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

Question

当我启动我的程序时，我运行 ElasticSearch 服务并检查索引是否存在以及是否有任何文档，假设我只是运行 ES 服务并且我有这两个功能：

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);
    }
}

在 checkElasticsearchIndex 函数内部，

1. 计数操作失败并显示以下错误消息：

   OriginalException：Elasticsearch.Net.ElasticsearchClientException：远程服务器返回错误：（503）服务器不可用。调用：状态码 503 来自：GET /myindex/_count。 ServerError：类型：search_phase_execution_exception 原因：“所有分片失败”---> System.Net.WebException：远程服务器返回错误：（503）服务器不可用。

2. Health 也失败了：

   OriginalException：Elasticsearch.Net.ElasticsearchClientException：无法连接到远程服务器。调用：状态码未知来自：GET /_cluster/health/myindex?wait_for_status=yellow ---> System.Net.WebException：无法连接到远程服务器 ---> System.Net.Sockets.SocketException：无法连接是因为目标机器主动拒绝了它 127.0.0.1:9200

如您所见，我尝试了 Cluster WaitForStatus，但没有成功。

我的问题：有什么方法可以等到客户端/集群/节点准备好而不出现任何异常？

Answer 1

听起来您在启动程序的同时启动了 Elasticsearch 进程，但 Elasticsearch 需要比您的程序更长的时间才能准备好。

如果是这种情况，您可能有兴趣使用 .NET 客户端用于针对 Elasticsearch 进行集成测试的 the same abstractions。抽象从 Elasticsearch 进程读取输出以了解它何时准备就绪，并阻塞直到发生这种情况。他们是available on an AppVeyor CI package feed（计划在未来将它们发布到 Nuget）。

有some examples of how to spin up a cluster with the abstractions。对于单个节点，它将类似于

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
            }
        }
    }
}

这假设 Elasticsearch 7.5.1 zip 已经下载，并且存在于 %LOCALAPPDATA%\ElasticManaged\7.5.1\elasticsearch-7.5.1。还有更复杂的examples of how to integrate this into tests with xUnit.

您可以use the EphemeralCluster components下载、配置和运行Elasticsearch

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);
}