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HTTP

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HTTP

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The HTTP layer exposes Elasticsearch’s REST APIs over HTTP.

The HTTP mechanism is completely asynchronous in nature, meaning that there is no blocking thread waiting for a response. The benefit of using asynchronous communication for HTTP is solving the C10k problem.

When possible, consider using HTTP keep alive when connecting for better performance and try to get your favorite client not to do HTTP chunking.

HTTP settings

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The following settings can be configured for HTTP. These settings also use the common network settings.

HTTP settings cannot be updated dynamically. You must configure these settings in the Elasticsearch configuration file and restart Elasticsearch for changes to take effect.

http.port: A bind port range. Defaults to 9200-9300.
http.publish_port: The port that HTTP clients should use when communicating with this node. Useful when a cluster node is behind a proxy or firewall and the http.port is not directly addressable from the outside. Defaults to the actual port assigned via http.port.
http.bind_host: The host address to bind the HTTP service to. Defaults to http.host (if set) or network.bind_host.
http.publish_host: The host address to publish for HTTP clients to connect to. Defaults to http.host (if set) or network.publish_host.
http.host: Used to set the http.bind_host and the http.publish_host.
http.max_content_length: The max content of an HTTP request. Defaults to 100MB.
http.max_initial_line_length: The max length of an HTTP URL. Defaults to 4KB.
http.max_header_size: The max size of allowed headers. Defaults to 8KB.

http.compression

Support for compression when possible (with Accept-Encoding). If HTTPS is enabled, defaults to false. Otherwise, defaults to true.

Disabling compression for HTTPS mitigates potential security risks, such as a BREACH attack. To compress HTTPS traffic, you must explicitly set http.compression to true.

http.compression_level

Defines the compression level to use for HTTP responses. Valid values are in the range of 1 (minimum compression) and 9 (maximum compression). Defaults to 3.

http.cors.enabled: Enable or disable cross-origin resource sharing, which determines whether a browser on another origin can execute requests against Elasticsearch. Set to true to enable Elasticsearch to process pre-flight CORS requests. Elasticsearch will respond to those requests with the Access-Control-Allow-Origin header if the Origin sent in the request is permitted by the http.cors.allow-origin list. Set to false (the default) to make Elasticsearch ignore the Origin request header, effectively disabling CORS requests because Elasticsearch will never respond with the Access-Control-Allow-Origin response header.

If the client does not send a pre-flight request with an Origin header or it does not check the response headers from the server to validate the Access-Control-Allow-Origin response header, then cross-origin security is compromised. If CORS is not enabled on Elasticsearch, the only way for the client to know is to send a pre-flight request and realize the required response headers are missing.

http.cors.allow-origin: Which origins to allow. If you prepend and append a forward slash (/) to the value, this will be treated as a regular expression, allowing you to support HTTP and HTTPs. For example, using /https?:\/\/localhost(:[0-9]+)?/ would return the request header appropriately in both cases. Defaults to no origins allowed.

A wildcard (*) is a valid value but is considered a security risk, as your Elasticsearch instance is open to cross origin requests from anywhere.

http.cors.max-age: Browsers send a "preflight" OPTIONS-request to determine CORS settings. max-age defines how long the result should be cached for. Defaults to 1728000 (20 days).

http.cors.allow-methods: Which methods to allow. Defaults to OPTIONS, HEAD, GET, POST, PUT, DELETE.

http.cors.allow-headers: Which headers to allow. Defaults to X-Requested-With, Content-Type, Content-Length.

http.cors.allow-credentials: Whether the Access-Control-Allow-Credentials header should be returned. Defaults to false.

This header is only returned when the setting is set to true.

http.detailed_errors.enabled

If true, enables the output of detailed error messages and stack traces in the response output. Defaults to true.

If false, use the error_trace parameter to enable stack traces and return detailed error messages. Otherwise, only a simple message will be returned.

http.pipelining.max_events

The maximum number of events to be queued up in memory before an HTTP connection is closed, defaults to 10000.

http.max_warning_header_count

The maximum number of warning headers in client HTTP responses. Defaults to unbounded.

http.max_warning_header_size

The maximum total size of warning headers in client HTTP responses. Defaults to unbounded.

REST request tracer

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The HTTP layer has a dedicated tracer logger which, when activated, logs incoming requests. The log can be dynamically activated by setting the level of the org.elasticsearch.http.HttpTracer logger to TRACE:

PUT _cluster/settings
{
   "transient" : {
      "logger.org.elasticsearch.http.HttpTracer" : "TRACE"
   }
}

You can also control which uris will be traced, using a set of include and exclude wildcard patterns. By default every request will be traced.

PUT _cluster/settings
{
   "transient" : {
      "http.tracer.include" : "*",
      "http.tracer.exclude" : ""
   }
}

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