避免ElasticSearch错误503服务器不可用：使用WaitForStatus

Question

public ElasticClient getElasticSearchClient()
{
    ConnectionSettings connectionSettings = new Nest.ConnectionSettings(new Uri("http://localhost:9200"))
                                                    .DefaultIndex("myindex")
                                                    .DisableDirectStreaming();
    ElasticClient client = new ElasticClient(connectionSettings);
    //var health = client.Cluster.Health("myindex", a => (a.WaitForStatus(WaitForStatus.Yellow)).Timeout(50));
    return client;
}

public void checkElasticsearchIndex()
{
    var client = getElasticSearchClient();

    var health = this.client.Cluster.Health("myindex", a => (a.WaitForStatus(WaitForStatus.Yellow)));

    CountResponse count = client.Count<myobject>();

    if (!client.Indices.Exists("myindex").IsValid || count.Count == 0)
    {
        BulkWriteAllToIndexES(client);
    }
}

>

计数操作失败，出现以下错误消息：

OriginalException：ElasticSearch.Net.ElasticSearchClientException：远程服务器返回错误：（503）服务器不可用。调用：状态代码503来自：GET/myindex/_count。ServerError：Type：search_phase_execution_exception原因：“All shards Failed”---->System.Net.WebException：远程服务器返回错误：（503）服务器不可用。

健康状况也会下降：

我的问题：有没有办法等到客户机/集群/节点准备就绪而不得到任何例外？

Answer 1

听起来像是在启动程序的同时启动了Elasticsearch过程，但是Elasticsearch需要比程序更长的时间才能准备好。

如果是这种情况，您可能对使用.NET客户端用于针对ElasticSearch进行集成测试的相同抽象感兴趣。这些抽象从Elasticsearch进程读取输出，以了解它何时准备就绪，并阻塞直到发生为止。它们可以在AppVeyor配置项包提要上使用（计划将来将它们发布到Nuget）。

有一些例子说明了如何使用抽象来升级集群。对于单个节点，类似于

using System;
using Elastic.Managed.Configuration;
using Elastic.Managed.ConsoleWriters;
using Elastic.Managed.FileSystem;

namespace Elastic.Managed.Example
{
    class Program
    {
        static void Main(string[] args)
        {
            var version = "7.5.1";
            var esHome = Environment.ExpandEnvironmentVariables($@"%LOCALAPPDATA%\ElasticManaged\{version}\elasticsearch-{version}");

            using (var node = new ElasticsearchNode(version, esHome))
            {
                node.SubscribeLines(new LineHighlightWriter());
                if (!node.WaitForStarted(TimeSpan.FromMinutes(2))) throw new Exception();

                // do your work here
            }
        }
    }
}

var plugins = new ElasticsearchPlugins(ElasticsearchPlugin.RepositoryAzure, ElasticsearchPlugin.IngestAttachment);
var config = new EphemeralClusterConfiguration("7.5.1", ClusterFeatures.XPack, plugins, numberOfNodes: 1);
using (var cluster = new EphemeralCluster(config))
{
    cluster.Start();

    var nodes = cluster.NodesUris();
    var connectionPool = new StaticConnectionPool(nodes);
    var settings = new ConnectionSettings(connectionPool).EnableDebugMode();
    var client = new ElasticClient(settings);

    Console.Write(client.CatPlugins().DebugInformation);
}