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Elastic Docs ›Elasticsearch.Net and NEST: the .NET clients [5.x] ›Troubleshooting ›Logging

Logging with OnRequestCompleted

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Logging with OnRequestCompleted

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When constructing the connection settings to pass to the client, you can pass a callback of type Action<IApiCallDetails> to the OnRequestCompleted method that can eavesdrop every time a response(good or bad) is received.

If you have complex logging needs this is a good place to add that in since you have access to both the request and response details.

In this example, we’ll use OnRequestCompleted on connection settings to increment a counter each time it’s called.

var counter = 0;
var client = new ElasticClient(new AlwaysInMemoryConnectionSettings().OnRequestCompleted(r => counter++)); 

client.RootNodeInfo(); 
counter.Should().Be(1);

await client.RootNodeInfoAsync(); 
counter.Should().Be(2);

Construct a client

Make a synchronous call and assert the counter is incremented

Make an asynchronous call and assert the counter is incremented

OnRequestCompleted is called even when an exception is thrown, so it can be used even if the client is configured to throw exceptions

var counter = 0;
var client = FixedResponseClient.Create( 
    new { },
    500,
    connectionSettings => connectionSettings
        .ThrowExceptions() 
        .OnRequestCompleted(r => counter++)
);

Assert.Throws<ElasticsearchClientException>(() => client.RootNodeInfo()); 
counter.Should().Be(1);

await Assert.ThrowsAsync<ElasticsearchClientException>(async () => await client.RootNodeInfoAsync());
counter.Should().Be(2);

Configure a client with a connection that **always returns a HTTP 500 response

Always throw exceptions when a call results in an exception

Assert an exception is thrown and the counter is incremented

Here’s an example using OnRequestCompleted() for more complex logging

By default, the client writes directly to the request stream and deserializes directly from the response stream.

If you would also like to capture the request and/or response bytes, you also need to set .DisableDirectStreaming() to true.

var list = new List<string>();
var connectionPool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));

var settings = new ConnectionSettings(connectionPool, new InMemoryConnection()) 
    .DefaultIndex("default-index")
    .DisableDirectStreaming() 
    .OnRequestCompleted(apiCallDetails => 
    {
        // log out the request and the request body, if one exists for the type of request
        if (apiCallDetails.RequestBodyInBytes != null)
        {
            list.Add(
                $"{apiCallDetails.HttpMethod} {apiCallDetails.Uri} " +
                $"{Encoding.UTF8.GetString(apiCallDetails.RequestBodyInBytes)}");
        }
        else
        {
            list.Add($"{apiCallDetails.HttpMethod} {apiCallDetails.Uri}");
        }

        // log out the response and the response body, if one exists for the type of response
        if (apiCallDetails.ResponseBodyInBytes != null)
        {
            list.Add($"Status: {apiCallDetails.HttpStatusCode}" +
                     $"{Encoding.UTF8.GetString(apiCallDetails.ResponseBodyInBytes)}");
        }
        else
        {
            list.Add($"Status: {apiCallDetails.HttpStatusCode}");
        }
    });

var client = new ElasticClient(settings);

var syncResponse = client.Search<object>(s => s 
    .AllTypes()
    .AllIndices()
    .Scroll("2m")
    .Sort(ss => ss
        .Ascending(SortSpecialField.DocumentIndexOrder)
    )
);

list.Count.Should().Be(2);

var asyncResponse = await client.SearchAsync<object>(s => s 
    .AllTypes()
    .AllIndices()
    .Scroll("10m")
    .Sort(ss => ss
        .Ascending(SortSpecialField.DocumentIndexOrder)
    )
);

list.Count.Should().Be(4);
list.Should().BeEquivalentTo(new[] 
{
    @"POST http://localhost:9200/_search?scroll=2m {""sort"":[{""_doc"":{""order"":""asc""}}]}",
    @"Status: 200",
    @"POST http://localhost:9200/_search?scroll=10m {""sort"":[{""_doc"":{""order"":""asc""}}]}",
    @"Status: 200"
});

Here we use InMemoryConnection but in a real application, you’d use an IConnection that actually sends the request, such as HttpConnection

Disable direct streaming so we can capture the request and response bytes

Perform some action when a request completes. Here, we’re just adding to a list, but in your application you may be logging to a file.

Make a synchronous call

Make an asynchronous call

Assert the list contains the contents written in the delegate passed to OnRequestCompleted

When running an application in production, you probably don’t want to disable direct streaming for all requests, since doing so will incur a performance overhead, due to buffering request and response bytes in memory. It can however be useful to capture requests and responses in an ad-hoc fashion, perhaps to troubleshoot an issue in production.

DisableDirectStreaming can be enabled on a per-request basis for this purpose. In using this feature, it is possible to configure a general logging mechanism in OnRequestCompleted and log out request and responses only when necessary

var list = new List<string>();
var connectionPool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));

var settings = new ConnectionSettings(connectionPool, new InMemoryConnection())
    .DefaultIndex("default-index")
    .OnRequestCompleted(apiCallDetails =>
    {
        // log out the request and the request body, if one exists for the type of request
        if (apiCallDetails.RequestBodyInBytes != null)
        {
            list.Add(
                $"{apiCallDetails.HttpMethod} {apiCallDetails.Uri} " +
                $"{Encoding.UTF8.GetString(apiCallDetails.RequestBodyInBytes)}");
        }
        else
        {
            list.Add($"{apiCallDetails.HttpMethod} {apiCallDetails.Uri}");
        }

        // log out the response and the response body, if one exists for the type of response
        if (apiCallDetails.ResponseBodyInBytes != null)
        {
            list.Add($"Status: {apiCallDetails.HttpStatusCode}" +
                     $"{Encoding.UTF8.GetString(apiCallDetails.ResponseBodyInBytes)}");
        }
        else
        {
            list.Add($"Status: {apiCallDetails.HttpStatusCode}");
        }
    });

var client = new ElasticClient(settings);

var syncResponse = client.Search<object>(s => s 
    .AllTypes()
    .AllIndices()
    .Scroll("2m")
    .Sort(ss => ss
        .Ascending(SortSpecialField.DocumentIndexOrder)
    )
);

list.Count.Should().Be(2);

var asyncResponse = await client.SearchAsync<object>(s => s 
    .RequestConfiguration(r => r
        .DisableDirectStreaming()
    )
    .AllTypes()
    .AllIndices()
    .Scroll("10m")
    .Sort(ss => ss
        .Ascending(SortSpecialField.DocumentIndexOrder)
    )
);

list.Count.Should().Be(4);
list.Should().BeEquivalentTo(new[]
{
    @"POST http://localhost:9200/_search?scroll=2m", 
    @"Status: 200",
    @"POST http://localhost:9200/_search?scroll=10m {""sort"":[{""_doc"":{""order"":""asc""}}]}", 
    @"Status: 200"
});

Make a synchronous call where the request and response bytes will not be buffered

Make an asynchronous call where DisableDirectStreaming() is enabled

Only the method and url for the first request is captured

the body of the second request is captured
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