blocking-async.md

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Blocking and asynchronous clients [blocking-and-async]

API clients come in two flavors: blocking and asynchronous. All methods on asynchronous clients return a standard CompletableFuture.

Both flavors can be used at the same time depending on your needs, sharing the same transport object:

% :::{include-code} src={{doc-tests-src}}/api_conventions/ApiConventionsTest.java tag=blocking-and-async

// Synchronous blocking client
ElasticsearchClient esClient = new ElasticsearchClient(transport);

if (esClient.exists(b -> b.index("products").id("foo")).value()) {
    logger.info("product exists");
}

// Asynchronous non-blocking client
ElasticsearchAsyncClient asyncClient =
    new ElasticsearchAsyncClient(transport);

asyncClient
    .exists(b -> b.index("products").id("foo"))
    .whenComplete((response, exception) -> {
        if (exception != null) {
            logger.error("Failed to index", exception);
        } else {
            logger.info("Product exists");
        }
    });

Although we won’t go in deeper details on asynchronous programming in Java, remember to handle failures of asynchronous tasks. It’s easy to overlook them and have errors go unnoticed.

:::{include} /reference/_snippets/doc-tests-blurb.md :::