Performing requests
editPerforming requests
editOnce the RestClient
has been created, requests can be sent by calling either
performRequest
or performRequestAsync
. performRequest
is synchronous and
will block the calling thread and return the Response
when the request is
successful or throw an exception if it fails. performRequestAsync
is
asynchronous and accepts a ResponseListener
argument that it calls with a
Response
when the request is successful or with an Exception
if it fails.
This is synchronous:
And this is asynchronous:
Request request = new Request( "GET", "/"); Cancellable cancellable = restClient.performRequestAsync(request, new ResponseListener() { @Override public void onSuccess(Response response) { } @Override public void onFailure(Exception exception) { } });
The HTTP method ( |
|
The endpoint on the server |
|
Handle the response |
|
Handle the failure |
You can add request parameters to the request object:
request.addParameter("pretty", "true");
You can set the body of the request to any HttpEntity
:
request.setEntity(new NStringEntity( "{\"json\":\"text\"}", ContentType.APPLICATION_JSON));
The ContentType
specified for the HttpEntity
is important
because it will be used to set the Content-Type
header so that Elasticsearch
can properly parse the content.
You can also set it to a String
which will default to
a ContentType
of application/json
.
request.setJsonEntity("{\"json\":\"text\"}");
RequestOptions
editThe RequestOptions
class holds parts of the request that should be shared
between many requests in the same application. You can make a singleton
instance and share it between all requests:
private static final RequestOptions COMMON_OPTIONS; static { RequestOptions.Builder builder = RequestOptions.DEFAULT.toBuilder(); builder.addHeader("Authorization", "Bearer " + TOKEN); builder.setHttpAsyncResponseConsumerFactory( new HttpAsyncResponseConsumerFactory .HeapBufferedResponseConsumerFactory(30 * 1024 * 1024 * 1024)); COMMON_OPTIONS = builder.build(); }
addHeader
is for headers that are required for authorization or to work with
a proxy in front of Elasticsearch. There is no need to set the Content-Type
header because the client will automatically set that from the HttpEntity
attached to the request.
You can set the NodeSelector
which controls which nodes will receive
requests. NodeSelector.SKIP_DEDICATED_MASTERS
is a good choice.
You can also customize the response consumer used to buffer the asynchronous responses. The default consumer will buffer up to 100MB of response on the JVM heap. If the response is larger then the request will fail. You could, for example, lower the maximum size which might be useful if you are running in a heap constrained environment like the example above.
Once you’ve created the singleton you can use it when making requests:
request.setOptions(COMMON_OPTIONS);
You can also customize these options on a per request basis. For example, this adds an extra header:
RequestOptions.Builder options = COMMON_OPTIONS.toBuilder(); options.addHeader("cats", "knock things off of other things"); request.setOptions(options);
Multiple parallel asynchronous actions
editThe client is quite happy to execute many actions in parallel. The following
example indexes many documents in parallel. In a real world scenario you’d
probably want to use the _bulk
API instead, but the example is illustrative.
final CountDownLatch latch = new CountDownLatch(documents.length); for (int i = 0; i < documents.length; i++) { Request request = new Request("PUT", "/posts/doc/" + i); //let's assume that the documents are stored in an HttpEntity array request.setEntity(documents[i]); restClient.performRequestAsync( request, new ResponseListener() { @Override public void onSuccess(Response response) { latch.countDown(); } @Override public void onFailure(Exception exception) { latch.countDown(); } } ); } latch.await();
Cancelling asynchronous requests
editThe performRequestAsync
method returns a Cancellable
that exposes a single
public method called cancel
. Such method can be called to cancel the on-going
request. Cancelling a request will result in aborting the http request through
the underlying http client. On the server side, this does not automatically
translate to the execution of that request being cancelled, which needs to be
specifically implemented in the API itself.
The use of the Cancellable
instance is optional and you can safely ignore this
if you don’t need it. A typical usecase for this would be using this together with
frameworks like Rx Java or the Kotlin’s suspendCancellableCoRoutine
. Cancelling
no longer needed requests is a good way to avoid putting unnecessary
load on Elasticsearch.