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* 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
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package org.elasticsearch.action.search;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.support.ActionFilters;
import org.elasticsearch.action.support.HandledTransportAction;
import org.elasticsearch.action.support.TransportAction;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.block.ClusterBlockLevel;
import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.util.concurrent.AtomicArray;
import org.elasticsearch.common.util.concurrent.EsExecutors;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.transport.TransportService;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
public class TransportMultiSearchAction extends HandledTransportAction<MultiSearchRequest, MultiSearchResponse> {
private final int availableProcessors;
private final ClusterService clusterService;
private final TransportAction<SearchRequest, SearchResponse> searchAction;
@Inject
public TransportMultiSearchAction(Settings settings, ThreadPool threadPool, TransportService transportService,
ClusterService clusterService, TransportSearchAction searchAction,
ActionFilters actionFilters, IndexNameExpressionResolver resolver) {
super(settings, MultiSearchAction.NAME, threadPool, transportService, actionFilters, resolver, MultiSearchRequest::new);
this.clusterService = clusterService;
this.searchAction = searchAction;
this.availableProcessors = EsExecutors.numberOfProcessors(settings);
}
TransportMultiSearchAction(ThreadPool threadPool, ActionFilters actionFilters, TransportService transportService,
ClusterService clusterService, TransportAction<SearchRequest, SearchResponse> searchAction,
IndexNameExpressionResolver resolver, int availableProcessors) {
super(Settings.EMPTY, MultiSearchAction.NAME, threadPool, transportService, actionFilters, resolver, MultiSearchRequest::new);
this.clusterService = clusterService;
this.searchAction = searchAction;
this.availableProcessors = availableProcessors;
}
@Override
protected void doExecute(MultiSearchRequest request, ActionListener<MultiSearchResponse> listener) {
ClusterState clusterState = clusterService.state();
clusterState.blocks().globalBlockedRaiseException(ClusterBlockLevel.READ);
int maxConcurrentSearches = request.maxConcurrentSearchRequests();
if (maxConcurrentSearches == 0) {
maxConcurrentSearches = defaultMaxConcurrentSearches(availableProcessors, clusterState);
}
Queue<SearchRequestSlot> searchRequestSlots = new ConcurrentLinkedQueue<>();
for (int i = 0; i < request.requests().size(); i++) {
SearchRequest searchRequest = request.requests().get(i);
searchRequestSlots.add(new SearchRequestSlot(searchRequest, i));
}
int numRequests = request.requests().size();
final AtomicArray<MultiSearchResponse.Item> responses = new AtomicArray<>(numRequests);
final AtomicInteger responseCounter = new AtomicInteger(numRequests);
int numConcurrentSearches = Math.min(numRequests, maxConcurrentSearches);
for (int i = 0; i < numConcurrentSearches; i++) {
executeSearch(searchRequestSlots, responses, responseCounter, listener);
}
}
/*
* This is not perfect and makes a big assumption, that all nodes have the same thread pool size / have the number of processors and
* that shard of the indices the search requests go to are more or less evenly distributed across all nodes in the cluster. But I think
* it is a good enough default for most cases, if not then the default should be overwritten in the request itself.
*/
static int defaultMaxConcurrentSearches(int availableProcessors, ClusterState state) {
int numDateNodes = state.getNodes().getDataNodes().size();
// availableProcessors will never be larger than 32, so max defaultMaxConcurrentSearches will never be larger than 49,
// but we don't know about about other search requests that are being executed so lets cap at 10 per node
int defaultSearchThreadPoolSize = Math.min(ThreadPool.searchThreadPoolSize(availableProcessors), 10);
return Math.max(1, numDateNodes * defaultSearchThreadPoolSize);
}
/**
* Executes a single request from the queue of requests. When a request finishes, another request is taken from the queue. When a
* request is executed, a permit is taken on the specified semaphore, and released as each request completes.
*
* @param requests the queue of multi-search requests to execute
* @param responses atomic array to hold the responses corresponding to each search request slot
* @param responseCounter incremented on each response
* @param listener the listener attached to the multi-search request
*/
private void executeSearch(
final Queue<SearchRequestSlot> requests,
final AtomicArray<MultiSearchResponse.Item> responses,
final AtomicInteger responseCounter,
final ActionListener<MultiSearchResponse> listener) {
SearchRequestSlot request = requests.poll();
if (request == null) {
/*
* The number of times that we poll an item from the queue here is the minimum of the number of requests and the maximum number
* of concurrent requests. At first glance, it appears that we should never poll from the queue and not obtain a request given
* that we only poll here no more times than the number of requests. However, this is not the only consumer of this queue as
* earlier requests that have already completed will poll from the queue too and they could complete before later polls are
* invoked here. Thus, it can be the case that we poll here and and the queue was empty.
*/
return;
}
/*
* With a request in hand, we are now prepared to execute the search request. There are two possibilities, either we go asynchronous
* or we do not (this can happen if the request does not resolve to any shards). If we do not go asynchronous, we are going to come
* back on the same thread that attempted to execute the search request. At this point, or any other point where we come back on the
* same thread as when the request was submitted, we should not recurse lest we might descend into a stack overflow. To avoid this,
* when we handle the response rather than going recursive, we fork to another thread, otherwise we recurse.
*/
final Thread thread = Thread.currentThread();
searchAction.execute(request.request, new ActionListener<SearchResponse>() {
@Override
public void onResponse(final SearchResponse searchResponse) {
handleResponse(request.responseSlot, new MultiSearchResponse.Item(searchResponse, null));
}
@Override
public void onFailure(final Exception e) {
handleResponse(request.responseSlot, new MultiSearchResponse.Item(null, e));
}
private void handleResponse(final int responseSlot, final MultiSearchResponse.Item item) {
responses.set(responseSlot, item);
if (responseCounter.decrementAndGet() == 0) {
assert requests.isEmpty();
finish();
} else {
if (thread == Thread.currentThread()) {
// we are on the same thread, we need to fork to another thread to avoid recursive stack overflow on a single thread
threadPool.generic().execute(() -> executeSearch(requests, responses, responseCounter, listener));
} else {
// we are on a different thread (we went asynchronous), it's safe to recurse
executeSearch(requests, responses, responseCounter, listener);
}
}
}
private void finish() {
listener.onResponse(new MultiSearchResponse(responses.toArray(new MultiSearchResponse.Item[responses.length()])));
}
});
}
static final class SearchRequestSlot {
final SearchRequest request;
final int responseSlot;
SearchRequestSlot(SearchRequest request, int responseSlot) {
this.request = request;
this.responseSlot = responseSlot;
}
}
}