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A driver for DataStax Enterprise (DSE)
and Apache Cassandra 1.2+ clusters that works exclusively with the
Cassandra Query Language version 3 (CQL3) and Cassandra's binary protocol,
supporting DSE-specific features such as geospatial types, DSE Graph and DSE authentication.
/*
* Copyright (C) 2012-2017 DataStax Inc.
*
* This software can be used solely with DataStax Enterprise. Please consult the license at
* http://www.datastax.com/terms/datastax-dse-driver-license-terms
*/
package com.datastax.driver.core;
import com.codahale.metrics.Timer;
import com.datastax.driver.core.Message.Request;
import com.datastax.driver.core.RequestHandler.QueryPlan;
import com.datastax.driver.core.RequestHandler.QueryState;
import com.datastax.driver.core.exceptions.*;
import com.datastax.driver.core.policies.RetryPolicy;
import com.datastax.driver.core.utils.MoreFutures;
import com.google.common.base.Function;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetSocketAddress;
import java.util.Collections;
import java.util.List;
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.AtomicReference;
/**
* Handles a request that supports multiple response messages.
*
* This is similar to {@link RequestHandler}, but with the following differences:
*
* - the connection is not released after the first request. The caller must invoke {@link #release()} when it detects
* that the request has finished executing on the server;
* - speculative executions are not supported.
*
*/
class MultiResponseRequestHandler implements Connection.ResponseCallback {
private static final Logger logger = LoggerFactory.getLogger(MultiResponseRequestHandler.class);
private final String id;
final SessionManager manager;
private final Callback callback;
private final Message.Request initialRequest;
final Statement statement;
private final QueryPlan queryPlan;
final int timeoutMillis;
private final Timer.Context timerContext;
private final AtomicReference queryStateRef;
private volatile List triedHosts;
private volatile ConcurrentMap errors;
private volatile Host current;
private volatile Connection connection;
private volatile Connection.ResponseHandler connectionHandler;
private volatile ConsistencyLevel retryConsistencyLevel;
// 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 ExecutionInfo info;
private volatile boolean gotFirstResult;
MultiResponseRequestHandler(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.initialRequest = callback.getRequest();
this.statement = statement;
this.queryPlan = new QueryPlan(manager.loadBalancingPolicy().newQueryPlan(manager.poolsState.keyspace, statement));
this.timeoutMillis = statement.getReadTimeoutMillis() >= 0
? statement.getReadTimeoutMillis()
: manager.configuration().getSocketOptions().getReadTimeoutMillis();
this.timerContext = metricsEnabled()
? metrics().getRequestsTimer().time()
: null;
this.queryStateRef = new AtomicReference(QueryState.INITIAL);
callback.register(this);
}
private boolean metricsEnabled() {
return manager.configuration().getMetricsOptions().isEnabled();
}
private Metrics metrics() {
return manager.cluster.manager.metrics;
}
void sendRequest() {
try {
Host host;
while ((host = queryPlan.next()) != null && !queryStateRef.get().isCancelled()) {
if (query(host))
return;
}
reportNoMoreHosts();
} catch (Exception e) {
// Shouldn't happen really, but if ever the loadbalancing policy returned iterator throws, we don't want to block.
setException(null, new DriverInternalError("An unexpected error happened while sending requests", e), false);
}
}
/**
* Release the local resources associated with the request.
*
* This should be called only when the caller detects that the request has finished running server-side, such as
* after the last page.
*
* To stop a query that is still running, use {@link #cancel()}.
*/
void release() {
release(connection);
if (timerContext != null) {
timerContext.stop();
}
}
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);
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) {
MultiResponseRequestHandler.this.connection = connection;
if (current != null) {
if (triedHosts == null) {
triedHosts = new CopyOnWriteArrayList();
}
triedHosts.add(current);
}
current = host;
try {
write(connection, MultiResponseRequestHandler.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);
sendRequest();
} 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);
sendRequest();
} catch (RuntimeException e) {
if (connection != null)
connection.release();
logger.error("Unexpected error while querying " + host.getAddress(), e);
logError(host.getSocketAddress(), e);
sendRequest();
}
}
@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);
}
sendRequest();
}
});
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()) {
release(connection);
return;
}
if (previous.inProgress || queryStateRef.compareAndSet(previous, previous.startNext()))
break;
}
connectionHandler = connection.write(responseCallback, statement.getReadTimeoutMillis(), false, true);
// 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();
}
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 == QueryState.INITIAL && queryStateRef.compareAndSet(previous, QueryState.CANCELLED_WHILE_COMPLETE)) {
// Nothing was sent to the server yet, so nothing to do
logger.trace("[{}] Cancelled before the first request was sent", id);
return;
} else if (previous.inProgress && queryStateRef.compareAndSet(previous, QueryState.CANCELLED_WHILE_IN_PROGRESS)) {
logger.trace("[{}] Cancelled during the initial request", id);
// Contrary to single-response requests (see RequestHandler), we don't remove the handler right away,
// because the server could still send more than one response after the cancellation, causing
// Connection.Dispatcher.channelRead0 to release the streamId too soon. We only remove the handler when
// we receive the last response, or when the cancel request succeeds.
sendCancelRequest();
return;
} else if (!previous.inProgress && queryStateRef.compareAndSet(previous, QueryState.CANCELLED_WHILE_COMPLETE)) {
logger.trace("[{}] Cancelled after initial request complete", id);
sendCancelRequest();
return;
}
}
}
private void sendCancelRequest() {
final Connection.ResponseCallback cancelResponseCallback = new Connection.ResponseCallback() {
@Override
public Request request() {
return callback.getCancelRequest(connectionHandler.streamId);
}
@Override
public void onSet(Connection connection, Message.Response response, long latency, int retryCount) {
logger.trace("[{}] Cancelled successfully");
connection.release(); // for the stream of the cancel request
MultiResponseRequestHandler.this.release(); // for the stream of the continuous query
}
@Override
public void onException(Connection connection, Exception exception, long latency, int retryCount) {
logger.warn("[" + id + "] Cancel request failed. " +
"This is not critical (the request will eventually time out server-side).", exception);
connection.release();
}
@Override
public boolean onTimeout(Connection connection, long latency, int retryCount) {
logger.warn("[{}] Cancel request timed out " +
"This is not critical (the request will eventually time out server-side).", id);
connection.release();
return false;
}
@Override
public int retryCount() {
return 0;
}
};
ListenableFuture futureWrite = Futures.transform(
// Borrow again, because the cancel request uses a different streamId
manager.pools.get(current).borrowConnection(0, TimeUnit.MILLISECONDS, 0),
new Function() {
@Override
public Void apply(Connection c) {
logger.trace("[{}] Sending cancel request" + id);
connection.write(cancelResponseCallback, timeoutMillis, true, false);
return null;
}
});
Futures.addCallback(futureWrite, new MoreFutures.FailureCallback() {
@Override
public void onFailure(Throwable t) {
logger.warn("[" + id + "] Error writing cancel request. " +
"This is not critical (the request will eventually time out server-side).", t);
}
});
}
private void release(Connection connection) {
if (connectionHandler != null) {
connectionHandler.cancelHandler();
}
connection.release();
}
@Override
public Request request() {
if (retryConsistencyLevel != null && retryConsistencyLevel != initialRequest.consistency())
return initialRequest.copy(retryConsistencyLevel);
else
return initialRequest;
}
@Override
public void onSet(Connection connection, Message.Response response, long latency, int retryCount) {
QueryState queryState = queryStateRef.get();
if (!gotFirstResult) {
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;
}
}
Exception exceptionToReport;
try {
switch (response.type) {
case RESULT:
setResult(connection, response);
break;
case ERROR:
Responses.Error err = (Responses.Error) response;
exceptionToReport = err.asException(connection.address);
RetryPolicy.RetryDecision retry = null;
// Retries are only handled for the first response. For subsequent responses, errors will always
// be reported directly.
if (!gotFirstResult) {
RetryPolicy retryPolicy = retryPolicy();
switch (err.code) {
case READ_TIMEOUT:
release(connection);
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() == RetryPolicy.RetryDecision.Type.RETRY)
metrics().getErrorMetrics().getRetriesOnReadTimeout().inc();
if (retry.getType() == RetryPolicy.RetryDecision.Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnReadTimeout().inc();
}
break;
case WRITE_TIMEOUT:
release(connection);
assert err.infos instanceof WriteTimeoutException;
WriteTimeoutException wte = (WriteTimeoutException) err.infos;
String msg = String.format("Unexpected error for %s, multi-response query are expected to be read-only", id);
logger.error(msg, wte);
setException(connection, new DriverInternalError(msg, wte), true);
break;
case UNAVAILABLE:
release(connection);
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() == RetryPolicy.RetryDecision.Type.RETRY)
metrics().getErrorMetrics().getRetriesOnUnavailable().inc();
if (retry.getType() == RetryPolicy.RetryDecision.Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnUnavailable().inc();
}
break;
case OVERLOADED:
release(connection);
assert exceptionToReport instanceof OverloadedException;
logger.warn("Host {} is overloaded.", connection.address);
retry = computeRetryDecisionOnRequestError((OverloadedException) exceptionToReport);
break;
case SERVER_ERROR:
release(connection);
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
release(connection);
msg = String.format("Tried to execute unknown prepared query %s", id);
logger.error(msg);
setException(connection, new DriverInternalError(msg), true);
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).
release(connection);
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:
release(connection);
if (metricsEnabled())
metrics().getErrorMetrics().getOthers().inc();
break;
}
}
if (retry == null)
setResult(connection, response);
else {
processRetryDecision(retry, connection, exceptionToReport, true);
}
break;
default:
connection.release();
setResult(connection, response);
break;
}
} catch (Exception e) {
setException(connection, e, false);
}
}
private RetryPolicy retryPolicy() {
return statement.getRetryPolicy() == null
? manager.configuration().getPolicies().getRetryPolicy()
: statement.getRetryPolicy();
}
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() == RetryPolicy.RetryDecision.Type.RETRY)
metrics().getErrorMetrics().getRetriesOnClientTimeout().inc();
if (decision.getType() == RetryPolicy.RetryDecision.Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnClientTimeout().inc();
} else if (exception instanceof ConnectionException) {
metrics().getErrorMetrics().getConnectionErrors().inc();
if (decision.getType() == RetryPolicy.RetryDecision.Type.RETRY)
metrics().getErrorMetrics().getRetriesOnConnectionError().inc();
if (decision.getType() == RetryPolicy.RetryDecision.Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnConnectionError().inc();
} else {
metrics().getErrorMetrics().getOthers().inc();
if (decision.getType() == RetryPolicy.RetryDecision.Type.RETRY)
metrics().getErrorMetrics().getRetriesOnOtherErrors().inc();
if (decision.getType() == RetryPolicy.RetryDecision.Type.IGNORE)
metrics().getErrorMetrics().getIgnoresOnOtherErrors().inc();
}
}
return decision;
}
private void processRetryDecision(RetryPolicy.RetryDecision retryDecision, Connection connection, Exception exceptionToReport, boolean fromServer) {
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:
setException(connection, exceptionToReport, fromServer);
break;
case IGNORE:
if (metricsEnabled())
metrics().getErrorMetrics().getIgnores().inc();
setResult(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))
sendRequest();
}
private Connection.ResponseCallback prepareAndRetry(final String toPrepare) {
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 MultiResponseRequestHandler.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 setResult propagate the exception
setResult(connection, response);
break;
}
}
@Override
public void onException(Connection connection, Exception exception, long latency, int retryCount) {
MultiResponseRequestHandler.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 (!gotFirstResult && (!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;
}
try {
release(connection);
if (!gotFirstResult && (exception instanceof ConnectionException)) {
RetryPolicy.RetryDecision decision = computeRetryDecisionOnRequestError((ConnectionException) exception);
processRetryDecision(decision, connection, exception,
// In practice, onException is never called in response to a server error:
false);
} else {
setException(connection, exception, false);
}
} catch (Exception e) {
// This shouldn't happen, but if it does, we want to signal the callback, not let it hang indefinitely
setException(connection, new DriverInternalError("An unexpected error happened while handling exception " + exception, e), false);
}
}
@Override
public boolean onTimeout(Connection connection, long latency, int retryCount) {
// timeout can only happen for the first page so don't check gotFirstResult
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;
}
try {
// Never release the connection/handler on timeouts: the server might still send multiple responses after
// the timeout. If we cancel the handler now, Connection.Dispatcher.channelRead0 will release the streamId
// on the next response, and subsequent responses could corrupt other queries if the streamId is reused.
OperationTimedOutException timeoutException = new OperationTimedOutException(connection.address, "Timed out waiting for server response");
RetryPolicy.RetryDecision decision = computeRetryDecisionOnRequestError(timeoutException);
processRetryDecision(decision, connection, timeoutException, false);
} catch (Exception e) {
// This shouldn't happen, but if it does, we want to signal the callback, not let it hang indefinitely
setException(connection, new DriverInternalError("An unexpected error happened while handling timeout", e), false);
}
return true;
}
@Override
public int retryCount() {
return queryStateRef.get().retryCount;
}
private void setResult(Connection connection, Message.Response response) {
gotFirstResult = true;
logger.trace("[{}] Setting result", id);
try {
// Execution info describes the initial request, we will return the same object for all responses so cache
// it
if (info == null) {
info = current.defaultExecutionInfo;
if (triedHosts != null) {
triedHosts.add(current);
info = new ExecutionInfo(triedHosts);
}
if (retryConsistencyLevel != null)
info = info.withAchievedConsistency(retryConsistencyLevel);
if (response.getCustomPayload() != null)
info = info.withIncomingPayload(response.getCustomPayload());
}
callback.onResponse(connection, response, info, statement);
} catch (Exception e) {
callback.onException(connection, new DriverInternalError(
"Unexpected exception while setting final result from " + response, e), false);
}
}
private void setException(Connection connection, Exception exception, boolean fromServer) {
logger.trace("[{}] Setting exception", id);
callback.onException(connection, exception, fromServer);
}
private void logError(InetSocketAddress address, Throwable exception) {
logger.debug("[{}] Error querying {} : {}", id, address, exception.toString());
if (errors == null) {
synchronized (this) {
if (errors == null) {
errors = new ConcurrentHashMap();
}
}
}
errors.put(address, exception);
}
private void reportNoMoreHosts() {
setException(null, new NoHostAvailableException(
errors == null ? Collections.emptyMap() : errors), false);
}
interface Callback {
void register(MultiResponseRequestHandler handler);
Request getRequest();
Request getCancelRequest(int streamId);
void onResponse(Connection connection, Message.Response response, ExecutionInfo info, Statement statement);
void onException(Connection connection, Exception exception, boolean fromServer);
}
}