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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 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.datastax.driver.core.exceptions.ConnectionException;
import com.datastax.driver.core.exceptions.DriverInternalError;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;
import com.google.common.util.concurrent.Uninterruptibles;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.nio.ByteBuffer;
import java.util.*;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.LinkedBlockingDeque;
/**
* Default implementation of a result set, backed by an ArrayDeque of ArrayList.
*/
abstract class ArrayBackedResultSet implements ResultSet {
private static final Logger logger = LoggerFactory.getLogger(ResultSet.class);
private static final Queue> EMPTY_QUEUE = new ArrayDeque>(0);
protected volatile ColumnDefinitions metadata;
protected final Token.Factory tokenFactory;
private final boolean wasApplied;
protected final ProtocolVersion protocolVersion;
protected final CodecRegistry codecRegistry;
private ArrayBackedResultSet(ColumnDefinitions metadata, Token.Factory tokenFactory, List firstRow, ProtocolVersion protocolVersion, CodecRegistry codecRegistry) {
this.metadata = metadata;
this.protocolVersion = protocolVersion;
this.codecRegistry = codecRegistry;
this.tokenFactory = tokenFactory;
this.wasApplied = checkWasApplied(firstRow, metadata, protocolVersion);
}
static ArrayBackedResultSet fromMessage(Responses.Result msg, SessionManager session, ProtocolVersion protocolVersion, ExecutionInfo info, Statement statement) {
switch (msg.kind) {
case ROWS:
Responses.Result.Rows r = (Responses.Result.Rows) msg;
Statement actualStatement = statement;
if (statement instanceof StatementWrapper) {
actualStatement = ((StatementWrapper) statement).getWrappedStatement();
}
ColumnDefinitions columnDefs = r.metadata.columns;
if (columnDefs == null) {
// If result set metadata is not present, it means the request had SKIP_METADATA set, the driver
// only ever does that for bound statements.
BoundStatement bs = (BoundStatement) actualStatement;
columnDefs = bs.preparedStatement().getPreparedId().resultSetMetadata.variables;
} else {
// Otherwise, always use the response's metadata.
// In addition, if a new id is present it means we're executing a bound statement with protocol v5,
// the schema changed server-side, and we need to update the prepared statement (see
// CASSANDRA-10786).
MD5Digest newMetadataId = r.metadata.metadataId;
assert !(actualStatement instanceof BoundStatement) ||
ProtocolFeature.PREPARED_METADATA_CHANGES.isSupportedBy(protocolVersion) ||
newMetadataId == null;
if (newMetadataId != null) {
BoundStatement bs = ((BoundStatement) actualStatement);
PreparedId preparedId = bs.preparedStatement().getPreparedId();
preparedId.resultSetMetadata = new PreparedId.PreparedMetadata(newMetadataId, columnDefs);
}
}
assert columnDefs != null;
Token.Factory tokenFactory = (session == null) ? null
: session.getCluster().manager.metadata.tokenFactory();
info = update(info, r, session, r.metadata.pagingState, protocolVersion, columnDefs.codecRegistry, statement);
// info can be null only for internal calls, but we don't page those. We assert
// this explicitly because MultiPage implementation doesn't support info == null.
assert r.metadata.pagingState == null || info != null;
return r.metadata.pagingState == null
? new SinglePage(columnDefs, tokenFactory, protocolVersion, columnDefs.codecRegistry, r.data, info)
: new MultiPage(columnDefs, tokenFactory, protocolVersion, columnDefs.codecRegistry, r.data, info, r.metadata.pagingState, session);
case VOID:
case SET_KEYSPACE:
case SCHEMA_CHANGE:
info = update(info, msg, session, null, protocolVersion, null, statement);
return empty(info);
case PREPARED:
throw new RuntimeException("Prepared statement received when a ResultSet was expected");
default:
logger.error("Received unknown result type '{}'; returning empty result set", msg.kind);
info = update(info, msg, session, null, protocolVersion, null, statement);
return empty(info);
}
}
private static ExecutionInfo update(ExecutionInfo info, Responses.Result msg, SessionManager session,
ByteBuffer pagingState, ProtocolVersion protocolVersion, CodecRegistry codecRegistry,
Statement statement) {
if (info == null)
return null;
UUID tracingId = msg.getTracingId();
QueryTrace trace = (tracingId == null) ? null : new QueryTrace(tracingId, session);
return info.with(trace, msg.warnings, pagingState, statement, protocolVersion, codecRegistry);
}
private static ArrayBackedResultSet empty(ExecutionInfo info) {
// We could pass the protocol version but we know we won't need it so passing a bogus value (null)
return new SinglePage(ColumnDefinitions.EMPTY, null, null, null, EMPTY_QUEUE, info);
}
@Override
public ColumnDefinitions getColumnDefinitions() {
return metadata;
}
@Override
public List all() {
if (isExhausted())
return Collections.emptyList();
// We may have more than 'getAvailableWithoutFetching' results but we won't have less, and
// at least in the single page case this will be exactly the size we want so ...
List result = new ArrayList(getAvailableWithoutFetching());
for (Row row : this)
result.add(row);
return result;
}
@Override
public Iterator iterator() {
return new Iterator() {
@Override
public boolean hasNext() {
return !isExhausted();
}
@Override
public Row next() {
return ArrayBackedResultSet.this.one();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@Override
public boolean wasApplied() {
return wasApplied;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("ResultSet[ exhausted: ").append(isExhausted());
sb.append(", ").append(metadata).append(']');
return sb.toString();
}
private static class SinglePage extends ArrayBackedResultSet {
private final Queue> rows;
private final ExecutionInfo info;
private SinglePage(ColumnDefinitions metadata,
Token.Factory tokenFactory,
ProtocolVersion protocolVersion,
CodecRegistry codecRegistry,
Queue> rows,
ExecutionInfo info) {
super(metadata, tokenFactory, rows.peek(), protocolVersion, codecRegistry);
this.info = info;
this.rows = rows;
}
@Override
public boolean isExhausted() {
return rows.isEmpty();
}
@Override
public Row one() {
return ArrayBackedRow.fromData(metadata, tokenFactory, protocolVersion, rows.poll());
}
@Override
public int getAvailableWithoutFetching() {
return rows.size();
}
@Override
public boolean isFullyFetched() {
return true;
}
@Override
public ListenableFuture fetchMoreResults() {
return Futures.immediateFuture(this);
}
@Override
public ExecutionInfo getExecutionInfo() {
return info;
}
@Override
public List getAllExecutionInfo() {
return Collections.singletonList(info);
}
}
private static class MultiPage extends ArrayBackedResultSet {
private Queue> currentPage;
private final Queue nextPages = new ConcurrentLinkedQueue();
private final Deque infos = new LinkedBlockingDeque();
/*
* The fetching state of this result set. The fetchState will always be in one of
* the 3 following state:
* 1) fetchState is null or reference a null: fetching is done, there
* is nothing more to fetch and no query in progress.
* 2) fetchState.get().nextStart is not null: there is more pages to fetch. In
* that case, inProgress is *guaranteed* to be null.
* 3) fetchState.get().inProgress is not null: a page is being fetched.
* In that case, nextStart is *guaranteed* to be null.
*
* Also note that while ResultSet doesn't pretend to be thread-safe, the actual
* fetch is done asynchronously and so we do need to be volatile below.
*/
private volatile FetchingState fetchState;
private final SessionManager session;
private MultiPage(ColumnDefinitions metadata,
Token.Factory tokenFactory,
ProtocolVersion protocolVersion,
CodecRegistry codecRegistry,
Queue> rows,
ExecutionInfo info,
ByteBuffer pagingState,
SessionManager session) {
// Note: as of Cassandra 2.1.0, it turns out that the result of a CAS update is never paged, so
// we could hard-code the result of wasApplied in this class to "true". However, we can not be sure
// that this will never change, so apply the generic check by peeking at the first row.
super(metadata, tokenFactory, rows.peek(), protocolVersion, codecRegistry);
this.currentPage = rows;
this.infos.offer(info);
this.fetchState = new FetchingState(pagingState, null);
this.session = session;
}
@Override
public boolean isExhausted() {
prepareNextRow();
return currentPage.isEmpty();
}
@Override
public Row one() {
prepareNextRow();
return ArrayBackedRow.fromData(metadata, tokenFactory, protocolVersion, currentPage.poll());
}
@Override
public int getAvailableWithoutFetching() {
int available = currentPage.size();
for (NextPage page : nextPages)
available += page.data.size();
return available;
}
@Override
public boolean isFullyFetched() {
return fetchState == null;
}
// Ensure that after the call the next row to consume is in 'currentPage', i.e. that
// 'currentPage' is empty IFF the ResultSet if fully exhausted.
private void prepareNextRow() {
while (currentPage.isEmpty()) {
// Grab the current state now to get a consistent view in this iteration.
FetchingState fetchingState = this.fetchState;
NextPage nextPage = nextPages.poll();
if (nextPage != null) {
if (nextPage.metadata != null) {
this.metadata = nextPage.metadata;
}
currentPage = nextPage.data;
continue;
}
if (fetchingState == null)
return;
// We need to know if there is more result, so fetch the next page and
// wait on it.
try {
session.checkNotInEventLoop();
Uninterruptibles.getUninterruptibly(fetchMoreResults());
} catch (ExecutionException e) {
throw DriverThrowables.propagateCause(e);
}
}
}
@Override
public ListenableFuture fetchMoreResults() {
return fetchMoreResults(this.fetchState);
}
private ListenableFuture fetchMoreResults(FetchingState fetchState) {
if (fetchState == null)
return Futures.immediateFuture(this);
if (fetchState.inProgress != null)
return fetchState.inProgress;
assert fetchState.nextStart != null;
ByteBuffer state = fetchState.nextStart;
SettableFuture future = SettableFuture.create();
this.fetchState = new FetchingState(null, future);
return queryNextPage(state, future);
}
private ListenableFuture queryNextPage(ByteBuffer nextStart, final SettableFuture future) {
Statement statement = this.infos.peek().getStatement();
assert !(statement instanceof BatchStatement);
final Message.Request request = session.makeRequestMessage(statement, nextStart);
session.execute(new RequestHandler.Callback() {
@Override
public Message.Request request() {
return request;
}
@Override
public void register(RequestHandler handler) {
}
@Override
public void onSet(Connection connection, Message.Response response, ExecutionInfo info, Statement statement, long latency) {
try {
switch (response.type) {
case RESULT:
Responses.Result rm = (Responses.Result) response;
if (rm.kind == Responses.Result.Kind.ROWS) {
Responses.Result.Rows rows = (Responses.Result.Rows) rm;
info = update(info, rm, MultiPage.this.session, rows.metadata.pagingState, protocolVersion, codecRegistry, statement);
// If the query is a prepared 'SELECT *', the metadata can change between pages
ColumnDefinitions newMetadata = null;
if (rows.metadata.metadataId != null) {
newMetadata = rows.metadata.columns;
assert statement instanceof BoundStatement;
BoundStatement bs = (BoundStatement) statement;
bs.preparedStatement().getPreparedId().resultSetMetadata =
new PreparedId.PreparedMetadata(rows.metadata.metadataId, rows.metadata.columns);
}
MultiPage.this.nextPages.offer(new NextPage(newMetadata, rows.data));
MultiPage.this.fetchState = rows.metadata.pagingState == null ? null : new FetchingState(rows.metadata.pagingState, null);
} else if (rm.kind == Responses.Result.Kind.VOID) {
// We shouldn't really get a VOID message here but well, no harm in handling it I suppose
info = update(info, rm, MultiPage.this.session, null, protocolVersion, codecRegistry, statement);
MultiPage.this.fetchState = null;
} else {
logger.error("Received unknown result type '{}' during paging: ignoring message", rm.kind);
// This mean we have probably have a bad node, so defunct the connection
connection.defunct(new ConnectionException(connection.address, String.format("Got unexpected %s result response", rm.kind)));
future.setException(new DriverInternalError(String.format("Got unexpected %s result response from %s", rm.kind, connection.address)));
return;
}
MultiPage.this.infos.offer(info);
future.set(MultiPage.this);
break;
case ERROR:
future.setException(((Responses.Error) response).asException(connection.address));
break;
default:
// This mean we have probably have a bad node, so defunct the connection
connection.defunct(new ConnectionException(connection.address, String.format("Got unexpected %s response", response.type)));
future.setException(new DriverInternalError(String.format("Got unexpected %s response from %s", response.type, connection.address)));
break;
}
} catch (RuntimeException e) {
// If we get a bug here, the client will not get it, so better forwarding the error
future.setException(new DriverInternalError("Unexpected error while processing response from " + connection.address, e));
}
}
// This is only called for internal calls, so don't bother with ExecutionInfo
@Override
public void onSet(Connection connection, Message.Response response, long latency, int retryCount) {
onSet(connection, response, null, null, latency);
}
@Override
public void onException(Connection connection, Exception exception, long latency, int retryCount) {
future.setException(exception);
}
@Override
public boolean onTimeout(Connection connection, long latency, int retryCount) {
// This won't be called directly since this will be wrapped by RequestHandler.
throw new UnsupportedOperationException();
}
@Override
public int retryCount() {
// This is only called for internal calls (i.e, when the callback is not wrapped in RequestHandler).
// There is no retry logic in that case, so the value does not really matter.
return 0;
}
}, statement);
return future;
}
@Override
public ExecutionInfo getExecutionInfo() {
return infos.getLast();
}
@Override
public List getAllExecutionInfo() {
return new ArrayList(infos);
}
private static class FetchingState {
public final ByteBuffer nextStart;
public final ListenableFuture inProgress;
FetchingState(ByteBuffer nextStart, ListenableFuture inProgress) {
assert (nextStart == null) != (inProgress == null);
this.nextStart = nextStart;
this.inProgress = inProgress;
}
}
private static class NextPage {
final ColumnDefinitions metadata;
final Queue> data;
NextPage(ColumnDefinitions metadata, Queue> data) {
this.metadata = metadata;
this.data = data;
}
}
}
// This method checks the value of the "[applied]" column manually, to avoid instantiating an ArrayBackedRow
// object that we would throw away immediately.
private static boolean checkWasApplied(List firstRow, ColumnDefinitions metadata, ProtocolVersion protocolVersion) {
// If the column is not present or not a boolean, we assume the query
// was not a conditional statement, and therefore return true.
if (firstRow == null)
return true;
int[] is = metadata.findAllIdx("[applied]");
if (is == null)
return true;
int i = is[0];
if (!DataType.cboolean().equals(metadata.getType(i)))
return true;
// Otherwise return the value of the column
ByteBuffer value = firstRow.get(i);
if (value == null || value.remaining() == 0)
return false;
return TypeCodec.cboolean().deserializeNoBoxing(value, protocolVersion);
}
}