elasticsearch数据信息索引操作action support示例分析

@Override
    protected void doExecute(CountRequest request, ActionListener<CountResponse> listener) {
        request.nowInMillis = System.currentTimeMillis();
        super.doExecute(request, listener);
    }

@Override
    protected void doExecute(Request request, ActionListener<Response> listener) {
        new AsyncBroadcastAction(request, listener).start();
    }

public void start() {
　　　　　　//没有shards
            if (shardsIts.size() == 0) {
                // no shards
                try {
                    listener.onResponse(newResponse(request, new AtomicReferenceArray(0), clusterState));
                } catch (Throwable e) {
                    listener.onFailure(e);
                }
                return;
            }
            request.beforeStart();
            // count the local operations, and perform the non local ones
            int shardIndex = -1;
　　　　　　　//遍历对每个shards进行操作
            for (final ShardIterator shardIt : shardsIts) {
                shardIndex++;
                final ShardRouting shard = shardIt.nextOrNull();
                if (shard != null) {
                    performOperation(shardIt, shard, shardIndex);
                } else {
                    // really, no shards active in this group
                    onOperation(null, shardIt, shardIndex, new NoShardAvailableActionException(shardIt.shardId()));
                }
            }
        }

protected void performOperation(final ShardIterator shardIt, final ShardRouting shard, final int shardIndex) {
            if (shard == null) {//shard 为null抛出异常
                // no more active shards... (we should not really get here, just safety)
                onOperation(null, shardIt, shardIndex, new NoShardAvailableActionException(shardIt.shardId()));
            } else {
                try {
                    final ShardRequest shardRequest = newShardRequest(shardIt.size(), shard, request);
                    if (shard.currentNodeId().equals(nodes.localNodeId())) {//shard在本地执行shardOperation方法，并通过onOperation方法封装结果
                        threadPool.executor(executor).execute(new Runnable() {
                            @Override
                            public void run() {
                                try {
                                    onOperation(shard, shardIndex, shardOperation(shardRequest));
                                } catch (Throwable e) {
                                    onOperation(shard, shardIt, shardIndex, e);
                                }
                            }
                        });
                    } else {//不是本地shard，发送到对应节点。
                        DiscoveryNode node = nodes.get(shard.currentNodeId());
                        if (node == null) {
                            // no node connected, act as failure
                            onOperation(shard, shardIt, shardIndex, new NoShardAvailableActionException(shardIt.shardId()));
                        } else {
                            transportService.sendRequest(node, transportShardAction, shardRequest, new BaseTransportResponseHandler<ShardResponse>() {
                                @Override
                                public ShardResponse newInstance() {
                                    return newShardResponse();
                                }
                                @Override
                                public String executor() {
                                    return ThreadPool.Names.SAME;
                                }
                                @Override
                                public void handleResponse(ShardResponse response) {
                                    onOperation(shard, shardIndex, response);
                                }
                                @Override
                                public void handleException(TransportException e) {
                                    onOperation(shard, shardIt, shardIndex, e);
                                }
                            });
                        }
                    }
                } catch (Throwable e) {
                    onOperation(shard, shardIt, shardIndex, e);
                }
            }
        }

@Override
    protected ShardCountResponse shardOperation(ShardCountRequest request) throws elasticsearchException {
        IndexService indexService = indicesService.indexServiceSafe(request.shardId().getIndex());//
        IndexShard indexShard = indexService.shardSafe(request.shardId().id());
　　　　//构造查询context
        SearchShardTarget shardTarget = new SearchShardTarget(clusterService.localNode().id(), request.shardId().getIndex(), request.shardId().id());
        SearchContext context = new DefaultSearchContext(0,
                new ShardSearchLocalRequest(request.types(), request.nowInMillis(), request.filteringAliases()),
                shardTarget, indexShard.acquireSearcher("count"), indexService, indexShard,
                scriptService, cacheRecycler, pageCacheRecycler, bigArrays, threadPool.estimatedTimeInMillisCounter());
        SearchContext.setCurrent(context);
        try {
            // TODO: min score should move to be "null" as a value that is not initialized...
            if (request.minScore() != -1) {
                context.minimumScore(request.minScore());
            }
            BytesReference source = request.querySource();
            if (source != null && source.length() > 0) {
                try {
                    QueryParseContext.setTypes(request.types());
                    context.parsedQuery(indexService.queryParserService().parseQuery(source));
                } finally {
                    QueryParseContext.removeTypes();
                }
            }
            final boolean hasTerminateAfterCount = request.terminateAfter() != DEFAULT_TERMINATE_AFTER;
            boolean terminatedEarly = false;
            context.preProcess();
            try {
                long count;
                if (hasTerminateAfterCount) {//调用lucene的封装接口执行查询并返回结果
                    final Lucene.EarlyTerminatinGCollector countCollector =
                            Lucene.createCountBasedEarlyTerminatingCollector(request.terminateAfter());
                    terminatedEarly = Lucene.countWithEarlyTermination(context.searcher(), context.query(), countCollector);
                    count = countCollector.count();
                } else {
                    count = Lucene.count(context.searcher(), context.query());
                }
                return new ShardCountResponse(request.shardId(), count, terminatedEarly);
            } catch (Exception e) {
                throw new QueryPhaseExecutionException(context, "failed to execute count", e);
            }
        } finally {
            // this will also release the index searcher
            context.close();
            SearchContext.removeCurrent();
        }
    }