CosmosDb 首次连接可能需要很多秒

Question

我正在测试 CosmosDb。我发现初始连接通常需要很多秒。我编写了一个小型 .net core 2.2 控制台应用程序来演示该问题。

   static async System.Threading.Tasks.Task Main(string[] args)
    {
        Console.WriteLine("Hello World!");
        string url = "https://docdb.documents.azure.com:443/";
        string key = "myKey";
        DocumentClient docClient = new DocumentClient(new Uri(url), key);
        Stopwatch sw = new Stopwatch();
        while (true)
        {
            sw.Start();
            var res = await docClient.ReadDocumentAsync(UriFactory.CreateDocumentUri("ct", "ops", "xxx"),
                new RequestOptions { PartitionKey = new Microsoft.Azure.Documents.PartitionKey("test") });
            sw.Stop();
            Console.WriteLine($"Query took {sw.ElapsedMilliseconds}ms");
            sw.Reset();
           await Task.Delay(1000);
        }
    }

这是我的典型结果：

Hello World!
Query took 48530ms
Query took 36ms
Query took 26ms
Query took 15ms

第一个请求需要 48 秒！我尝试将 docClient 构造修改为：

 DocumentClient docClient = new DocumentClient(new Uri(url), key,new 
 ConnectionPolicy {ConnectionMode = ConnectionMode.Direct,ConnectionProtocol 
 = Protocol.Tcp });

要查看是否更好一些典型结果：

 Hello World!
Query took 20536ms
Query took 104ms
Query took 37ms
Query took 71ms
Query took 13ms
Query took 88ms
Query took 14ms

第一次查询还有 20 秒。

我的数据库是

130Mb     
Avg Throughput /s*  3.58 RU/s

我有

 400 RU's 

有什么办法可以减轻第一次连接的延迟吗？

我关于 Cosmosdb 的文档是：

 {
"id": "xxx",
"fid": "test",
"_rid": "VX8TAPKGDqNeWwEAAAAAAA==",
"_self": "dbs/VX8TAA==/colls/VX8TAPKGDqM=/docs/VX8TAPKGDqNeWwEAAAAAAA==/",
"_etag": "\"0000d4a2-0000-1100-0000-5ce801ef0000\"",
"_attachments": "attachments/",
"_ts": 1558708719
}

Answer 1

这是预期的，请参阅https://learn.microsoft.com/en-us/azure/cosmos-db/performance-tips#networking中的第 2 点

默认情况下，第一个请求具有较高的延迟，因为它必须获取地址路由表。为了避免在第一个请求时出现这种启动延迟，您应该在初始化期间调用 OpenAsync() 一次，如下所示。

static async System.Threading.Tasks.Task Main(string[] args)
{
    Console.WriteLine("Hello World!");
    string url = "https://docdb.documents.azure.com:443/";
    string key = "myKey";
    DocumentClient docClient = new DocumentClient(new Uri(url), key);
    await docClient.OpenAsync();
    Stopwatch sw = new Stopwatch();
    while (true)
    {
        sw.Start();
        var res = await docClient.ReadDocumentAsync(UriFactory.CreateDocumentUri("ct", "ops", "xxx"),
            new RequestOptions { PartitionKey = new Microsoft.Azure.Documents.PartitionKey("test") });
        sw.Stop();
        Console.WriteLine($"Query took {sw.ElapsedMilliseconds}ms");
        sw.Reset();
       await Task.Delay(1000);
    }
}