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 settingsedit

The settings in the table below can be configured for HTTP. Note that none of them are dynamically updatable so for them to take effect they should be set in the Elasticsearch configuration file.

Setting Description


A bind port range. Defaults to 9200-9300.


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.


The host address to bind the HTTP service to. Defaults to (if set) or network.bind_host.


The host address to publish for HTTP clients to connect to. Defaults to (if set) or network.publish_host.

Used to set the http.bind_host and the http.publish_host.


The max content of an HTTP request. Defaults to 100mb.


The max length of an HTTP URL. Defaults to 4kb


The max size of allowed headers. Defaults to 8kB


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.


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.


Enable or disable cross-origin resource sharing, i.e. 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. Note that 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.


Which origins to allow. Defaults to no origins allowed. If you prepend and append a / 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. * is a valid value but is considered a security risk as your Elasticsearch instance is open to cross origin requests from anywhere.


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)


Which methods to allow. Defaults to OPTIONS, HEAD, GET, POST, PUT, DELETE.


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


Whether the Access-Control-Allow-Credentials header should be returned. Note: This header is only returned, when the setting is set to true. Defaults to false


Enables or disables the output of detailed error messages and stack traces in response output. Note: When set to false and the error_trace request parameter is specified, an error will be returned; when error_trace is not specified, a simple message will be returned. Defaults to true


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


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


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

It also uses the common network settings.

REST request traceredit

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" : {
      "" : "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" : ""