How can I make Jest handle an ElasticSearch server being unavailable?

Question

I currently configure Jest by giving it a list of server URIs. Like this:

 public JestClient jestClient() {
    final JestClientFactory factory = new JestClientFactory();
    factory.setHttpClientConfig(new HttpClientConfig
            .Builder(esServerUris)
            .build());
    final JestClient jestClient = factory.getObject();
    return jestClient;
}

If one of my ElasticSearch servers go offline (e.g. failure or maintenance), then a percentage of my Jest queries fail. Jest doesn't seem to do any kind of intelligent connection management by default.It must do something like round-robin through the servers or pick a server at random.

Is there a better way to handle this?

Answer 1

You need to enable discovery in order for the client factory to find another server in case one goes down. Something like this should do:

public JestClient jestClient() {
    final JestClientFactory factory = new JestClientFactory();
    factory.setHttpClientConfig(new HttpClientConfig
            .Builder(esServerUris)
            .discoveryEnabled(true)
            .discoveryFrequency(500l, TimeUnit.MILLISECONDS)
            .build());
    final JestClient jestClient = factory.getObject();
    return jestClient;
}

You can also see how they're testing this in JestClientFactoryIntegrationTest.java, i.e. they start with a single node, then add 3 more nodes, then bring one node down and assert that the client still has a valid connection to a node that is up.