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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.procedure;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import org.apache.hadoop.hbase.errorhandling.ForeignException;
import org.apache.hadoop.hbase.errorhandling.ForeignExceptionDispatcher;
import org.apache.hadoop.hbase.errorhandling.ForeignExceptionListener;
import org.apache.hadoop.hbase.errorhandling.ForeignExceptionSnare;
import org.apache.hadoop.hbase.errorhandling.TimeoutExceptionInjector;
import org.apache.zookeeper.KeeperException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Distributed procedure member's Subprocedure. A procedure is sarted on a ProcedureCoordinator
* which communicates with ProcedureMembers who create and start its part of the Procedure. This
* sub part is called a Subprocedure
*
* Users should subclass this and implement {@link #acquireBarrier()} (get local barrier for this
* member), {@link #insideBarrier()} (execute while globally barriered and release barrier) and
* {@link #cleanup(Exception)} (release state associated with subprocedure.)
*
* When submitted to a ProcedureMemeber, the call method is executed in a separate thread.
* Latches are use too block its progress and trigger continuations when barrier conditions are
* met.
*
* Exception that makes it out of calls to {@link #acquireBarrier()} or {@link #insideBarrier()}
* gets converted into {@link ForeignException}, which will get propagated to the
* {@link ProcedureCoordinator}.
*
* There is a category of procedure (ex: online-snapshots), and a user-specified instance-specific
* barrierName. (ex: snapshot121126).
*/
abstract public class Subprocedure implements Callable {
private static final Logger LOG = LoggerFactory.getLogger(Subprocedure.class);
// Name of the procedure
final private String barrierName;
//
// Execution state
//
/** wait on before allowing the in barrier phase to proceed */
private final CountDownLatch inGlobalBarrier;
/** counted down when the Subprocedure has completed */
private final CountDownLatch releasedLocalBarrier;
//
// Error handling
//
/** monitor to check for errors */
protected final ForeignExceptionDispatcher monitor;
/** frequency to check for errors (ms) */
protected final long wakeFrequency;
protected final TimeoutExceptionInjector executionTimeoutTimer;
protected final ProcedureMemberRpcs rpcs;
private volatile boolean complete = false;
/**
* @param member reference to the member managing this subprocedure
* @param procName name of the procedure this subprocedure is associated with
* @param monitor notified if there is an error in the subprocedure
* @param wakeFrequency time in millis to wake to check if there is an error via the monitor (in
* milliseconds).
* @param timeout time in millis that will trigger a subprocedure abort if it has not completed
*/
public Subprocedure(ProcedureMember member, String procName, ForeignExceptionDispatcher monitor,
long wakeFrequency, long timeout) {
// Asserts should be caught during unit testing
assert member != null : "procedure member should be non-null";
assert member.getRpcs() != null : "rpc handlers should be non-null";
assert procName != null : "procedure name should be non-null";
assert monitor != null : "monitor should be non-null";
// Default to a very large timeout
this.rpcs = member.getRpcs();
this.barrierName = procName;
this.monitor = monitor;
// forward any failures to coordinator. Since this is a dispatcher, resend loops should not be
// possible.
this.monitor.addListener(new ForeignExceptionListener() {
@Override
public void receive(ForeignException ee) {
// if this is a notification from a remote source, just log
if (ee.isRemote()) {
LOG.debug("Was remote foreign exception, not redispatching error", ee);
return;
}
// if this is a local KeeperException, don't attempt to notify other members
if (ee.getCause() instanceof KeeperException) {
LOG.debug("Was KeeperException, not redispatching error", ee);
return;
}
// if it is other local error, then send it to the coordinator
try {
rpcs.sendMemberAborted(Subprocedure.this, ee);
} catch (IOException e) {
// this will fail all the running procedures, since the connection is down
LOG.error("Can't reach controller, not propagating error", e);
}
}
});
this.wakeFrequency = wakeFrequency;
this.inGlobalBarrier = new CountDownLatch(1);
this.releasedLocalBarrier = new CountDownLatch(1);
// accept error from timer thread, this needs to be started.
this.executionTimeoutTimer = new TimeoutExceptionInjector(monitor, timeout);
}
public String getName() {
return barrierName;
}
public String getMemberName() {
return rpcs.getMemberName();
}
private void rethrowException() throws ForeignException {
monitor.rethrowException();
}
/**
* Execute the Subprocedure {@link #acquireBarrier()} and {@link #insideBarrier()} methods
* while keeping some state for other threads to access.
*
* This would normally be executed by the ProcedureMemeber when a acquire message comes from the
* coordinator. Rpcs are used to spend message back to the coordinator after different phases
* are executed. Any exceptions caught during the execution (except for InterruptedException) get
* converted and propagated to coordinator via {@link ProcedureMemberRpcs#sendMemberAborted(
* Subprocedure, ForeignException)}.
*/
@SuppressWarnings("finally")
final public Void call() {
LOG.debug("Starting subprocedure '" + barrierName + "' with timeout " +
executionTimeoutTimer.getMaxTime() + "ms");
// start the execution timeout timer
executionTimeoutTimer.start();
try {
// start by checking for error first
rethrowException();
LOG.debug("Subprocedure '" + barrierName + "' starting 'acquire' stage");
acquireBarrier();
LOG.debug("Subprocedure '" + barrierName + "' locally acquired");
rethrowException();
// vote yes to coordinator about being prepared
rpcs.sendMemberAcquired(this);
LOG.debug("Subprocedure '" + barrierName + "' coordinator notified of 'acquire', waiting on" +
" 'reached' or 'abort' from coordinator");
// wait for the procedure to reach global barrier before proceding
waitForReachedGlobalBarrier();
rethrowException(); // if Coordinator aborts, will bail from here with exception
// In traditional 2PC, if a member reaches this state the TX has been committed and the
// member is responsible for rolling forward and recovering and completing the subsequent
// operations in the case of failure. It cannot rollback.
//
// This implementation is not 2PC since it can still rollback here, and thus has different
// semantics.
LOG.debug("Subprocedure '" + barrierName + "' received 'reached' from coordinator.");
byte[] dataToCoordinator = insideBarrier();
LOG.debug("Subprocedure '" + barrierName + "' locally completed");
rethrowException();
// Ack that the member has executed and released local barrier
rpcs.sendMemberCompleted(this, dataToCoordinator);
LOG.debug("Subprocedure '" + barrierName + "' has notified controller of completion");
// make sure we didn't get an external exception
rethrowException();
} catch (Exception e) {
String msg = null;
if (e instanceof InterruptedException) {
msg = "Procedure '" + barrierName + "' aborting due to interrupt!" +
" Likely due to pool shutdown.";
Thread.currentThread().interrupt();
} else if (e instanceof ForeignException) {
msg = "Subprocedure '" + barrierName + "' aborting due to a ForeignException!";
} else {
msg = "Subprocedure '" + barrierName + "' failed!";
}
cancel(msg, e);
LOG.debug("Subprocedure '" + barrierName + "' running cleanup.");
cleanup(e);
} finally {
releasedLocalBarrier.countDown();
// tell the timer we are done, if we get here successfully
executionTimeoutTimer.complete();
complete = true;
LOG.debug("Subprocedure '" + barrierName + "' completed.");
return null;
}
}
boolean isComplete() {
return complete;
}
/**
* exposed for testing.
*/
ForeignExceptionSnare getErrorCheckable() {
return this.monitor;
}
/**
* The implementation of this method should gather and hold required resources (locks, disk
* space, etc) to satisfy the Procedures barrier condition. For example, this would be where
* to make all the regions on a RS on the quiescent for an procedure that required all regions
* to be globally quiesed.
*
* Users should override this method. If a quiescent is not required, this is overkill but
* can still be used to execute a procedure on all members and to propagate any exceptions.
*
* @throws ForeignException
*/
abstract public void acquireBarrier() throws ForeignException;
/**
* The implementation of this method should act with the assumption that the barrier condition
* has been satisfied. Continuing the previous example, a condition could be that all RS's
* globally have been quiesced, and procedures that require this precondition could be
* implemented here.
* The implementation should also collect the result of the subprocedure as data to be returned
* to the coordinator upon successful completion.
* Users should override this method.
* @return the data the subprocedure wants to return to coordinator side.
* @throws ForeignException
*/
abstract public byte[] insideBarrier() throws ForeignException;
/**
* Users should override this method. This implementation of this method should rollback and
* cleanup any temporary or partially completed state that the {@link #acquireBarrier()} may have
* created.
* @param e
*/
abstract public void cleanup(Exception e);
/**
* Method to cancel the Subprocedure by injecting an exception from and external source.
* @param cause
*/
public void cancel(String msg, Throwable cause) {
LOG.error(msg, cause);
complete = true;
if (cause instanceof ForeignException) {
monitor.receive((ForeignException) cause);
} else {
monitor.receive(new ForeignException(getMemberName(), cause));
}
}
/**
* Callback for the member rpcs to call when the global barrier has been reached. This
* unblocks the main subprocedure exectuion thread so that the Subprocedure's
* {@link #insideBarrier()} method can be run.
*/
public void receiveReachedGlobalBarrier() {
inGlobalBarrier.countDown();
}
//
// Subprocedure Internal State interface
//
/**
* Wait for the reached global barrier notification.
*
* Package visibility for testing
*
* @throws ForeignException
* @throws InterruptedException
*/
void waitForReachedGlobalBarrier() throws ForeignException, InterruptedException {
Procedure.waitForLatch(inGlobalBarrier, monitor, wakeFrequency,
barrierName + ":remote acquired");
}
/**
* Waits until the entire procedure has globally completed, or has been aborted.
* @throws ForeignException
* @throws InterruptedException
*/
public void waitForLocallyCompleted() throws ForeignException, InterruptedException {
Procedure.waitForLatch(releasedLocalBarrier, monitor, wakeFrequency,
barrierName + ":completed");
}
/**
* Empty Subprocedure for testing.
*
* Must be public for stubbing used in testing to work.
*/
public static class SubprocedureImpl extends Subprocedure {
public SubprocedureImpl(ProcedureMember member, String opName,
ForeignExceptionDispatcher monitor, long wakeFrequency, long timeout) {
super(member, opName, monitor, wakeFrequency, timeout);
}
@Override
public void acquireBarrier() throws ForeignException {}
@Override
public byte[] insideBarrier() throws ForeignException {
return new byte[0];
}
@Override
public void cleanup(Exception e) {}
};
}