Document HTTP/2 support (#330)

* Document HTTP/2 support Signed-off-by: Andriy Redko <[email protected]> * Addressing code review comments Signed-off-by: Andriy Redko <[email protected]> Signed-off-by: Andriy Redko <[email protected]>
opensearch-project · Jan 18, 2023 · 04beb24 · 04beb24
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -9,6 +9,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Add 1-click release workflows ([#321](https://github.com/opensearch-project/opensearch-java/pull/321))
 - Introduce new OpenSearchTransport based on Apache HttpClient 5 ([#281](https://github.com/opensearch-project/opensearch-java/pull/281))
 - Add workflow to publish snapshots via GHA ([#325](https://github.com/opensearch-project/opensearch-java/pull/325))
+- Document HTTP/2 support ([#330](https://github.com/opensearch-project/opensearch-java/pull/330))
 
 ### Dependencies
 - Bumps `classgraph` from 4.8.149 to 4.8.154

diff --git a/USER_GUIDE.md b/USER_GUIDE.md
@@ -56,28 +56,46 @@ There are multiple low level transports which `OpenSearchClient` could be config
 ### Create a client using `RestClientTransport`
 
 ```java
-Transport transport = new RestClientTransport(restClient, new JacksonJsonpMapper()); 
+OpenSearchTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper()); 
 OpenSearchClient client = new OpenSearchClient(transport);
 ```
 
 The `JacksonJsonpMapper` class (2.x versions) only supports Java 7 objects by default. [Java 8 modules](https://github.com/FasterXML/jackson-modules-java8) to support JDK8 classes such as the Date and Time API (JSR-310), `Optional`, and more can be used by including [the additional datatype dependency](https://github.com/FasterXML/jackson-modules-java8#usage) and adding the module.  For example, to include JSR-310 classes:
 
 ```java
-Transport transport = new RestClientTransport(restClient,
+OpenSearchTransport transport = new RestClientTransport(restClient,
     new JacksonJsonpMapper(new ObjectMapper().registerModule(new JavaTimeModule()))); 
 OpenSearchClient client = new OpenSearchClient(transport);
 ```
 
+Upcoming OpenSearch `3.0.0` release brings HTTP/2 support and as such, the `RestClientTransport` would switch to HTTP/2 if available (for both HTTPS and/or HTTP protocols). The desired protocol could be forced using `RestClientBuilder.HttpClientConfigCallback`.
+
 ### Create a client using `ApacheHttpClient5Transport`
 
 ```java
-final Transport transport = ApacheHttpClient5TransportBuilder
+final OpenSearchTransport transport = ApacheHttpClient5TransportBuilder
     .builder(hosts)
     .setMapper(new JacksonJsonpMapper())
     .build();
 OpenSearchClient client = new OpenSearchClient(transport);
 ```
 
+Upcoming OpenSearch `3.0.0` release brings HTTP/2 support and as such, the `ApacheHttpClient5Transport` would switch to HTTP/2 if available (for both HTTPS and/or HTTP protocols). The desired protocol could be forced using `ApacheHttpClient5TransportBuilder.HttpClientConfigCallback`, for example:
+
+```java
+final OpenSearchTransport transport = ApacheHttpClient5TransportBuilder
+    .builder(httpHost)
+    .setMapper(new JacksonJsonpMapper())
+    .setHttpClientConfigCallback(new ApacheHttpClient5TransportBuilder.HttpClientConfigCallback() {
+        @Override
+        public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
+            return httpClientBuilder.setVersionPolicy(HttpVersionPolicy.FORCE_HTTP_2);
+        }
+    })
+    .build();
+OpenSearchClient client = new OpenSearchClient(transport);
+```
+
 ## Create an index
 
 ```java