Elastic.Transport

Transport classes and utilities shared among .NET Elastic client libraries. Provides cluster-aware, resilient HTTP transport optimized for the Elastic product suite and Elastic Cloud.

Installation

dotnet add package Elastic.Transport

Quick Start

var settings = new TransportConfiguration(new Uri("http://localhost:9200"));
var transport = new DistributedTransport(settings);

// GET request — returns body as string
var response = transport.Get<StringResponse>("/my-index/_search?q=title:hello");

// POST request — send JSON body
var body = PostData.String(@"{ ""query"": { ""match_all"": {} } }");
var searchResponse = transport.Post<StringResponse>("/my-index/_search", body);

// HEAD request — no body needed
var headResponse = transport.Head("/my-index");

// JSON DOM with safe path traversal
var jsonResponse = transport.Get<JsonResponse>("/my-index/_search?q=title:hello");
int totalHits = jsonResponse.Get<int>("hits.total.value");
string firstId = jsonResponse.Get<string>("hits.hits.[0]._id");

// Async variants
var asyncResponse = await transport.GetAsync<StringResponse>("/my-index/_search?q=title:hello");

Response Types

The generic type parameter on Get<TResponse>, Post<TResponse>, etc. controls how the response body is read:

JsonResponse

JsonResponse deserializes JSON into a System.Text.Json.Nodes.JsonNode and exposes a Get<T>() method for safe, typed path traversal using dot-separated keys:

var response = transport.Get<JsonResponse>("/my-index/_search?q=title:hello");

// Traverse nested JSON with dot notation
int totalHits = response.Get<int>("hits.total.value");
string firstId = response.Get<string>("hits.hits.[0]._id");

// Bracket syntax for array access
string lastId = response.Get<string>("hits.hits.[last()]._id");
string firstSource = response.Get<string>("hits.hits.[first()]._source.title");

// _arbitrary_key_ traverses into the first key at that level
string fieldType = response.Get<string>("my-index.mappings.properties._arbitrary_key_.type");

// Direct DOM access is also available via .Body
JsonNode hitsNode = response.Body["hits"]["hits"];

Configuration

Single node

var settings = new TransportConfiguration(new Uri("http://localhost:9200"));

Elastic Cloud (cloud ID)

var settings = new TransportConfiguration("my-cloud-id", new ApiKey("base64key"));
// or
var settings = new TransportConfiguration("my-cloud-id", new BasicAuthentication("user", "pass"));

Multiple nodes with a node pool

var pool = new StaticNodePool(new[]
{
    new Node(new Uri("http://node1:9200")),
    new Node(new Uri("http://node2:9200")),
    new Node(new Uri("http://node3:9200"))
});
var settings = new TransportConfiguration(pool);
var transport = new DistributedTransport(settings);

All components

var pool = new StaticNodePool(new[] { new Node(new Uri("http://localhost:9200")) });
var requestInvoker = new HttpRequestInvoker();
var product = ElasticsearchProductRegistration.Default;

var settings = new TransportConfiguration(pool, requestInvoker, productRegistration: product);
var transport = new DistributedTransport(settings);

Request Pipeline

The transport models a request pipeline that handles node failover, sniffing, and pinging:

The pipeline introduces two special API calls:

• Sniff — queries the cluster to discover the current node topology
• Ping — the fastest possible request to check if a node is alive

The transport fails over in constant time. If a node is marked dead, it is skipped immediately (as long as the overall request timeout allows).

Components

Observability

Every response inherits from TransportResponse and exposes an ApiCallDetails property:

var response = transport.Get<StringResponse>("/");

// Structured call metadata
ApiCallDetails details = response.ApiCallDetails;
Console.WriteLine(details.HttpStatusCode);
Console.WriteLine(details.Uri);

// Human-readable debug string
Console.WriteLine(details.DebugInformation);

The transport also emits DiagnosticSource events for serialization timing, time-to-first-byte, and other counters.

Custom Typed Responses

Any class inheriting from TransportResponse can be used as a response type. The transport will deserialize the response body into it using System.Text.Json:

public class SearchResult : TransportResponse
{
    [JsonPropertyName("hits")]
    public HitsContainer Hits { get; set; }
}

public class HitsContainer
{
    [JsonPropertyName("total")]
    public TotalHits Total { get; set; }

    [JsonPropertyName("hits")]
    public List<Hit> Hits { get; set; }
}

public class TotalHits
{
    [JsonPropertyName("value")]
    public long Value { get; set; }
}

public class Hit
{
    [JsonPropertyName("_id")]
    public string Id { get; set; }

    [JsonPropertyName("_source")]
    public JsonNode Source { get; set; }
}

// Use it directly as a type parameter
var response = transport.Get<SearchResult>("/my-index/_search?q=title:hello");
long total = response.Hits.Total.Value;

For full control over how a response is built from the stream, implement TypedResponseBuilder<TResponse> and register it via ResponseBuilders on the configuration:

public class CsvResponse : TransportResponse
{
    public List<string[]> Rows { get; set; }
}

public class CsvResponseBuilder : TypedResponseBuilder<CsvResponse>
{
    protected override CsvResponse Build(ApiCallDetails apiCallDetails, BoundConfiguration boundConfiguration,
        Stream responseStream, string contentType, long contentLength)
    {
        using var reader = new StreamReader(responseStream);
        var rows = new List<string[]>();
        while (reader.ReadLine() is { } line)
            rows.Add(line.Split(','));
        return new CsvResponse { Rows = rows };
    }

    protected override async Task<CsvResponse> BuildAsync(ApiCallDetails apiCallDetails, BoundConfiguration boundConfiguration,
        Stream responseStream, string contentType, long contentLength, CancellationToken cancellationToken = default)
    {
        using var reader = new StreamReader(responseStream);
        var rows = new List<string[]>();
        while (await reader.ReadLineAsync(cancellationToken) is { } line)
            rows.Add(line.Split(','));
        return new CsvResponse { Rows = rows };
    }
}

var settings = new TransportConfiguration(new Uri("http://localhost:9200"))
{
    ResponseBuilders = [new CsvResponseBuilder()]
};

AOT and Source Generators

The default serializer uses System.Text.Json with a JsonSerializerContext for AOT compatibility. When using custom typed responses in AOT/trimmed applications, provide a JsonSerializerContext that includes your response types:

[JsonSerializable(typeof(SearchResult))]
[JsonSerializable(typeof(HitsContainer))]
[JsonSerializable(typeof(TotalHits))]
[JsonSerializable(typeof(Hit))]
public partial class MySerializerContext : JsonSerializerContext;

Create a concrete serializer that combines your context with the transport's built-in resolvers:

public class MySerializer : SystemTextJsonSerializer
{
    public MySerializer() : base(new TransportSerializerOptionsProvider([], null, options =>
    {
        options.TypeInfoResolver = JsonTypeInfoResolver.Combine(
            MySerializerContext.Default,
            new DefaultJsonTypeInfoResolver()
        );
    })) { }
}

var settings = new TransportConfiguration(
    new SingleNodePool(new Uri("http://localhost:9200")),
    serializer: new MySerializer()
);

Links

• GitHub Repository
• Issues
• License (Apache 2.0)