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A driver for Apache Cassandra 1.2+ that works exclusively with the Cassandra Query Language version 3
(CQL3) and Cassandra's binary protocol.
/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* Licensed 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 com.datastax.driver.core;
import com.codahale.metrics.Timer;
import com.datastax.driver.core.exceptions.*;
import com.datastax.driver.core.policies.RetryPolicy;
import com.datastax.driver.core.policies.RetryPolicy.RetryDecision.Type;
import com.datastax.driver.core.policies.SpeculativeExecutionPolicy.SpeculativeExecutionPlan;
import com.google.common.collect.Sets;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import io.netty.util.Timeout;
import io.netty.util.TimerTask;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetSocketAddress;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
/**
* Handles a request to cassandra, dealing with host failover and retries on
* unavailable/timeout.
*/
class RequestHandler {
private static final Logger logger = LoggerFactory.getLogger(RequestHandler.class);
final String id;
private final SessionManager manager;
private final Callback callback;
private final QueryPlan queryPlan;
private final SpeculativeExecutionPlan speculativeExecutionPlan;
private final boolean allowSpeculativeExecutions;
private final Set runningExecutions = Sets.newCopyOnWriteArraySet();
private final Set scheduledExecutions = Sets.newCopyOnWriteArraySet();
private final Statement statement;
private final io.netty.util.Timer scheduler;
private volatile List triedHosts;
private volatile ConcurrentMap errors;
private final Timer.Context timerContext;
private final long startTime;
private final AtomicBoolean isDone = new AtomicBoolean();
private final AtomicInteger executionCount = new AtomicInteger();
public RequestHandler(SessionManager manager, Callback callback, Statement statement) {
this.id = Long.toString(System.identityHashCode(this));
if (logger.isTraceEnabled())
logger.trace("[{}] {}", id, statement);
this.manager = manager;
this.callback = callback;
this.scheduler = manager.cluster.manager.connectionFactory.timer;
callback.register(this);
this.queryPlan = new QueryPlan(manager.loadBalancingPolicy().newQueryPlan(manager.poolsState.keyspace, statement));
this.speculativeExecutionPlan = manager.speculativeExecutionPolicy().newPlan(manager.poolsState.keyspace, statement);
this.allowSpeculativeExecutions = statement != Statement.DEFAULT
&& statement.isIdempotentWithDefault(manager.configuration().getQueryOptions());
this.statement = statement;
this.timerContext = metricsEnabled()
? metrics().getRequestsTimer().time()
: null;
this.startTime = System.nanoTime();
}
void sendRequest() {
startNewExecution();
}
// Called when the corresponding ResultSetFuture is cancelled by the client
void cancel() {
if (!isDone.compareAndSet(false, true))
return;
cancelPendingExecutions(null);
}
private void startNewExecution() {
if (isDone.get())
return;
Message.Request request = callback.request();
int position = executionCount.incrementAndGet();
SpeculativeExecution execution = new SpeculativeExecution(request, position);
runningExecutions.add(execution);
execution.findNextHostAndQuery();
}
private void scheduleExecution(long delayMillis) {
if (isDone.get() || delayMillis <= 0)
return;
if (logger.isTraceEnabled())
logger.trace("[{}] Schedule next speculative execution in {} ms", id, delayMillis);
scheduledExecutions.add(scheduler.newTimeout(newExecutionTask, delayMillis, TimeUnit.MILLISECONDS));
}
private final TimerTask newExecutionTask = new TimerTask() {
@Override
public void run(final Timeout timeout) throws Exception {
scheduledExecutions.remove(timeout);
if (!isDone.get())
// We're on the timer thread so reschedule to another executor
manager.executor().execute(new Runnable() {
@Override
public void run() {
if (metricsEnabled())
metrics().getErrorMetrics().getSpeculativeExecutions().inc();
startNewExecution();
}
});
}
};
private void cancelPendingExecutions(SpeculativeExecution ignore) {
for (SpeculativeExecution execution : runningExecutions)
if (execution != ignore) // not vital but this produces nicer logs
execution.cancel();
for (Timeout execution : scheduledExecutions)
execution.cancel();
}
private void setFinalResult(SpeculativeExecution execution, Connection connection, Message.Response response) {
if (!isDone.compareAndSet(false, true)) {
if (logger.isTraceEnabled())
logger.trace("[{}] Got beaten to setting the result", execution.id);
return;
}
if (logger.isTraceEnabled())
logger.trace("[{}] Setting final result", execution.id);
cancelPendingExecutions(execution);
try {
if (timerContext != null)
timerContext.stop();
ExecutionInfo info = execution.current.defaultExecutionInfo;
if (triedHosts != null) {
triedHosts.add(execution.current);
info = new ExecutionInfo(triedHosts);
}
if (execution.retryConsistencyLevel != null)
info = info.withAchievedConsistency(execution.retryConsistencyLevel);
if (response.getCustomPayload() != null)
info = info.withIncomingPayload(response.getCustomPayload());
callback.onSet(connection, response, info, statement, System.nanoTime() - startTime);
} catch (Exception e) {
callback.onException(connection,
new DriverInternalError("Unexpected exception while setting final result from " + response, e),
System.nanoTime() - startTime, /*unused*/0);
}
}
private void setFinalException(SpeculativeExecution execution, Connection connection, Exception exception) {
if (!isDone.compareAndSet(false, true)) {
if (logger.isTraceEnabled())
logger.trace("[{}] Got beaten to setting final exception", execution.id);
return;
}
if (logger.isTraceEnabled())
logger.trace("[{}] Setting final exception", execution.id);
cancelPendingExecutions(execution);
try {
if (timerContext != null)
timerContext.stop();
} finally {
callback.onException(connection, exception, System.nanoTime() - startTime, /*unused*/0);
}
}
// Triggered when an execution reaches the end of the query plan.
// This is only a failure if there are no other running executions.
private void reportNoMoreHosts(SpeculativeExecution execution) {
runningExecutions.remove(execution);
if (runningExecutions.isEmpty())
setFinalException(execution, null, new NoHostAvailableException(
errors == null ? Collections.emptyMap() : errors));
}
private boolean metricsEnabled() {
return manager.configuration().getMetricsOptions().isEnabled();
}
private Metrics metrics() {
return manager.cluster.manager.metrics;
}
private RetryPolicy retryPolicy() {
return statement.getRetryPolicy() == null
? manager.configuration().getPolicies().getRetryPolicy()
: statement.getRetryPolicy();
}
interface Callback extends Connection.ResponseCallback {
void onSet(Connection connection, Message.Response response, ExecutionInfo info, Statement statement, long latency);
void register(RequestHandler handler);
}
/**
* An execution of the query against the cluster.
* There is at least one instance per RequestHandler, and possibly more (depending on the SpeculativeExecutionPolicy).
* Each instance may retry on the same host, or on other hosts as defined by the RetryPolicy.
* All instances run concurrently and share the same query plan.
* There are three ways a SpeculativeExecution can stop:
* - it completes the query (with either a success or a fatal error), and reports the result to the RequestHandler
* - it gets cancelled, either because another execution completed the query, or because the RequestHandler was cancelled
* - it reaches the end of the query plan and informs the RequestHandler, which will decide what to do
*/
class SpeculativeExecution implements Connection.ResponseCallback {
final String id;
private final Message.Request request;
private volatile Host current;
private volatile ConsistencyLevel retryConsistencyLevel;
private final AtomicReference queryStateRef;
private final AtomicBoolean nextExecutionScheduled = new AtomicBoolean();
// This represents the number of times a retry has been triggered by the RetryPolicy (this is different from
// queryStateRef.get().retryCount, because some retries don't involve the policy, for example after an
// UNPREPARED response).
// This is incremented by one writer at a time, so volatile is good enough.
private volatile int retriesByPolicy;
private volatile Connection.ResponseHandler connectionHandler;
SpeculativeExecution(Message.Request request, int position) {
this.id = RequestHandler.this.id + "-" + position;
this.request = request;
this.queryStateRef = new AtomicReference(QueryState.INITIAL);
if (logger.isTraceEnabled())
logger.trace("[{}] Starting", id);
}
void findNextHostAndQuery() {
try {
Host host;
while (!isDone.get() && (host = queryPlan.next()) != null && !queryStateRef.get().isCancelled()) {
if (query(host))
return;
}
reportNoMoreHosts(this);
} catch (Exception e) {
// Shouldn't happen really, but if ever the loadbalancing policy returned iterator throws, we don't want to block.
setFinalException(null, new DriverInternalError("An unexpected error happened while sending requests", e));
}
}
private boolean query(final Host host) {
HostConnectionPool pool = manager.pools.get(host);
if (pool == null || pool.isClosed())
return false;
if (logger.isTraceEnabled())
logger.trace("[{}] Querying node {}", id, host);
if (allowSpeculativeExecutions && nextExecutionScheduled.compareAndSet(false, true))
scheduleExecution(speculativeExecutionPlan.nextExecution(host));
PoolingOptions poolingOptions = manager.configuration().getPoolingOptions();
ListenableFuture connectionFuture = pool.borrowConnection(
poolingOptions.getPoolTimeoutMillis(), TimeUnit.MILLISECONDS,
poolingOptions.getMaxQueueSize());
Futures.addCallback(connectionFuture, new FutureCallback() {
@Override
public void onSuccess(Connection connection) {
if (current != null) {
if (triedHosts == null)
triedHosts = new CopyOnWriteArrayList();
triedHosts.add(current);
}
current = host;
try {
write(connection, SpeculativeExecution.this);
} catch (ConnectionException e) {
// If we have any problem with the connection, move to the next node.
if (metricsEnabled())
metrics().getErrorMetrics().getConnectionErrors().inc();
if (connection != null)
connection.release();
logError(host.getSocketAddress(), e);
findNextHostAndQuery();
} catch (BusyConnectionException e) {
// The pool shouldn't have give us a busy connection unless we've maxed up the pool, so move on to the next host.
connection.release();
logError(host.getSocketAddress(), e);
findNextHostAndQuery();
} catch (RuntimeException e) {
if (connection != null)
connection.release();
logger.error("Unexpected error while querying " + host.getAddress(), e);
logError(host.getSocketAddress(), e);
findNextHostAndQuery();
}
}
@Override
public void onFailure(Throwable t) {
if (t instanceof BusyPoolException) {
logError(host.getSocketAddress(), t);
} else {
logger.error("Unexpected error while querying " + host.getAddress(), t);
logError(host.getSocketAddress(), t);
}
findNextHostAndQuery();
}
});
return true;
}
private void write(Connection connection, Connection.ResponseCallback responseCallback) throws ConnectionException, BusyConnectionException {
// Make sure cancel() does not see a stale connectionHandler if it sees the new query state
// before connection.write has completed
connectionHandler = null;
// Ensure query state is "in progress" (can be already if connection.write failed on a previous node and we're retrying)
while (true) {
QueryState previous = queryStateRef.get();
if (previous.isCancelled()) {
connection.release();
return;
}
if (previous.inProgress || queryStateRef.compareAndSet(previous, previous.startNext()))
break;
}
connectionHandler = connection.write(responseCallback, statement.getReadTimeoutMillis(), false);
// Only start the timeout when we're sure connectionHandler is set. This avoids an edge case where onTimeout() was triggered
// *before* the call to connection.write had returned.
connectionHandler.startTimeout();
// Note that we could have already received the response here (so onSet() / onException() would have been called). This is
// why we only test for CANCELLED_WHILE_IN_PROGRESS below.
// If cancel() was called after we set the state to "in progress", but before connection.write had completed, it might have
// missed the new value of connectionHandler. So make sure that cancelHandler() gets called here (we might call it twice,
// but it knows how to deal with it).
if (queryStateRef.get() == QueryState.CANCELLED_WHILE_IN_PROGRESS && connectionHandler.cancelHandler())
connection.release();
}
private RetryPolicy.RetryDecision computeRetryDecisionOnRequestError(DriverException exception) {
RetryPolicy.RetryDecision decision;
if (statement.isIdempotentWithDefault(manager.cluster.getConfiguration().getQueryOptions())) {
decision = retryPolicy().onRequestError(statement, request().consistency(), exception, retriesByPolicy);
} else {
decision = RetryPolicy.RetryDecision.rethrow();
}
if (metricsEnabled()) {
if (exception instanceof OperationTimedOutException) {
metrics().getErrorMetrics().getClientTimeouts().inc();
if (decision.getType() == Type.RETRY)
metrics().getErrorMetrics().getRetriesOnClientTimeout().inc();
if (decision.getType() == Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnClientTimeout().inc();
} else if (exception instanceof ConnectionException) {
metrics().getErrorMetrics().getConnectionErrors().inc();
if (decision.getType() == Type.RETRY)
metrics().getErrorMetrics().getRetriesOnConnectionError().inc();
if (decision.getType() == Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnConnectionError().inc();
} else {
metrics().getErrorMetrics().getOthers().inc();
if (decision.getType() == Type.RETRY)
metrics().getErrorMetrics().getRetriesOnOtherErrors().inc();
if (decision.getType() == Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnOtherErrors().inc();
}
}
return decision;
}
private void processRetryDecision(RetryPolicy.RetryDecision retryDecision, Connection connection, Exception exceptionToReport) {
switch (retryDecision.getType()) {
case RETRY:
retriesByPolicy++;
if (logger.isDebugEnabled())
logger.debug("[{}] Doing retry {} for query {} at consistency {}", id, retriesByPolicy, statement, retryDecision.getRetryConsistencyLevel());
if (metricsEnabled())
metrics().getErrorMetrics().getRetries().inc();
// log error for the current host if we are switching to another one
if (!retryDecision.isRetryCurrent())
logError(connection.address, exceptionToReport);
retry(retryDecision.isRetryCurrent(), retryDecision.getRetryConsistencyLevel());
break;
case RETHROW:
setFinalException(connection, exceptionToReport);
break;
case IGNORE:
if (metricsEnabled())
metrics().getErrorMetrics().getIgnores().inc();
setFinalResult(connection, new Responses.Result.Void());
break;
}
}
private void retry(final boolean retryCurrent, ConsistencyLevel newConsistencyLevel) {
final Host h = current;
if (newConsistencyLevel != null)
this.retryConsistencyLevel = newConsistencyLevel;
if (queryStateRef.get().isCancelled())
return;
if (!retryCurrent || !query(h))
findNextHostAndQuery();
}
private void logError(InetSocketAddress address, Throwable exception) {
logger.debug("[{}] Error querying {} : {}", id, address, exception.toString());
if (errors == null) {
synchronized (RequestHandler.this) {
if (errors == null) {
errors = new ConcurrentHashMap();
}
}
}
errors.put(address, exception);
}
void cancel() {
// Atomically set a special QueryState, that will cause any further operation to abort.
// We want to remember whether a request was in progress when we did this, so there are two cancel states.
while (true) {
QueryState previous = queryStateRef.get();
if (previous.isCancelled()) {
return;
} else if (previous.inProgress && queryStateRef.compareAndSet(previous, QueryState.CANCELLED_WHILE_IN_PROGRESS)) {
if (logger.isTraceEnabled())
logger.trace("[{}] Cancelled while in progress", id);
// The connectionHandler should be non-null, but we might miss the update if we're racing with write().
// If it's still null, this will be handled by re-checking queryStateRef at the end of write().
if (connectionHandler != null && connectionHandler.cancelHandler())
connectionHandler.connection.release();
return;
} else if (!previous.inProgress && queryStateRef.compareAndSet(previous, QueryState.CANCELLED_WHILE_COMPLETE)) {
if (logger.isTraceEnabled())
logger.trace("[{}] Cancelled while complete", id);
return;
}
}
}
@Override
public Message.Request request() {
if (retryConsistencyLevel != null && retryConsistencyLevel != request.consistency())
return request.copy(retryConsistencyLevel);
else
return request;
}
@Override
public void onSet(Connection connection, Message.Response response, long latency, int retryCount) {
QueryState queryState = queryStateRef.get();
if (!queryState.isInProgressAt(retryCount) ||
!queryStateRef.compareAndSet(queryState, queryState.complete())) {
logger.debug("onSet triggered but the response was completed by another thread, cancelling (retryCount = {}, queryState = {}, queryStateRef = {})",
retryCount, queryState, queryStateRef.get());
return;
}
Host queriedHost = current;
Exception exceptionToReport = null;
try {
switch (response.type) {
case RESULT:
connection.release();
setFinalResult(connection, response);
break;
case ERROR:
Responses.Error err = (Responses.Error) response;
exceptionToReport = err.asException(connection.address);
RetryPolicy.RetryDecision retry = null;
RetryPolicy retryPolicy = retryPolicy();
switch (err.code) {
case READ_TIMEOUT:
connection.release();
assert err.infos instanceof ReadTimeoutException;
ReadTimeoutException rte = (ReadTimeoutException) err.infos;
retry = retryPolicy.onReadTimeout(statement,
rte.getConsistencyLevel(),
rte.getRequiredAcknowledgements(),
rte.getReceivedAcknowledgements(),
rte.wasDataRetrieved(),
retriesByPolicy);
if (metricsEnabled()) {
metrics().getErrorMetrics().getReadTimeouts().inc();
if (retry.getType() == Type.RETRY)
metrics().getErrorMetrics().getRetriesOnReadTimeout().inc();
if (retry.getType() == Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnReadTimeout().inc();
}
break;
case WRITE_TIMEOUT:
connection.release();
assert err.infos instanceof WriteTimeoutException;
WriteTimeoutException wte = (WriteTimeoutException) err.infos;
if (statement.isIdempotentWithDefault(manager.cluster.getConfiguration().getQueryOptions()))
retry = retryPolicy.onWriteTimeout(statement,
wte.getConsistencyLevel(),
wte.getWriteType(),
wte.getRequiredAcknowledgements(),
wte.getReceivedAcknowledgements(),
retriesByPolicy);
else {
retry = RetryPolicy.RetryDecision.rethrow();
}
if (metricsEnabled()) {
metrics().getErrorMetrics().getWriteTimeouts().inc();
if (retry.getType() == Type.RETRY)
metrics().getErrorMetrics().getRetriesOnWriteTimeout().inc();
if (retry.getType() == Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnWriteTimeout().inc();
}
break;
case UNAVAILABLE:
connection.release();
assert err.infos instanceof UnavailableException;
UnavailableException ue = (UnavailableException) err.infos;
retry = retryPolicy.onUnavailable(statement,
ue.getConsistencyLevel(),
ue.getRequiredReplicas(),
ue.getAliveReplicas(),
retriesByPolicy);
if (metricsEnabled()) {
metrics().getErrorMetrics().getUnavailables().inc();
if (retry.getType() == Type.RETRY)
metrics().getErrorMetrics().getRetriesOnUnavailable().inc();
if (retry.getType() == Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnUnavailable().inc();
}
break;
case OVERLOADED:
connection.release();
assert exceptionToReport instanceof OverloadedException;
logger.warn("Host {} is overloaded.", connection.address);
retry = computeRetryDecisionOnRequestError((OverloadedException) exceptionToReport);
break;
case SERVER_ERROR:
connection.release();
assert exceptionToReport instanceof ServerError;
logger.warn("{} replied with server error ({}), defuncting connection.", connection.address, err.message);
// Defunct connection
connection.defunct(exceptionToReport);
retry = computeRetryDecisionOnRequestError((ServerError) exceptionToReport);
break;
case IS_BOOTSTRAPPING:
connection.release();
assert exceptionToReport instanceof BootstrappingException;
logger.error("Query sent to {} but it is bootstrapping. This shouldn't happen but trying next host.", connection.address);
if (metricsEnabled()) {
metrics().getErrorMetrics().getOthers().inc();
}
logError(connection.address, exceptionToReport);
retry(false, null);
return;
case UNPREPARED:
// Do not release connection yet, because we might reuse it to send the PREPARE message (see write() call below)
assert err.infos instanceof MD5Digest;
MD5Digest id = (MD5Digest) err.infos;
PreparedStatement toPrepare = manager.cluster.manager.preparedQueries.get(id);
if (toPrepare == null) {
// This shouldn't happen
connection.release();
String msg = String.format("Tried to execute unknown prepared query %s", id);
logger.error(msg);
setFinalException(connection, new DriverInternalError(msg));
return;
}
String currentKeyspace = connection.keyspace();
String prepareKeyspace = toPrepare.getQueryKeyspace();
if (prepareKeyspace != null && (currentKeyspace == null || !currentKeyspace.equals(prepareKeyspace))) {
// This shouldn't happen in normal use, because a user shouldn't try to execute
// a prepared statement with the wrong keyspace set.
// Fail fast (we can't change the keyspace to reprepare, because we're using a pooled connection
// that's shared with other requests).
connection.release();
throw new IllegalStateException(String.format("Statement was prepared on keyspace %s, can't execute it on %s (%s)",
toPrepare.getQueryKeyspace(), connection.keyspace(), toPrepare.getQueryString()));
}
logger.info("Query {} is not prepared on {}, preparing before retrying executing. "
+ "Seeing this message a few times is fine, but seeing it a lot may be source of performance problems",
toPrepare.getQueryString(), connection.address);
write(connection, prepareAndRetry(toPrepare.getQueryString()));
// we're done for now, the prepareAndRetry callback will handle the rest
return;
default:
connection.release();
if (metricsEnabled())
metrics().getErrorMetrics().getOthers().inc();
break;
}
if (retry == null)
setFinalResult(connection, response);
else {
processRetryDecision(retry, connection, exceptionToReport);
}
break;
default:
connection.release();
setFinalResult(connection, response);
break;
}
} catch (Exception e) {
exceptionToReport = e;
setFinalException(connection, e);
} finally {
if (queriedHost != null && statement != Statement.DEFAULT) {
manager.cluster.manager.reportQuery(queriedHost, statement, exceptionToReport, latency);
}
}
}
private Connection.ResponseCallback prepareAndRetry(final String toPrepare) {
// do not bother inspecting retry policy at this step, no other decision
// makes sense than retry on the same host if the query was prepared,
// or on another host, if an error/timeout occurred.
// The original request hasn't been executed so far, so there is no risk
// of re-executing non-idempotent statements.
return new Connection.ResponseCallback() {
@Override
public Message.Request request() {
Requests.Prepare request = new Requests.Prepare(toPrepare);
// propagate the original custom payload in the prepare request
request.setCustomPayload(statement.getOutgoingPayload());
return request;
}
@Override
public int retryCount() {
return SpeculativeExecution.this.retryCount();
}
@Override
public void onSet(Connection connection, Message.Response response, long latency, int retryCount) {
QueryState queryState = queryStateRef.get();
if (!queryState.isInProgressAt(retryCount) ||
!queryStateRef.compareAndSet(queryState, queryState.complete())) {
logger.debug("onSet triggered but the response was completed by another thread, cancelling (retryCount = {}, queryState = {}, queryStateRef = {})",
retryCount, queryState, queryStateRef.get());
return;
}
connection.release();
switch (response.type) {
case RESULT:
if (((Responses.Result) response).kind == Responses.Result.Kind.PREPARED) {
logger.debug("Scheduling retry now that query is prepared");
retry(true, null);
} else {
logError(connection.address, new DriverException("Got unexpected response to prepare message: " + response));
retry(false, null);
}
break;
case ERROR:
logError(connection.address, new DriverException("Error preparing query, got " + response));
if (metricsEnabled())
metrics().getErrorMetrics().getOthers().inc();
retry(false, null);
break;
default:
// Something's wrong, so we return but we let setFinalResult propagate the exception
SpeculativeExecution.this.setFinalResult(connection, response);
break;
}
}
@Override
public void onException(Connection connection, Exception exception, long latency, int retryCount) {
SpeculativeExecution.this.onException(connection, exception, latency, retryCount);
}
@Override
public boolean onTimeout(Connection connection, long latency, int retryCount) {
QueryState queryState = queryStateRef.get();
if (!queryState.isInProgressAt(retryCount) ||
!queryStateRef.compareAndSet(queryState, queryState.complete())) {
logger.debug("onTimeout triggered but the response was completed by another thread, cancelling (retryCount = {}, queryState = {}, queryStateRef = {})",
retryCount, queryState, queryStateRef.get());
return false;
}
connection.release();
logError(connection.address, new OperationTimedOutException(connection.address, "Timed out waiting for response to PREPARE message"));
retry(false, null);
return true;
}
};
}
@Override
public void onException(Connection connection, Exception exception, long latency, int retryCount) {
QueryState queryState = queryStateRef.get();
if (!queryState.isInProgressAt(retryCount) ||
!queryStateRef.compareAndSet(queryState, queryState.complete())) {
logger.debug("onException triggered but the response was completed by another thread, cancelling (retryCount = {}, queryState = {}, queryStateRef = {})",
retryCount, queryState, queryStateRef.get());
return;
}
Host queriedHost = current;
try {
connection.release();
if (exception instanceof ConnectionException) {
RetryPolicy.RetryDecision decision = computeRetryDecisionOnRequestError((ConnectionException) exception);
processRetryDecision(decision, connection, exception);
return;
}
setFinalException(connection, exception);
} catch (Exception e) {
// This shouldn't happen, but if it does, we want to signal the callback, not let it hang indefinitely
setFinalException(null, new DriverInternalError("An unexpected error happened while handling exception " + exception, e));
} finally {
if (queriedHost != null && statement != Statement.DEFAULT)
manager.cluster.manager.reportQuery(queriedHost, statement, exception, latency);
}
}
@Override
public boolean onTimeout(Connection connection, long latency, int retryCount) {
QueryState queryState = queryStateRef.get();
if (!queryState.isInProgressAt(retryCount) ||
!queryStateRef.compareAndSet(queryState, queryState.complete())) {
logger.debug("onTimeout triggered but the response was completed by another thread, cancelling (retryCount = {}, queryState = {}, queryStateRef = {})",
retryCount, queryState, queryStateRef.get());
return false;
}
Host queriedHost = current;
OperationTimedOutException timeoutException = new OperationTimedOutException(connection.address, "Timed out waiting for server response");
try {
connection.release();
RetryPolicy.RetryDecision decision = computeRetryDecisionOnRequestError(timeoutException);
processRetryDecision(decision, connection, timeoutException);
} catch (Exception e) {
// This shouldn't happen, but if it does, we want to signal the callback, not let it hang indefinitely
setFinalException(null, new DriverInternalError("An unexpected error happened while handling timeout", e));
} finally {
if (queriedHost != null && statement != Statement.DEFAULT)
manager.cluster.manager.reportQuery(queriedHost, statement, timeoutException, latency);
}
return true;
}
@Override
public int retryCount() {
return queryStateRef.get().retryCount;
}
private void setFinalException(Connection connection, Exception exception) {
RequestHandler.this.setFinalException(this, connection, exception);
}
private void setFinalResult(Connection connection, Message.Response response) {
RequestHandler.this.setFinalResult(this, connection, response);
}
}
/**
* The state of a SpeculativeExecution.
*
* This is used to prevent races between request completion (either success or error) and timeout.
* A retry is in progress once we have written the request to the connection and until we get back a response (see onSet
* or onException) or a timeout (see onTimeout).
* The count increments on each retry.
*/
static class QueryState {
static final QueryState INITIAL = new QueryState(-1, false);
static final QueryState CANCELLED_WHILE_IN_PROGRESS = new QueryState(Integer.MIN_VALUE, false);
static final QueryState CANCELLED_WHILE_COMPLETE = new QueryState(Integer.MIN_VALUE + 1, false);
final int retryCount;
final boolean inProgress;
private QueryState(int count, boolean inProgress) {
this.retryCount = count;
this.inProgress = inProgress;
}
boolean isInProgressAt(int retryCount) {
return inProgress && this.retryCount == retryCount;
}
QueryState complete() {
assert inProgress;
return new QueryState(retryCount, false);
}
QueryState startNext() {
assert !inProgress;
return new QueryState(retryCount + 1, true);
}
public boolean isCancelled() {
return this == CANCELLED_WHILE_IN_PROGRESS || this == CANCELLED_WHILE_COMPLETE;
}
@Override
public String toString() {
return String.format("QueryState(count=%d, inProgress=%s, cancelled=%s)", retryCount, inProgress, isCancelled());
}
}
/**
* Wraps the iterator return by {@link com.datastax.driver.core.policies.LoadBalancingPolicy} to make it safe for
* concurrent access by multiple threads.
*/
static class QueryPlan {
private final Iterator iterator;
QueryPlan(Iterator iterator) {
this.iterator = iterator;
}
/**
* @return null if there are no more hosts
*/
synchronized Host next() {
return iterator.hasNext() ? iterator.next() : null;
}
}
}