Elasticsearch节点关闭

节点关闭的时机

当Elasticsearch启动时，在Bootstrap.setup()过程中有这么一段，这里注册了节点关闭执行的钩子。

if (addShutdownHook) {
            Runtime.getRuntime().addShutdownHook(new Thread() {
                @Override
                public void run() {
                    try {
                        IOUtils.close(node, spawner);
                        LoggerContext context = (LoggerContext) LogManager.getContext(false);
                        Configurator.shutdown(context);
                    } catch (IOException ex) {
                        throw new ElasticsearchException("failed to stop node", ex);
                    }
                }
            });
        }

当收到 SIGTERM 或 SIGINT信号时就会执行节点关闭流程

节点关闭进行的操作

Node.class实现了Closeable接口，当IOUtil.close(node, spawner)调用时就会调用node.close()
在node.close()中，会对guice中管理的Service进行关闭。
Elasticsearch的Service都会实现start和stop方法，方便在节点启动和关闭时进行调用。start和stop方法实际会调用各个Service自己实现的doStart()和doStop()接口来进行启动或者关闭。

由于各个Service之间可能存在依赖关系，因此在关闭的时候也应该按照顺序进行关闭，这些服务关闭的顺序与启动的时候相反

        injector.getInstance(ResourceWatcherService.class).stop();
        injector.getInstance(HttpServerTransport.class).stop();

        injector.getInstance(SnapshotsService.class).stop();
        injector.getInstance(SnapshotShardsService.class).stop();
        // stop any changes happening as a result of cluster state changes
        injector.getInstance(IndicesClusterStateService.class).stop();
        // close discovery early to not react to pings anymore.
        // This can confuse other nodes and delay things - mostly if we're the master and we're running tests.
        injector.getInstance(Discovery.class).stop();
        // we close indices first, so operations won't be allowed on it
        injector.getInstance(RoutingService.class).stop();
        injector.getInstance(ClusterService.class).stop();
        injector.getInstance(NodeConnectionsService.class).stop();
        nodeService.getMonitorService().stop();
        injector.getInstance(GatewayService.class).stop();
        injector.getInstance(SearchService.class).stop();
        injector.getInstance(TransportService.class).stop();

        pluginLifecycleComponents.forEach(LifecycleComponent::stop);
        // we should stop this last since it waits for resources to get released
        // if we had scroll searchers etc or recovery going on we wait for to finish.
        injector.getInstance(IndicesService.class).stop();