/*
* Copyright (C) 2012-2014 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 java.nio.ByteBuffer;
import java.util.*;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.LinkedBlockingDeque;
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 com.datastax.driver.core.exceptions.DriverInternalError;
/**
* 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<List<ByteBuffer>> EMPTY_QUEUE = new ArrayDeque<List<ByteBuffer>>(0);
protected final ColumnDefinitions metadata;
private ArrayBackedResultSet(ColumnDefinitions metadata) {
this.metadata = metadata;
}
static ArrayBackedResultSet fromMessage(Responses.Result msg, SessionManager session, ExecutionInfo info, Statement statement) {
info = update(info, msg, session);
switch (msg.kind) {
case VOID:
return empty(info);
case ROWS:
Responses.Result.Rows r = (Responses.Result.Rows)msg;
ColumnDefinitions columnDefs;
if (r.metadata.columns == null) {
assert statement instanceof BoundStatement;
columnDefs = ((BoundStatement)statement).statement.getPreparedId().resultSetMetadata;
assert columnDefs != null;
} else {
columnDefs = r.metadata.columns;
}
// info can be null only for internal calls, but we don't page those. We assert
// this explicitly because MultiPage implementation don't support info == null.
assert r.metadata.pagingState == null || info != null;
return r.metadata.pagingState == null
? new SinglePage(columnDefs, r.data, info)
: new MultiPage(columnDefs, r.data, info, r.metadata.pagingState, session, statement);
case SET_KEYSPACE:
case SCHEMA_CHANGE:
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);
return empty(info);
}
}
private static ExecutionInfo update(ExecutionInfo info, Responses.Result msg, SessionManager session) {
UUID tracingId = msg.getTracingId();
return tracingId == null || info == null ? info : info.withTrace(new QueryTrace(tracingId, session));
}
private static ArrayBackedResultSet empty(ExecutionInfo info) {
return new SinglePage(ColumnDefinitions.EMPTY, EMPTY_QUEUE, info);
}
public ColumnDefinitions getColumnDefinitions() {
return metadata;
}
public List<Row> 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<Row> result = new ArrayList<Row>(getAvailableWithoutFetching());
for (Row row : this)
result.add(row);
return result;
}
@Override
public Iterator<Row> iterator() {
return new Iterator<Row>() {
@Override
public boolean hasNext() {
return !isExhausted();
}
@Override
public Row next() {
return ArrayBackedResultSet.this.one();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@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<List<ByteBuffer>> rows;
private final ExecutionInfo info;
private SinglePage(ColumnDefinitions metadata,
Queue<List<ByteBuffer>> rows,
ExecutionInfo info) {
super(metadata);
this.info = info;
this.rows = rows;
}
public boolean isExhausted() {
return rows.isEmpty();
}
public Row one() {
return ArrayBackedRow.fromData(metadata, rows.poll());
}
public int getAvailableWithoutFetching() {
return rows.size();
}
public boolean isFullyFetched() {
return true;
}
public ListenableFuture<Void> fetchMoreResults() {
return Futures.immediateFuture(null);
}
public ExecutionInfo getExecutionInfo() {
return info;
}
public List<ExecutionInfo> getAllExecutionInfo() {
return Collections.singletonList(info);
}
}
private static class MultiPage extends ArrayBackedResultSet {
private Queue<List<ByteBuffer>> currentPage;
private final Queue<Queue<List<ByteBuffer>>> nextPages = new ConcurrentLinkedQueue<Queue<List<ByteBuffer>>>();
private final Deque<ExecutionInfo> infos = new LinkedBlockingDeque<ExecutionInfo>();
/*
* 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 final Statement statement;
private MultiPage(ColumnDefinitions metadata,
Queue<List<ByteBuffer>> rows,
ExecutionInfo info,
ByteBuffer pagingState,
SessionManager session,
Statement statement) {
super(metadata);
this.currentPage = rows;
this.infos.offer(info);
this.fetchState = new FetchingState(pagingState, null);
this.session = session;
this.statement = statement;
}
public boolean isExhausted() {
prepareNextRow();
return currentPage.isEmpty();
}
public Row one() {
prepareNextRow();
return ArrayBackedRow.fromData(metadata, currentPage.poll());
}
public int getAvailableWithoutFetching() {
int available = currentPage.size();
for (Queue<List<ByteBuffer>> page : nextPages)
available += page.size();
return available;
}
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;
Queue<List<ByteBuffer>> nextPage = nextPages.poll();
if (nextPage != null) {
currentPage = nextPage;
continue;
}
if (fetchingState == null)
return;
// We need to know if there is more result, so fetch the next page and
// wait on it.
try {
Uninterruptibles.getUninterruptibly(fetchMoreResults());
} catch (ExecutionException e) {
throw DefaultResultSetFuture.extractCauseFromExecutionException(e);
}
}
}
public ListenableFuture<Void> fetchMoreResults() {
return fetchMoreResults(this.fetchState);
}
private ListenableFuture<Void> fetchMoreResults(FetchingState fetchState) {
if (fetchState == null)
return Futures.immediateFuture(null);
if (fetchState.inProgress != null)
return fetchState.inProgress;
assert fetchState.nextStart != null;
ByteBuffer state = fetchState.nextStart;
SettableFuture<Void> future = SettableFuture.create();
this.fetchState = new FetchingState(null, future);
return queryNextPage(state, future);
}
private ListenableFuture<Void> queryNextPage(ByteBuffer nextStart, final SettableFuture<Void> future) {
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;
info = update(info, rm, MultiPage.this.session);
if (rm.kind == Responses.Result.Kind.ROWS) {
Responses.Result.Rows rows = (Responses.Result.Rows)rm;
MultiPage.this.nextPages.offer(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
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(null);
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) {
onSet(connection, response, null, null, latency);
}
@Override
public void onException(Connection connection, Exception exception, long latency) {
future.setException(exception);
}
@Override
public void onTimeout(Connection connection, long latency) {
// This won't be called directly since this will be wrapped by RequestHandler.
throw new UnsupportedOperationException();
}
}, statement);
return future;
}
public ExecutionInfo getExecutionInfo() {
return infos.getLast();
}
public List<ExecutionInfo> getAllExecutionInfo() {
return new ArrayList<ExecutionInfo>(infos);
}
private static class FetchingState {
public final ByteBuffer nextStart;
public final ListenableFuture<Void> inProgress;
FetchingState(ByteBuffer nextStart, ListenableFuture<Void> inProgress) {
assert (nextStart == null) != (inProgress == null);
this.nextStart = nextStart;
this.inProgress = inProgress;
}
}
}
}