Apache http-client I/O reactor errorsedit

Sending requests can sometimes fail with one of the following errors, coming from the Apache http-client library:

  • Request cannot be executed; I/O reactor status: STOPPED
  • I/O reactor terminated abnormally
  • I/O reactor has been shut down

The I/O Reactor is the internal event loop in the http client library. It can terminate when an application callback throws an Error, like an OutOfMemoryError or a StackOverflowError. Remember that Error is different from a regular Exception and – quoting the Java documentationindicates serious problems that a reasonable application should not try to catch.

In the context of the Elasticsearch Java clients, this can happen on two occasions:

  • the application calls the low level RestClient directly, using the asynchronous performRequestAsync method, and an Error is thrown in the ResponseListener provided by the application.
  • an OutOfMemoryError happens while buffering the body of an http response.

In the first case, it is the application’s responsibility to catch Error in its ResponseListener and decide what to do when these errors happen.

The second case is taken care of in the Java API Client since version 8.12: the error is wrapped in a RuntimeException that is reported to the application.

In previous versions of the Java API Client, you can copy/paste the SafeResponseConsumer class in your project and initialize the RestClientTransport as follows:

RestClient restClient = ...
JsonpMapper mapper = ...
RestClientOptions options = new RestClientOptions(
RestClientTransport transport = new RestClientTransport(
    restClient, mapper, options