_pendingProposal = null;
private REQUEST_TYPE m_currentRequestType = REQUEST_TYPE.INITIALIZING;
private int m_currentParticipants = 0;
private Set m_memberResults = null;
private int m_lastProposalVersion = 0;
private boolean m_initializationCompleted = false;
private boolean isInitializationCompleted() {
lockLocalState();
unlockLocalState();
return m_initializationCompleted;
}
public int getResetCounter() {
return m_resetCounter;
}
private final Lock m_mutex = new ReentrantLock();
private int m_mutexLockedCnt = 0;
private final ThreadLocal m_mutexLocked = new ThreadLocal() {
@Override
protected Boolean initialValue()
{
return new Boolean(false);
}
};
private boolean debugVerifyLockAcquire() {
m_mutexLocked.set(new Boolean(true));
return m_mutexLockedCnt++ == 0;
}
private boolean debugVerifyLockRelease() {
m_mutexLocked.set(new Boolean(false));
return (m_mutexLockedCnt-- == 1);
}
protected boolean debugIsLocalStateLocked() {
return m_mutexLocked.get();
}
private void lockLocalState() {
m_mutex.lock();
assert(debugVerifyLockAcquire());
}
// This wrapper resolves getStackTrace correctly when debugging locking
private void lockLocalStateForLockRunner() {
lockLocalState();
}
// This wrapper resolves getStackTrace correctly when debugging locking
private void lockLocalStateForResultsRunner() {
lockLocalState();
}
// This wrapper resolves getStackTrace correctly when debugging locking
private void lockLocalStateForParticipantRunner() {
lockLocalState();
}
private void unlockLocalState() {
assert(debugVerifyLockRelease());
m_mutex.unlock();
}
private class LockWatcher implements Watcher {
@Override
public void process(final WatchedEvent event) {
try {
if (!m_done.get()) {
m_shared_es.submit(HandlerForDistributedLockEvent);
}
} catch (RejectedExecutionException e) {
}
}
}
private final LockWatcher m_lockWatcher = new LockWatcher();
private class BarrierParticipantsWatcher implements Watcher {
@Override
public void process(final WatchedEvent event) {
try {
if (!m_done.get()) {
m_shared_es.submit(HandlerForBarrierParticipantsEvent);
}
} catch (RejectedExecutionException e) {
}
}
}
class StateChangeRequest {
public final REQUEST_TYPE m_requestType;
public final ByteBuffer m_previousState;
public final ByteBuffer m_proposal;
private StateChangeRequest(REQUEST_TYPE requestType, ByteBuffer previousState, ByteBuffer proposedState) {
m_requestType = requestType;
m_previousState = previousState;
m_proposal = proposedState;
}
}
private final BarrierParticipantsWatcher m_barrierParticipantsWatcher = new BarrierParticipantsWatcher();
private class BarrierResultsWatcher implements Watcher {
@Override
public void process(final WatchedEvent event) {
try {
if (!m_done.get()) {
m_shared_es.submit(HandlerForBarrierResultsEvent);
}
} catch (RejectedExecutionException e) {
}
}
};
private final BarrierResultsWatcher m_barrierResultsWatcher = new BarrierResultsWatcher();
// Used only for Mocking StateMachineInstance
public StateMachineInstance()
{
m_statePath = "MockInstanceStatePath";
m_barrierResultsPath = "MockBarrierResultsPath";
m_myResultPath = "MockMyResultPath";
m_barrierParticipantsPath = "MockParticipantsPath";
m_myParticipantPath = "MockMyParticipantPath";
m_lockPath = "MockLockPath";
m_log = null;
m_stateMachineId = "MockStateMachineId";
m_stateMachineName = "MockStateMachineName";
}
public StateMachineInstance(String instanceName, VoltLogger logger) throws RuntimeException {
if (instanceName.equals(m_memberNode)) {
throw new RuntimeException("State machine name may not be named " + m_memberNode);
}
assert(!instanceName.equals(m_memberNode));
m_stateMachineName = instanceName;
m_statePath = ZKUtil.joinZKPath(m_stateMachineRoot, instanceName);
m_lockPath = ZKUtil.joinZKPath(m_statePath, "LOCK_CONTENDERS");
m_barrierResultsPath = ZKUtil.joinZKPath(m_statePath, "BARRIER_RESULTS");
m_myResultPath = ZKUtil.joinZKPath(m_barrierResultsPath, m_memberId);
m_barrierParticipantsPath = ZKUtil.joinZKPath(m_statePath, "BARRIER_PARTICIPANTS");
m_myParticipantPath = ZKUtil.joinZKPath(m_barrierParticipantsPath, m_memberId);
m_log = logger;
m_stateMachineId = "SMI " + m_ssmRootNode + "/" + m_stateMachineName + "/" + m_memberId;
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + " created.");
}
}
public void registerStateMachineWithManager(ByteBuffer requestedInitialState) throws InterruptedException {
assert(requestedInitialState != null);
assert(requestedInitialState.remaining() < Short.MAX_VALUE);
m_requestedInitialState = requestedInitialState;
registerStateMachine(this);
}
/**
* Notify the derived class that the state machine instance is being reset,
* the derived class should reset its own specific states and provide a reset state
* @param isDirectVictim true if the reset is caused by callback exception in this instance
* @return a ByteBuffer encapsulating the reset state provided by the derived class
*/
protected abstract ByteBuffer notifyOfStateMachineReset(boolean isDirectVictim);
private void initializeStateMachine(Set knownMembers) throws KeeperException, InterruptedException {
addIfMissing(m_statePath, CreateMode.PERSISTENT, null);
addIfMissing(m_lockPath, CreateMode.PERSISTENT, null);
addIfMissing(m_barrierParticipantsPath, CreateMode.PERSISTENT, null);
lockLocalState();
boolean ownDistributedLock = requestDistributedLock();
ByteBuffer startStates = buildProposal(REQUEST_TYPE.INITIALIZING,
m_requestedInitialState.asReadOnlyBuffer(), m_requestedInitialState.asReadOnlyBuffer());
addIfMissing(m_barrierResultsPath, CreateMode.PERSISTENT, startStates.array());
boolean stateMachineNodeCreated = false;
if (ownDistributedLock) {
// Only the very first initializer of the state machine will both get the lock and successfully
// allocate "STATE_INITIALIZED". This guarantees that only one node will assign the initial state.
stateMachineNodeCreated = addIfMissing(ZKUtil.joinZKPath(m_statePath, "STATE_INITIALIZED"),
CreateMode.PERSISTENT, null);
}
if (m_membershipChangePending) {
getLatestMembership();
}
else {
m_knownMembers = knownMembers;
}
// We need to always monitor participants so that if we are initialized we can add ourselves and insert
// our results and if we are not initialized, we can always auto-insert a null result.
if (stateMachineNodeCreated) {
assert(ownDistributedLock);
m_synchronizedState = m_requestedInitialState;
m_requestedInitialState = null;
m_lastProposalVersion = getProposalVersion();
ByteBuffer readOnlyResult = m_synchronizedState.asReadOnlyBuffer();
// Add an acceptable result so the next initializing member recognizes an immediate quorum.
byte result[] = new byte[1];
result[0] = (byte)(1);
addResultEntry(result);
m_lockWaitingOn = "bogus"; // Avoids call to notifyDistributedLockWaiter
m_log.info(m_stateMachineId + ": Initialized (first member) with State " +
stateToString(m_synchronizedState.asReadOnlyBuffer()));
m_initializationCompleted = true;
cancelDistributedLock();
checkForBarrierParticipantsChange();
// Notify the derived object that we have a stable state
try {
setInitialState(readOnlyResult);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
else {
// To get a stable result set, we need to get the lock for this state machine. If someone else has the
// lock they can clear the stale results out from under us.
if (ownDistributedLock) {
initializeFromActiveCommunity();
}
else {
// This means we will ignore the current update if there is one in progress.
// Note that if we are not the next waiter for the lock, we will blindly
// accept the next proposal and use the outcome to set our initial state.
addResultEntry(null);
Stat nodeStat = new Stat();
boolean resultNodeFound = false;
{
try {
m_zk.getData(m_barrierResultsPath, false, nodeStat);
resultNodeFound = true;
}
catch (NoNodeException noNode) {
// This is a race between another node who got the Distributed lock but
// Has not set up the result path yet. Keep Retrying.
}
} while (!resultNodeFound);
m_lastProposalVersion = nodeStat.getVersion();
checkForBarrierParticipantsChange();
}
assert(!debugIsLocalStateLocked());
}
}
/*
* This state machine and all other state machines under this manager are being removed
*/
private void disableMembership() throws InterruptedException {
lockLocalState();
// put in two separate try-catch blocks so that both actions are attempted
try {
m_zk.delete(m_myParticipantPath, -1);
}
catch (KeeperException e) {
}
try {
if (m_ourDistributedLockName != null) {
m_zk.delete(m_ourDistributedLockName, -1);
}
}
catch (KeeperException e) {
}
m_initializationCompleted = false;
unlockLocalState();
}
private void reset(boolean isDirectVictim) {
ByteBuffer resetState = notifyOfStateMachineReset(isDirectVictim);
// if we are the direct victim, use the reset state as requested initial state
if (isDirectVictim) {
m_requestedInitialState = resetState;
}
// else simply use currently requested initial state or synchronized state as requested initial state
else {
if (m_requestedInitialState == null) {
assert(m_synchronizedState != null);
m_requestedInitialState = m_synchronizedState;
}
}
m_synchronizedState = null;
m_membershipChangePending = false;
m_stateChangeInitiator = false;
m_ourDistributedLockName = null;
m_lockWaitingOn = null;
m_holdingDistributedLock = false;
m_pendingProposal = null;
m_currentRequestType = REQUEST_TYPE.INITIALIZING;
m_memberResults = null;
m_lastProposalVersion = 0;
m_mutexLockedCnt = 0;
m_myResultPath = ZKUtil.joinZKPath(m_barrierResultsPath, m_memberId);
m_myParticipantPath = ZKUtil.joinZKPath(m_barrierParticipantsPath, m_memberId);
m_stateMachineId = "SMI " + m_ssmRootNode + "/" + m_stateMachineName + "/" + m_memberId;
}
private int getProposalVersion() {
int proposalVersion = -1;
try {
Stat nodeStat = new Stat();
m_zk.getData(m_barrierResultsPath, null, nodeStat);
proposalVersion = nodeStat.getVersion();
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in getProposalVersion");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in getProposalVersion");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in getProposalVersion");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
return proposalVersion;
}
private ByteBuffer buildProposal(REQUEST_TYPE requestType, ByteBuffer existingState, ByteBuffer proposedState) {
ByteBuffer states = ByteBuffer.allocate(proposedState.remaining() + existingState.remaining() + 4);
states.putShort((short)requestType.ordinal());
states.putShort((short)existingState.remaining());
states.put(existingState);
states.put(proposedState);
states.flip();
return states;
}
private StateChangeRequest getExistingAndProposedBuffersFromResultsNode(byte oldAndNewState[]) {
// Either the barrier or the state node should have the current state
assert(oldAndNewState != null);
ByteBuffer states = ByteBuffer.wrap(oldAndNewState);
// Maximum state size is 64K
REQUEST_TYPE requestType = REQUEST_TYPE.values()[states.getShort()];
int oldStateSize = states.getShort();
states.position(oldStateSize+4);
ByteBuffer proposedState = states.slice();
states.flip(); // just the old state
states.position(4);
states.limit(oldStateSize+4);
return new StateChangeRequest(requestType, states, proposedState);
}
private void checkForBarrierParticipantsChange() {
assert(debugIsLocalStateLocked());
try {
Set children = ImmutableSet.copyOf(m_zk.getChildren(m_barrierParticipantsPath, m_barrierParticipantsWatcher));
Stat nodeStat = new Stat();
// inspect the m_barrierResultsPath and get the new and old states and version
// At some point this can be optimized to not examine the proposal all the time
byte statePair[] = m_zk.getData(m_barrierResultsPath, false, nodeStat);
int proposalVersion = nodeStat.getVersion();
if (proposalVersion != m_lastProposalVersion) {
m_lastProposalVersion = proposalVersion;
m_currentParticipants = children.size();
if (!m_stateChangeInitiator) {
assert(m_pendingProposal == null);
// This is an indication that a new state change is being requested
StateChangeRequest existingAndProposedStates = getExistingAndProposedBuffersFromResultsNode(statePair);
m_currentRequestType = existingAndProposedStates.m_requestType;
if (m_requestedInitialState != null) {
// Since we have not initialized yet, we acknowledge this proposal with an empty result.
addResultEntry(null);
unlockLocalState();
}
else {
// Don't add ourselves as a participant because we don't care about the results
REQUEST_TYPE type = m_currentRequestType;
if (type == REQUEST_TYPE.LAST_CHANGE_OUTCOME_REQUEST) {
// The request is from a new member who found the results in an ambiguous state.
byte result[] = new byte[1];
if (existingAndProposedStates.m_proposal.equals(m_synchronizedState)) {
result[0] = (byte)1;
addResultEntry(result);
}
else {
assert(existingAndProposedStates.m_previousState.equals(m_synchronizedState));
result[0] = (byte)0;
addResultEntry(result);
}
unlockLocalState();
}
else {
// We track the number of people waiting on the results so we know when the result is stale and
// the next lock holder can initiate a new state proposal.
m_zk.create(m_myParticipantPath, null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
m_pendingProposal = existingAndProposedStates.m_proposal;
ByteBuffer proposedState = m_pendingProposal.asReadOnlyBuffer();
assert(existingAndProposedStates.m_previousState.equals(m_synchronizedState));
if (m_log.isDebugEnabled()) {
if (type == REQUEST_TYPE.STATE_CHANGE_REQUEST) {
m_log.debug(m_stateMachineId + ": Received new State proposal " +
stateToString(proposedState.asReadOnlyBuffer()));
}
else {
m_log.debug(m_stateMachineId + ": Received new Task request " +
taskToString(proposedState.asReadOnlyBuffer()));
}
}
unlockLocalState();
if (type == REQUEST_TYPE.STATE_CHANGE_REQUEST) {
try {
stateChangeProposed(proposedState);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
else {
try {
taskRequested(proposedState);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
}
}
}
else {
// We initiated a proposal and if it is a TASK we need to call our derived object to kick it off
assert(m_pendingProposal != null);
if (m_currentRequestType == REQUEST_TYPE.CORRELATED_COORDINATED_TASK ||
m_currentRequestType == REQUEST_TYPE.UNCORRELATED_COORDINATED_TASK) {
// This is a Task request made by us so notify the derived state machine to perform the task
// provide a result.
ByteBuffer taskRequest = m_pendingProposal.asReadOnlyBuffer();
unlockLocalState();
try {
taskRequested(taskRequest);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
else {
unlockLocalState();
}
}
}
else {
m_currentParticipants = children.size();
if (m_ourDistributedLockName != null && m_ourDistributedLockName == m_lockWaitingOn && children.size() == 0) {
// We can finally notify the lock waiter because everyone is finished evaluating the previous state proposal
notifyDistributedLockWaiter();
}
else {
unlockLocalState();
}
}
} catch (KeeperException.SessionExpiredException e) {
// lost the full connection. some test cases do this...
// means zk shutdown without the elector being shutdown.
// ignore.
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in checkForBarrierParticipantsChange");
}
unlockLocalState();
} catch (KeeperException.ConnectionLossException e) {
// lost the full connection. some test cases do this...
// means shutdown without the elector being
// shutdown; ignore.
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in checkForBarrierParticipantsChange");
}
unlockLocalState();
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in checkForBarrierParticipantsChange");
}
unlockLocalState();
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
assert(!debugIsLocalStateLocked());
}
private void monitorParticipantChanges() {
// always start checking for participation changes after the result notifications
// or initialization notifications to ensure these notifications happen before lock
// ownership notifications.
lockLocalState();
checkForBarrierParticipantsChange();
}
private RESULT_CONCENSUS resultsAgreeOnSuccess(Set memberList) throws Exception {
boolean agree = false;
for (String memberId : memberList) {
byte result[];
try {
result = m_zk.getData(ZKUtil.joinZKPath(m_barrierResultsPath, memberId), false, null);
if (result != null) {
if (result[0] == 0) {
return RESULT_CONCENSUS.DISAGREE;
}
agree = true;
}
}
catch (NoNodeException ke) {
// This can happen when a new member joins and other members detect the new member before
// it's initialization code is called and a Null result is supplied to treat this as a null result.
}
}
if (agree) {
return RESULT_CONCENSUS.AGREE;
}
return RESULT_CONCENSUS.NO_QUORUM;
}
private ArrayList getUncorrelatedResults(ByteBuffer taskRequest, Set memberList) {
// Treat ZooKeeper failures as empty result
ArrayList results = new ArrayList();
try {
for (String memberId : memberList) {
byte result[];
result = m_zk.getData(ZKUtil.joinZKPath(m_barrierResultsPath, memberId), false, null);
if (result != null) {
ByteBuffer bb = ByteBuffer.wrap(result);
results.add(bb);
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": " + memberId + " reports Result " +
taskResultToString(taskRequest.asReadOnlyBuffer(), bb.asReadOnlyBuffer()));
}
}
else {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": " + memberId + " did not supply a Task Result");
}
}
}
// Remove ourselves from the participants list to unblock the next distributed lock waiter
m_zk.delete(m_myParticipantPath, -1);
} catch (KeeperException.SessionExpiredException e) {
results = new ArrayList();
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in getUncorrelatedResults");
}
} catch (KeeperException.ConnectionLossException e) {
results = new ArrayList();
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in getUncorrelatedResults");
}
} catch (InterruptedException e) {
results = new ArrayList();
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in getUncorrelatedResults");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
return results;
}
private Map getCorrelatedResults(ByteBuffer taskRequest, Set memberList) {
// Treat ZooKeeper failures as empty result
Map results = new HashMap();
try {
for (String memberId : memberList) {
byte result[];
result = m_zk.getData(ZKUtil.joinZKPath(m_barrierResultsPath, memberId), false, null);
if (result != null) {
ByteBuffer bb = ByteBuffer.wrap(result);
results.put(memberId, bb);
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": " + memberId + " reports Result " +
taskResultToString(taskRequest.asReadOnlyBuffer(), bb.asReadOnlyBuffer()));
}
}
else {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": " + memberId + " did not supply a Task Result");
}
}
}
// Remove ourselves from the participants list to unblock the next distributed lock waiter
m_zk.delete(m_myParticipantPath, -1);
} catch (KeeperException.SessionExpiredException e) {
results = new HashMap();
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in getCorrelatedResults");
}
} catch (KeeperException.ConnectionLossException e) {
results = new HashMap();
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in getCorrelatedResults");
}
} catch (InterruptedException e) {
results = new HashMap();
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in getCorrelatedResults");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
return results;
}
// The number of results is a superset of the membership so analyze the results
private void processResultQuorum(Set memberList) {
assert(m_currentRequestType != REQUEST_TYPE.INITIALIZING);
m_memberResults = null;
if (m_requestedInitialState != null) {
// We can now initialize this state machine instance
assert(m_holdingDistributedLock);
try {
assert(m_synchronizedState == null);
Stat versionInfo = new Stat();
byte oldAndProposedState[] = m_zk.getData(m_barrierResultsPath, false, versionInfo);
assert(versionInfo.getVersion() == m_lastProposalVersion);
StateChangeRequest existingAndProposedStates =
getExistingAndProposedBuffersFromResultsNode(oldAndProposedState);
m_currentRequestType = existingAndProposedStates.m_requestType;
// We are waiting to initialize. We are here either because we are piggy-backing
// another member's proposal or because we initiated a LAST_CHANGE_OUTCOME_REQUEST
if (m_currentRequestType == REQUEST_TYPE.LAST_CHANGE_OUTCOME_REQUEST) {
// We don't have a result yet but it is available
RESULT_CONCENSUS result = resultsAgreeOnSuccess(memberList);
if (result == RESULT_CONCENSUS.NO_QUORUM) {
// Bad news. There is no definitive state so if we are the distributed
// lock owner we will assign our initial state as our initial state
if (m_stateChangeInitiator) {
m_synchronizedState = m_requestedInitialState;
ByteBuffer stableState = buildProposal(REQUEST_TYPE.INITIALIZING,
m_synchronizedState.asReadOnlyBuffer(), m_synchronizedState.asReadOnlyBuffer());
Stat newProposalStat = m_zk.setData(m_barrierResultsPath, stableState.array(), -1);
m_lastProposalVersion = newProposalStat.getVersion();
}
}
else {
// There was at least one member that knows the definitive state
if (result == RESULT_CONCENSUS.AGREE) {
m_synchronizedState = existingAndProposedStates.m_proposal;
}
else {
m_synchronizedState = existingAndProposedStates.m_previousState;
}
}
}
else
if (m_currentRequestType == REQUEST_TYPE.STATE_CHANGE_REQUEST) {
// We don't have a result yet but it is available
RESULT_CONCENSUS result = resultsAgreeOnSuccess(memberList);
if (result == RESULT_CONCENSUS.AGREE) {
m_synchronizedState = existingAndProposedStates.m_proposal;
}
else {
assert(result == RESULT_CONCENSUS.DISAGREE);
m_synchronizedState = existingAndProposedStates.m_previousState;
}
}
else {
// If we are processing a TASK or a updated STABLE result, we don't need a quorum
m_synchronizedState = existingAndProposedStates.m_previousState;
}
// Remove ourselves from the participants list to unblock the next distributed lock waiter
m_zk.delete(m_myParticipantPath, -1);
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in processResultQuorum");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in processResultQuorum");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in processResultQuorum");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
if (m_stateChangeInitiator) {
m_stateChangeInitiator = false;
cancelDistributedLock();
}
if (m_synchronizedState != null) {
ByteBuffer readOnlyResult = m_synchronizedState.asReadOnlyBuffer();
// We were not yet participating in the state machine so but now we can
m_requestedInitialState = null;
m_pendingProposal = null;
m_log.info(m_stateMachineId + ": Initialized (concensus) with State " +
stateToString(m_synchronizedState.asReadOnlyBuffer()));
m_initializationCompleted = true;
unlockLocalState();
try {
setInitialState(readOnlyResult);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
if (m_initializationCompleted) {
// If we are ready to provide an initial state to the derived state machine, add us to
// participants watcher so we can see the next request
monitorParticipantChanges();
}
}
else {
unlockLocalState();
}
}
else {
assert(m_currentRequestType != REQUEST_TYPE.LAST_CHANGE_OUTCOME_REQUEST);
boolean initiator = m_stateChangeInitiator;
boolean success = false;
if (m_currentRequestType == REQUEST_TYPE.STATE_CHANGE_REQUEST) {
// Treat ZooKeeper failures as unsuccessful proposal
ByteBuffer attemptedChange = m_pendingProposal.asReadOnlyBuffer();
try {
// We don't have a result yet but it is available
RESULT_CONCENSUS result = resultsAgreeOnSuccess(memberList);
// Now that we have a result we can remove ourselves from the participants list.
m_zk.delete(m_myParticipantPath, -1);
if (result == RESULT_CONCENSUS.AGREE) {
success = true;
m_synchronizedState = m_pendingProposal;
}
else {
assert(result == RESULT_CONCENSUS.DISAGREE);
}
m_pendingProposal = null;
if (m_stateChangeInitiator) {
// Since we don't care if we are the last to go away, remove ourselves from the participant list
assert(m_holdingDistributedLock);
m_stateChangeInitiator = false;
cancelDistributedLock();
}
} catch (KeeperException.SessionExpiredException e) {
success = false;
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in processResultQuorum");
}
} catch (KeeperException.ConnectionLossException e) {
success = false;
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in processResultQuorum");
}
} catch (InterruptedException e) {
success = false;
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in processResultQuorum");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
success = false;
}
m_log.info(m_stateMachineId + ": Proposed state " + (success?"succeeded ":"failed ") +
stateToString(attemptedChange.asReadOnlyBuffer()));
unlockLocalState();
// Notify the derived state machine engine of the current state
try {
proposedStateResolved(initiator, attemptedChange, success);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
if (m_initializationCompleted) {
monitorParticipantChanges();
}
}
else {
// Process the results of a TASK request
ByteBuffer taskRequest = m_pendingProposal.asReadOnlyBuffer();
m_pendingProposal = null;
m_log.info(m_stateMachineId + ": All members completed task " + taskToString(taskRequest.asReadOnlyBuffer()));
if (m_currentRequestType == REQUEST_TYPE.CORRELATED_COORDINATED_TASK) {
Map results = getCorrelatedResults(taskRequest, memberList);
if (m_stateChangeInitiator) {
// Since we don't care if we are the last to go away, remove ourselves from the participant list
assert(m_holdingDistributedLock);
m_stateChangeInitiator = false;
cancelDistributedLock();
}
unlockLocalState();
try {
correlatedTaskCompleted(initiator, taskRequest, results);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
else {
ArrayList results = getUncorrelatedResults(taskRequest, memberList);
if (m_stateChangeInitiator) {
// Since we don't care if we are the last to go away, remove ourselves from the participant list
assert(m_holdingDistributedLock);
m_stateChangeInitiator = false;
cancelDistributedLock();
}
unlockLocalState();
try {
uncorrelatedTaskCompleted(initiator, taskRequest, results);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
if (m_initializationCompleted) {
monitorParticipantChanges();
}
}
}
}
private void checkForBarrierResultsChanges() {
assert(debugIsLocalStateLocked());
if (m_pendingProposal == null) {
// Don't check for barrier results until we notice the participant list change.
unlockLocalState();
return;
}
Set membersWithResults;
try {
membersWithResults = ImmutableSet.copyOf(m_zk.getChildren(m_barrierResultsPath,
m_barrierResultsWatcher));
} catch (KeeperException.SessionExpiredException e) {
membersWithResults = new TreeSet(Arrays.asList("We died so avoid Quorum path"));
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in checkForBarrierResultsChanges");
}
} catch (KeeperException.ConnectionLossException e) {
membersWithResults = new TreeSet(Arrays.asList("We died so avoid Quorum path"));
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in checkForBarrierResultsChanges");
}
} catch (InterruptedException e) {
membersWithResults = new TreeSet(Arrays.asList("We died so avoid Quorum path"));
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in checkForBarrierResultsChanges");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
membersWithResults = new TreeSet();
}
if (Sets.difference(m_knownMembers, membersWithResults).isEmpty()) {
processResultQuorum(membersWithResults);
assert(!debugIsLocalStateLocked());
}
else {
m_memberResults = membersWithResults;
unlockLocalState();
}
}
/*
* Assumes this state machine owns the distributed lock and can either interrogate the existing state
* or request the current state from the community (if the existing state is ambiguous)
*/
private void initializeFromActiveCommunity() {
ByteBuffer readOnlyResult = null;
ByteBuffer staleTask = null;
byte oldAndProposedState[];
try {
Stat lastProposal = new Stat();
oldAndProposedState = m_zk.getData(m_barrierResultsPath, false, lastProposal);
StateChangeRequest existingAndProposedStates =
getExistingAndProposedBuffersFromResultsNode(oldAndProposedState);
if (existingAndProposedStates.m_requestType == REQUEST_TYPE.LAST_CHANGE_OUTCOME_REQUEST) {
RESULT_CONCENSUS result = resultsAgreeOnSuccess(m_knownMembers);
if (result == RESULT_CONCENSUS.AGREE) {
// Fall through to set up the initial state and provide notification of initialization
existingAndProposedStates = new StateChangeRequest(REQUEST_TYPE.INITIALIZING,
existingAndProposedStates.m_proposal.asReadOnlyBuffer(),
existingAndProposedStates.m_proposal.asReadOnlyBuffer());
}
else
if (result == RESULT_CONCENSUS.DISAGREE) {
// Fall through to set up the initial state and provide notification of initialization
existingAndProposedStates = new StateChangeRequest(REQUEST_TYPE.INITIALIZING,
existingAndProposedStates.m_previousState.asReadOnlyBuffer(),
existingAndProposedStates.m_previousState.asReadOnlyBuffer());
}
else {
// Another members outcome request was completed but a subsequent proposing member died
// between the time the results of this last request were removed and the new proposal
// was made. Fall through and propose a new LAST_CHANGE_OUTCOME_REQUEST.
existingAndProposedStates = new StateChangeRequest(REQUEST_TYPE.STATE_CHANGE_REQUEST,
existingAndProposedStates.m_previousState.asReadOnlyBuffer(),
existingAndProposedStates.m_proposal.asReadOnlyBuffer());
}
}
if (existingAndProposedStates.m_requestType == REQUEST_TYPE.STATE_CHANGE_REQUEST) {
// The last lock owner died before completing a state change or determining the current state
m_stateChangeInitiator = true;
m_pendingProposal = m_requestedInitialState;
m_currentRequestType = REQUEST_TYPE.LAST_CHANGE_OUTCOME_REQUEST;
ByteBuffer stateChange = buildProposal(REQUEST_TYPE.LAST_CHANGE_OUTCOME_REQUEST,
existingAndProposedStates.m_previousState, existingAndProposedStates.m_proposal);
m_lastProposalVersion = wakeCommunityWithProposal(stateChange.array());
addResultEntry(null);
checkForBarrierResultsChanges();
}
else {
assert(existingAndProposedStates.m_requestType == REQUEST_TYPE.INITIALIZING ||
existingAndProposedStates.m_requestType == REQUEST_TYPE.CORRELATED_COORDINATED_TASK ||
existingAndProposedStates.m_requestType == REQUEST_TYPE.UNCORRELATED_COORDINATED_TASK);
m_synchronizedState = existingAndProposedStates.m_previousState;
m_requestedInitialState = null;
readOnlyResult = m_synchronizedState.asReadOnlyBuffer();
m_lastProposalVersion = lastProposal.getVersion();
m_pendingProposal = null;
m_log.info(m_stateMachineId + ": Initialized (existing) with State " +
stateToString(m_synchronizedState.asReadOnlyBuffer()));
if (existingAndProposedStates.m_requestType != REQUEST_TYPE.INITIALIZING) {
staleTask = existingAndProposedStates.m_proposal.asReadOnlyBuffer();
}
m_initializationCompleted = true;
cancelDistributedLock();
// Add an acceptable result so the next initializing member recognizes an immediate quorum.
m_lockWaitingOn = "bogus"; // Avoids call to notifyDistributedLockWaiter below
checkForBarrierParticipantsChange();
}
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in initializeFromActiveCommunity");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in initializeFromActiveCommunity");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in initializeFromActiveCommunity");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
if (readOnlyResult != null) {
// Notify the derived object that we have a stable state
try {
setInitialState(readOnlyResult);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
if (staleTask != null) {
try {
staleTaskRequestNotification(staleTask);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
}
private int wakeCommunityWithProposal(byte[] proposal) {
assert(m_holdingDistributedLock);
assert(m_currentParticipants == 0);
int newProposalVersion = -1;
try {
List results = m_zk.getChildren(m_barrierResultsPath, false);
for (String resultNode : results) {
m_zk.delete(ZKUtil.joinZKPath(m_barrierResultsPath, resultNode), -1);
}
Stat newProposalStat = m_zk.setData(m_barrierResultsPath, proposal, -1);
m_zk.create(m_myParticipantPath, null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
newProposalVersion = newProposalStat.getVersion();
// force the participant count to be 1, so that lock notifications can be correctly guarded
m_currentParticipants = 1;
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in wakeCommunityWithProposal");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in wakeCommunityWithProposal");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in wakeCommunityWithProposal");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
return newProposalVersion;
}
private final Runnable HandlerForBarrierParticipantsEvent = new Runnable() {
@Override
public void run() {
lockLocalStateForParticipantRunner();
checkForBarrierParticipantsChange();
assert(!debugIsLocalStateLocked());
}
};
private final Runnable HandlerForBarrierResultsEvent = new Runnable() {
@Override
public void run() {
lockLocalStateForResultsRunner();
checkForBarrierResultsChanges();
assert(!debugIsLocalStateLocked());
}
};
private String getNextLockNodeFromList() throws Exception {
List lockRequestors = m_zk.getChildren(m_lockPath, false);
Collections.sort(lockRequestors);
ListIterator iter = lockRequestors.listIterator();
String currRequestor = null;
while (iter.hasNext()) {
currRequestor = ZKUtil.joinZKPath(m_lockPath, iter.next());
if (currRequestor.equals(m_ourDistributedLockName)) {
break;
}
}
assert (currRequestor != null); // We should be able to find ourselves
//Back on currRequestor
iter.previous();
String nextLower = null;
//Until we have previous nodes and we set a watch on previous node.
while (iter.hasPrevious()) {
//Process my lower nodes and put a watch on whats live
String previous = ZKUtil.joinZKPath(m_lockPath, iter.previous());
if (m_zk.exists(previous, m_lockWatcher) != null) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": " + m_ourDistributedLockName + " waiting on " + previous);
}
nextLower = previous;
break;
}
}
//If we could not watch any lower node we are lowest and must own the lock.
if (nextLower == null) {
return m_ourDistributedLockName;
}
return nextLower;
}
private final Runnable HandlerForDistributedLockEvent = new Runnable() {
@Override
public void run() {
lockLocalStateForLockRunner();
if (m_ourDistributedLockName != null) {
try {
m_lockWaitingOn = getNextLockNodeFromList();
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in HandlerForDistributedLockEvent");
}
m_lockWaitingOn = "We died so we can't ever get the distributed lock";
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in HandlerForDistributedLockEvent");
}
m_lockWaitingOn = "We died so we can't ever get the distributed lock";
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in HandlerForDistributedLockEvent");
}
m_lockWaitingOn = "We died so we can't ever get the distributed lock";
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
if (m_lockWaitingOn.equals(m_ourDistributedLockName) && m_currentParticipants == 0) {
// There are no more members still processing the last result
notifyDistributedLockWaiter();
}
else {
unlockLocalState();
}
}
else {
// lock was cancelled
unlockLocalState();
}
assert(!debugIsLocalStateLocked());
}
};
private void cancelDistributedLock() {
assert(debugIsLocalStateLocked());
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": cancelLockRequest for " + m_ourDistributedLockName);
}
assert(m_holdingDistributedLock);
try {
m_zk.delete(m_ourDistributedLockName, -1);
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in cancelDistributedLock");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in cancelDistributedLock");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in cancelDistributedLock");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in SynchronizedStatesManager.", true, e);
}
m_ourDistributedLockName = null;
m_holdingDistributedLock = false;
}
/*
* Warns about membership change notification waiting in the executor thread
*/
private void checkMembership() {
lockLocalState();
m_membershipChangePending = true;
unlockLocalState();
}
/*
* Callback notification from executor thread of membership change
*/
private void membershipChanged(Set knownHosts, Set addedMembers, Set removedMembers) {
lockLocalState();
// Even though we got a direct update, membership could have changed again between the
m_knownMembers = knownHosts;
m_membershipChangePending = false;
boolean notInitializing = m_requestedInitialState == null;
if (m_pendingProposal != null && m_memberResults != null &&
Sets.difference(m_knownMembers, m_memberResults).isEmpty()) {
// We can stop watching for results since we have a quorum.
processResultQuorum(m_memberResults);
}
else {
unlockLocalState();
}
if (notInitializing) {
try {
membershipChanged(addedMembers, removedMembers);
} catch (Exception e) {
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
assert(!debugIsLocalStateLocked());
}
/*
* Retrieves member set from ZooKeeper
*/
private void getLatestMembership() {
try {
m_knownMembers = ImmutableSet.copyOf(m_zk.getChildren(m_stateMachineMemberPath, null));
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in getLatestMembership");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in getLatestMembership");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in getLatestMembership");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in SynchronizedStatesManager.", true, e);
}
}
private void notifyDistributedLockWaiter() {
assert(debugIsLocalStateLocked());
assert(m_currentParticipants == 0);
m_holdingDistributedLock = true;
if (m_membershipChangePending) {
getLatestMembership();
}
if (m_requestedInitialState != null) {
// We are still waiting to initialize the state. Now that we have have the state lock we can
// look at the last set of results. We need to set proposedState so results will be checked.
assert(m_pendingProposal == null);
m_pendingProposal = m_requestedInitialState;
initializeFromActiveCommunity();
assert(!debugIsLocalStateLocked());
}
else {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Granted lockRequest for " + m_ourDistributedLockName);
}
m_lockWaitingOn = null;
unlockLocalState();
// Notify the derived class that the lock is available
try {
lockRequestCompleted();
} catch (Exception e) {
cancelLockRequest();
if (m_log.isDebugEnabled()) {
m_log.debug("Error in StateMachineInstance callbacks.", e);
}
m_initializationCompleted = false;
m_shared_es.submit(new CallbackExceptionHandler(this));
}
}
}
private boolean requestDistributedLock() {
try {
if (m_ourDistributedLockName != null) {
m_log.error(m_stateMachineId + ": Requested distributed lock before prior state change or task has been completed");
return false;
}
assert(debugIsLocalStateLocked());
m_ourDistributedLockName = m_zk.create(ZKUtil.joinZKPath(m_lockPath, "lock_"), null,
Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
m_lockWaitingOn = getNextLockNodeFromList();
if (m_lockWaitingOn.equals(m_ourDistributedLockName) && m_currentParticipants == 0) {
// Prevents a second notification.
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": requestLock successful for " + m_ourDistributedLockName);
}
m_lockWaitingOn = null;
m_holdingDistributedLock = true;
if (m_membershipChangePending) {
getLatestMembership();
}
return true;
}
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in requestDistributedLock");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in requestDistributedLock");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in requestDistributedLock");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
return false;
}
private void addResultEntry(byte result[]) {
try {
m_zk.create(m_myResultPath, result, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in addResultEntry");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in addResultEntry");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in addResultEntry");
}
}
catch (KeeperException.NodeExistsException e) {
// There is a race during initialization where a null result is assigned once so a current proposal
// is not hung. However, if a new proposal is submitted by another instance between that assignment
// and the call to checkForBarrierParticipantsChange, a second null result is assigned.
if (m_requestedInitialState == null || result != null) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine; Two results created for one proposal.", true, e);
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
}
private void assignStateChangeAgreement(boolean acceptable) {
assert(debugIsLocalStateLocked());
assert(m_pendingProposal != null);
assert(m_currentRequestType == REQUEST_TYPE.STATE_CHANGE_REQUEST);
byte result[] = new byte[1];
result[0] = (byte)(acceptable?1:0);
addResultEntry(result);
if (acceptable) {
// Since we are only interested in the results when we agree with the proposal
checkForBarrierResultsChanges();
}
else {
m_pendingProposal = null;
try {
// Since we don't care about the outcome remove ourself from the participant list
m_zk.delete(m_myParticipantPath, -1);
} catch (KeeperException.SessionExpiredException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received SessionExpiredException in assignStateChangeAgreement");
}
} catch (KeeperException.ConnectionLossException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received ConnectionLossException in assignStateChangeAgreement");
}
} catch (InterruptedException e) {
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Received InterruptedException in assignStateChangeAgreement");
}
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in StateMachine.", true, e);
}
unlockLocalState();
}
}
/*
* Returns true when this state machine is a full participant of the community and has the
* current state of the community
*/
protected boolean isInitialized() {
boolean initialized;
lockLocalState();
initialized = m_initializationCompleted && m_requestedInitialState == null;
unlockLocalState();
return initialized;
}
/*
* Notifies of full participation and the current agreed state
* warning: The ByteBuffer is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected abstract void setInitialState(ByteBuffer currentAgreedState);
/*
* Attempts to get the distributed lock. Returns true if the lock was acquired
*/
protected boolean requestLock() {
lockLocalState();
boolean rslt = false;
if (m_initializationCompleted) {
rslt = requestDistributedLock();
}
unlockLocalState();
return rslt;
}
/*
* Cancels an outstanding lock request. Should only be used if a previously desirable
* proposal is now obsolete (ie. use when lockRequestCompleted is called and a proposal
* is no longer necessary).
*/
protected void cancelLockRequest() {
lockLocalState();
if (m_initializationCompleted) {
assert (m_pendingProposal == null);
cancelDistributedLock();
}
unlockLocalState();
}
/*
* Notifies of the successful completion of a previous lock request
*/
protected void lockRequestCompleted() {}
/*
* Propose a new state. Only call after successful acquisition of the distributed lock.
*/
protected void proposeStateChange(ByteBuffer proposedState) {
assert(proposedState != null);
assert(proposedState.remaining() < Short.MAX_VALUE);
lockLocalState();
if (!m_initializationCompleted) {
unlockLocalState();
return;
}
// Only the lock owner can initiate a barrier request
assert(m_requestedInitialState == null);
if (proposedState.position() == 0) {
m_pendingProposal = proposedState;
}
else {
// Move to a new 0 aligned buffer
m_pendingProposal = ByteBuffer.allocate(proposedState.remaining());
m_pendingProposal.put(proposedState.array(),
proposedState.arrayOffset()+proposedState.position(), proposedState.remaining());
m_pendingProposal.flip();
}
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + ": Proposing new state " + stateToString(m_pendingProposal.asReadOnlyBuffer()));
}
m_stateChangeInitiator = true;
m_currentRequestType = REQUEST_TYPE.STATE_CHANGE_REQUEST;
ByteBuffer stateChange = buildProposal(REQUEST_TYPE.STATE_CHANGE_REQUEST,
m_synchronizedState.asReadOnlyBuffer(), m_pendingProposal.asReadOnlyBuffer());
m_lastProposalVersion = wakeCommunityWithProposal(stateChange.array());
assignStateChangeAgreement(true);
}
/*
* Notification of a new proposed state change by another member.
* warning: The ByteBuffer is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected void stateChangeProposed(ByteBuffer proposedState) {}
/*
* Called to accept or reject a new proposed state change by another member.
*/
protected void requestedStateChangeAcceptable(boolean acceptable) {
lockLocalState();
if (!m_initializationCompleted) {
unlockLocalState();
return;
}
assert(!m_stateChangeInitiator);
if (m_log.isDebugEnabled()) {
m_log.debug(m_stateMachineId + (acceptable ? ": Agrees with State proposal" :
": Disagrees with State proposal"));
}
assignStateChangeAgreement(acceptable);
}
/*
* Notification of the outcome of a previous state change proposal.
* warning: The ByteBuffer is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected void proposedStateResolved(boolean ourProposal, ByteBuffer proposedState, boolean success) {}
/*
* Propose a new task. Only call after successful acquisition of the distributed lock.
*/
protected void initiateCoordinatedTask(boolean correlated, ByteBuffer proposedTask) {
assert(proposedTask != null);
assert(proposedTask.remaining() < Short.MAX_VALUE);
lockLocalState();
if (m_initializationCompleted) {
// Only the lock owner can initiate a barrier request
assert (m_requestedInitialState == null);
if (proposedTask.position() == 0) {
m_pendingProposal = proposedTask;
} else {
// Move to a new 0 aligned buffer
m_pendingProposal = ByteBuffer.allocate(proposedTask.remaining());
m_pendingProposal.put(proposedTask.array(),
proposedTask.arrayOffset() + proposedTask.position(), proposedTask.remaining());
m_pendingProposal.flip();
}
if (m_log.isDebugEnabled()) {
if (m_pendingProposal.hasRemaining()) {
m_log.debug(m_stateMachineId + ": Requested new Task " + taskToString(m_pendingProposal.asReadOnlyBuffer()));
} else {
m_log.debug(m_stateMachineId + ": Requested unspecified new Task");
}
}
m_stateChangeInitiator = true;
m_currentRequestType = correlated ?
REQUEST_TYPE.CORRELATED_COORDINATED_TASK :
REQUEST_TYPE.UNCORRELATED_COORDINATED_TASK;
ByteBuffer taskProposal = buildProposal(m_currentRequestType,
m_synchronizedState.asReadOnlyBuffer(), proposedTask.asReadOnlyBuffer());
m_pendingProposal = proposedTask;
// Since we don't update m_lastProposalVersion, we will wake ourselves up
wakeCommunityWithProposal(taskProposal.array());
}
unlockLocalState();
}
/*
* Notification of a new task request by this member or another member.
* warning: The ByteBuffer is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected void taskRequested(ByteBuffer proposedTask) {}
/*
* Notification of a task request for newly joined members.
* warning: The ByteBuffer is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected void staleTaskRequestNotification(ByteBuffer proposedTask) {}
/*
* Called to accept or reject a new proposed state change by another member.
*/
protected void requestedTaskComplete(ByteBuffer result)
{
lockLocalState();
if (!m_initializationCompleted) {
unlockLocalState();
return;
}
assert(m_pendingProposal != null);
if (m_log.isDebugEnabled()) {
if (result.hasRemaining()) {
m_log.debug(m_stateMachineId + ": Local Task completed with result " +
taskResultToString(m_pendingProposal.asReadOnlyBuffer(), result.asReadOnlyBuffer()));
}
else {
m_log.debug(m_stateMachineId + ": Local Task completed with empty result");
}
}
addResultEntry(result.array());
checkForBarrierResultsChanges();
}
/*
* Notification of the outcome of the task by all members sorted by memberId.
* warning: The ByteBuffer taskRequest is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected void correlatedTaskCompleted(boolean ourTask, ByteBuffer taskRequest, Map results) {}
/*
* Notification of the outcome of the task by all members.
* warning: The ByteBuffer taskRequest is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected void uncorrelatedTaskCompleted(boolean ourTask, ByteBuffer taskRequest, List results) {}
/*
* Returns the current State. This request ignores pending proposals or outcomes. And may well be invalid as soon
* as the result is returned if a new proposed state is pending. To avoid this get the Distributed Lock first.
* warning: The ByteBuffer taskRequest is not guaranteed to start at position 0 (avoid rewind, flip, ...)
*/
protected ByteBuffer getCurrentState() {
ByteBuffer currentState;
lockLocalState();
if (m_initializationCompleted) {
currentState = m_synchronizedState.asReadOnlyBuffer();
}
else {
currentState = ByteBuffer.allocate(0);
}
unlockLocalState();
return currentState;
}
protected void membershipChanged(Set addedMembers, Set removedMembers) {}
protected Set getCurrentMembers() {
lockLocalState();
if (m_membershipChangePending) {
getLatestMembership();
}
Set latestAndGreatest = ImmutableSet.copyOf(m_knownMembers);
unlockLocalState();
return latestAndGreatest;
}
protected String getMemberId() {
return m_memberId;
}
/*
* Provides the version of the last received proposal or task.
* Note that the version number is not the number of state transitions but counts the total number of
* successful state transitions, failed state transitions, task requests, and last change outcome requests
*/
protected int getCurrentStateVersion() {
return m_lastProposalVersion;
}
protected boolean holdingDistributedLock() {
lockLocalState();
unlockLocalState();
return m_holdingDistributedLock;
}
protected abstract String stateToString(ByteBuffer state);
protected String taskToString(ByteBuffer task) { return ""; }
protected String taskResultToString(ByteBuffer task, ByteBuffer taskResult) { return ""; }
}
public SynchronizedStatesManager(ZooKeeper zk, String rootPath, String ssmNodeName, String memberId)
throws KeeperException, InterruptedException {
this(zk, rootPath, ssmNodeName, memberId, 1);
}
// Used only for Mocking StateMachineInstance
public SynchronizedStatesManager() {
m_zk = null;
m_registeredStateMachines = null;
m_ssmRootNode = "MockRootForZooKeeper";
m_stateMachineRoot = "MockRootForSSM";
m_stateMachineMemberPath = "MockRootMembershipNode";
m_memberId = "MockMemberId";
m_canonical_memberId = "MockCanonicalMemberId";
m_resetAllowance = 5;
m_resetLimit = m_resetAllowance;
}
public SynchronizedStatesManager(ZooKeeper zk, String rootPath, String ssmNodeName, String memberId, int registeredInstances)
throws KeeperException, InterruptedException {
this(zk, rootPath, ssmNodeName, memberId, registeredInstances, 5); // default resetAllowance is 5
}
public SynchronizedStatesManager(ZooKeeper zk, String rootPath, String ssmNodeName, String memberId, int registeredInstances, int resetAllowance)
throws KeeperException, InterruptedException {
m_zk = zk;
// We will not add ourselves as members in ZooKeeper until all StateMachineInstances have registered
m_registeredStateMachines = new StateMachineInstance[registeredInstances];
m_ssmRootNode = ssmNodeName;
m_stateMachineRoot = ZKUtil.joinZKPath(rootPath, ssmNodeName);
ByteBuffer numberOfInstances = ByteBuffer.allocate(4);
numberOfInstances.putInt(registeredInstances);
addIfMissing(m_stateMachineRoot, CreateMode.PERSISTENT, numberOfInstances.array());
m_stateMachineMemberPath = ZKUtil.joinZKPath(m_stateMachineRoot, m_memberNode);
m_canonical_memberId = memberId;
m_resetCounter = 0;
m_resetAllowance = resetAllowance;
m_resetLimit = m_resetAllowance;
m_memberId = m_canonical_memberId + "_v" + m_resetCounter;
}
public void ShutdownSynchronizedStatesManager() throws InterruptedException {
ListenableFuture disableComplete = m_shared_es.submit(disableInstances);
try {
disableComplete.get();
}
catch (ExecutionException e) {
Throwables.propagate(e.getCause());
}
}
private final Runnable disableInstances = new Runnable() {
@Override
public void run() {
try {
m_done.set(true);
for (StateMachineInstance stateMachine : m_registeredStateMachines) {
stateMachine.disableMembership();
}
m_zk.delete(ZKUtil.joinZKPath(m_stateMachineMemberPath, m_memberId), -1);
} catch (KeeperException.SessionExpiredException e) {
// lost the full connection. some test cases do this...
// means zk shutdown without the elector being shutdown.
// ignore.
} catch (KeeperException.ConnectionLossException e) {
// lost the full connection. some test cases do this...
// means shutdown without the elector being
// shutdown; ignore.
} catch (InterruptedException e) {
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in SynchronizedStatesManager.", true, e);
}
}
};
private final Runnable membershipEventHandler = new Runnable() {
@Override
public void run() {
try {
checkForMembershipChanges();
} catch (KeeperException.SessionExpiredException e) {
// lost the full connection. some test cases do this...
// means shutdown without the elector being
// shutdown; ignore.
} catch (KeeperException.ConnectionLossException e) {
// lost the full connection. some test cases do this...
// means shutdown without the elector being
// shutdown; ignore.
} catch (InterruptedException e) {
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in SynchronizedStatesManager.", true, e);
}
}
};
private class MembershipWatcher implements Watcher {
@Override
public void process(WatchedEvent event) {
try {
if (!m_done.get()) {
for (StateMachineInstance stateMachine : m_registeredStateMachines) {
stateMachine.checkMembership();
}
m_shared_es.submit(membershipEventHandler);
}
} catch (RejectedExecutionException e) {
}
}
}
private final MembershipWatcher m_membershipWatcher = new MembershipWatcher();
private final Runnable initializeInstances = new Runnable() {
@Override
public void run() {
try {
byte[] expectedInstances = m_zk.getData(m_stateMachineRoot, false, null);
assert(m_registeredStateMachineInstances == ByteBuffer.wrap(expectedInstances).getInt());
// First become a member of the community
addIfMissing(m_stateMachineMemberPath, CreateMode.PERSISTENT, null);
// This could fail because of an old ephemeral that has not aged out yet but assume this does not happen
addIfMissing(ZKUtil.joinZKPath(m_stateMachineMemberPath, m_memberId), CreateMode.EPHEMERAL, null);
m_groupMembers = ImmutableSet.copyOf(m_zk.getChildren(m_stateMachineMemberPath, m_membershipWatcher));
// Then initialize each instance
for (StateMachineInstance instance : m_registeredStateMachines) {
instance.initializeStateMachine(m_groupMembers);
}
} catch (KeeperException.SessionExpiredException e) {
// lost the full connection. some test cases do this...
// means zk shutdown without the elector being shutdown.
// ignore.
m_done.set(true);
} catch (KeeperException.ConnectionLossException e) {
// lost the full connection. some test cases do this...
// means shutdown without the elector being
// shutdown; ignore.
m_done.set(true);
} catch (InterruptedException e) {
m_done.set(true);
} catch (Exception e) {
org.voltdb.VoltDB.crashLocalVoltDB(
"Unexpected failure in initializeInstances.", true, e);
m_done.set(true);
}
}
};
private synchronized void registerStateMachine(StateMachineInstance machine) throws InterruptedException {
assert(m_registeredStateMachineInstances < m_registeredStateMachines.length);
m_registeredStateMachines[m_registeredStateMachineInstances] = (machine);
++m_registeredStateMachineInstances;
if (m_registeredStateMachineInstances == m_registeredStateMachines.length) {
if (machine.m_log.isDebugEnabled()) {
// lets make sure all the state machines are using unique paths
Set instanceNames = new HashSet();
for (StateMachineInstance instance : m_registeredStateMachines) {
if (!instanceNames.add(instance.m_statePath)) {
machine.m_log.error(": Multiple state machine instances with the same instanceName [" +
instance.m_statePath + "]");
}
}
}
// Do all the initialization and notifications on the executor to avoid a race with
// the group membership changes
ListenableFuture initComplete = m_shared_es.submit(initializeInstances);
try {
initComplete.get();
}
catch (ExecutionException e) {
Throwables.propagate(e.getCause());
}
}
}
private class CallbackExceptionHandler implements Runnable {
final StateMachineInstance m_directVictim;
CallbackExceptionHandler(StateMachineInstance directVictim) {
m_directVictim = directVictim;
}
@Override
public void run() {
// if the direct victim has already been reset, ignore the stale callback exception handling task
if (!m_directVictim.isInitializationCompleted()) {
assert (m_registeredStateMachineInstances > 0 && m_registeredStateMachineInstances == m_registeredStateMachines.length);
disableInstances.run();
if (m_lastResetTimeInMillis == -1L) {
m_lastResetTimeInMillis = System.currentTimeMillis();
} else {
long currentTimeInMillis = System.currentTimeMillis();
// if a full reset clear threshold duration has passed after last reset, bump the reset limit
if (currentTimeInMillis - m_lastResetTimeInMillis >= RESET_CLEAR_THRESHOLD) {
m_resetLimit = m_resetCounter + m_resetAllowance;
}
m_lastResetTimeInMillis = currentTimeInMillis;
}
++m_resetCounter;
if (m_resetCounter > m_resetLimit) {
return;
}
m_memberId = m_canonical_memberId + "_v" + m_resetCounter;
try {
for (StateMachineInstance instance : m_registeredStateMachines) {
instance.reset(instance == m_directVictim);
}
} catch (Exception e) {
return; // if something wrong happened in reset(), give up as if the reset limit is hit
}
m_done.set(false);
initializeInstances.run();
}
}
}
/*
* Track state machine membership. If it changes, notify all state machine instances
*/
private void checkForMembershipChanges() throws KeeperException, InterruptedException {
Set children = ImmutableSet.copyOf(m_zk.getChildren(m_stateMachineMemberPath, m_membershipWatcher));
Set removedMembers;
Set addedMembers;
if (m_registeredStateMachineInstances == m_registeredStateMachines.length && !m_groupMembers.equals(children)) {
removedMembers = Sets.difference(m_groupMembers, children);
addedMembers = Sets.difference(children, m_groupMembers);
m_groupMembers = children;
for (StateMachineInstance stateMachine : m_registeredStateMachines) {
stateMachine.membershipChanged(m_groupMembers, addedMembers, removedMembers);
}
}
}
}
