Added minimal docs for reindex api in java-api docs

Additionally:
* Included the existing update by query java api docs in java-api docs.
  (for some reason it was never included, it needed some tweaking and
  then it was good to go)
* moved delete-by-query / update-by-query code samples to java file so
  that we can verify that these samples at least compile.

Closes #24203

Author: martijnvg

docs/java-api/docs.asciidoc

@@ -7,12 +7,14 @@ This section describes the following CRUD APIs:
 * <<java-docs-index>>
 * <<java-docs-get>>
 * <<java-docs-delete>>
-* <<java-docs-delete-by-query>>
 * <<java-docs-update>>
 
 .Multi-document APIs
 * <<java-docs-multi-get>>
 * <<java-docs-bulk>>
+* <<java-docs-reindex>>
+* <<java-docs-update-by-query>>
+* <<java-docs-delete-by-query>>
 
 NOTE: All CRUD APIs are single-index APIs. The `index` parameter accepts a single
 index name, or an `alias` which points to a single index.
@@ -28,3 +30,7 @@ include::docs/update.asciidoc[]
 include::docs/multi-get.asciidoc[]
 
 include::docs/bulk.asciidoc[]
+
+include::docs/update-by-query.asciidoc[]
+
+include::docs/reindex.asciidoc[]

docs/java-api/docs/delete.asciidoc

@@ -42,15 +42,9 @@ DeleteResponse response = client.prepareDelete("twitter", "tweet", "1")
 The delete by query API allows one to delete a given set of documents based on
 the result of a query:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-BulkByScrollResponse response =
-    DeleteByQueryAction.INSTANCE.newRequestBuilder(client)
-        .filter(QueryBuilders.matchQuery("gender", "male")) <1>
-        .source("persons")                                  <2>
-        .get();                                             <3>
-
-long deleted = response.getDeleted();                       <4>
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[delete-by-query-sync]
 --------------------------------------------------
 <1> query
 <2> index
@@ -60,21 +54,9 @@ long deleted = response.getDeleted();                       <4>
 As it can be a long running operation, if you wish to do it asynchronously, you can call `execute` instead of `get`
 and provide a listener like:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-DeleteByQueryAction.INSTANCE.newRequestBuilder(client)
-    .filter(QueryBuilders.matchQuery("gender", "male"))                  <1>
-    .source("persons")                                                   <2>
-    .execute(new ActionListener<BulkByScrollResponse>() {           <3>
-        @Override
-        public void onResponse(BulkByScrollResponse response) {
-            long deleted = response.getDeleted();                        <4>
-        }
-        @Override
-        public void onFailure(Exception e) {
-            // Handle the exception
-        }
-    });
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[delete-by-query-async]
 --------------------------------------------------
 <1> query
 <2> index

docs/java-api/docs/reindex.asciidoc

@@ -0,0 +1,11 @@
+[[java-docs-reindex]]
+=== Reindex API
+
+See {ref}/docs-reindex.html[reindex API].
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[reindex1]
+--------------------------------------------------
+<1> Optionally a query can provided to filter what documents should be
+    re-indexed from the source to the target index.

docs/java-api/docs/update-by-query.asciidoc

@@ -1,18 +1,13 @@
-[[docs-update-by-query]]
-== Update By Query API
+[[java-docs-update-by-query]]
+=== Update By Query API
 
 The simplest usage of `updateByQuery` updates each
 document in an index without changing the source. This usage enables
-<<picking-up-a-new-property,picking up a new property>> or another online
-mapping change.
+picking up a new property or another online mapping change.
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.source("source_index").abortOnVersionConflict(false);
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query]
 --------------------------------------------------
 
 Calls to the `updateByQuery` API start by getting a snapshot of the index, indexing
@@ -41,78 +36,50 @@ The `UpdateByQueryRequestBuilder` API supports filtering the updated documents,
 limiting the total number of documents to update, and updating documents
 with a script:
 
-[source,java]
---------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
 
-updateByQuery.source("source_index")
-        .filter(termQuery("level", "awesome"))
-        .size(1000)
-        .script(new Script("ctx._source.awesome = 'absolutely'", ScriptType.INLINE, "painless", emptyMap()));
-
-BulkByScrollResponse response = updateByQuery.get();
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-filter]
 --------------------------------------------------
 
 `UpdateByQueryRequestBuilder` also enables direct access to the query used
 to select the documents. You can use this access to change the default scroll size or
 otherwise modify the request for matching documents.
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.source("source_index")
-        .source().setSize(500);
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-size]
 --------------------------------------------------
 
 You can also combine `size` with sorting to limit the documents updated:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.source("source_index").size(100)
-        .source().addSort("cat", SortOrder.DESC);
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-sort]
 --------------------------------------------------
 
 In addition to changing the `_source` field for the document, you can use a
 script to change the action, similar to the Update API:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.source("source_index")
-        .script(new Script(
-            "if (ctx._source.awesome == 'absolutely) {"
-          + "  ctx.op='noop'
-          + "} else if (ctx._source.awesome == 'lame') {"
-          + "  ctx.op='delete'"
-          + "} else {"
-          + "ctx._source.awesome = 'absolutely'}", ScriptType.INLINE, "painless", emptyMap()));
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-script]
 --------------------------------------------------
 
-As in the <<docs-update,Update API>>, you can set the value of `ctx.op` to change the
+As in the <<java-docs-update,Update API>>, you can set the value of `ctx.op` to change the
 operation that executes:
 
 `noop`::
 
 Set `ctx.op = "noop"` if your script doesn't make any
 changes. The `updateByQuery` operaton then omits that document from the updates.
-This behavior increments the `noop` counter in the
-<<docs-update-by-query-response-body, response body>>.
+This behavior increments the `noop` counter in the response body.
 
 `delete`::
 
 Set `ctx.op = "delete"` if your script decides that the document must be
 deleted. The deletion will be reported in the `deleted` counter in the
-<<docs-update-by-query-response-body, response body>>.
+response body.
 
 Setting `ctx.op` to any other value generates an error. Setting any
 other field in `ctx` generates an error.
@@ -123,79 +90,55 @@ from its original location.
 
 You can also perform these operations on multiple indices and types at once, similar to the search API:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.source("foo", "bar").source().setTypes("a", "b");
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-multi-index]
 --------------------------------------------------
 
 If you provide a `routing` value then the process copies the routing value to the scroll query,
 limiting the process to the shards that match that routing value:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.source().setRouting("cat");
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-routing]
 --------------------------------------------------
 
-`updateByQuery` can also use the <<ingest>> feature by
+`updateByQuery` can also use the ingest node by
 specifying a `pipeline` like this:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-UpdateByQueryRequestBuilder updateByQuery = UpdateByQueryAction.INSTANCE.newRequestBuilder(client);
-
-updateByQuery.setPipeline("hurray");
-
-BulkByScrollResponse response = updateByQuery.get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-pipeline]
 --------------------------------------------------
 
 [float]
-[[docs-update-by-query-task-api]]
+[[java-docs-update-by-query-task-api]]
 === Works with the Task API
 
-You can fetch the status of all running update-by-query requests with the
-<<tasks,Task API>>:
+You can fetch the status of all running update-by-query requests with the Task API:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-ListTasksResponse tasksList = client.admin().cluster().prepareListTasks()
-        .setActions(UpdateByQueryAction.NAME).setDetailed(true).get();
-
-for (TaskInfo info: tasksList.getTasks()) {
-    TaskId taskId = info.getTaskId();
-    BulkByScrollTask.Status status = (BulkByScrollTask.Status) info.getStatus();
-    // do stuff
-}
-
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-list-tasks]
 --------------------------------------------------
 
 With the `TaskId` shown above you can look up the task directly:
 
 // provide API Example
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-GetTaskResponse get = client.admin().cluster().prepareGetTask(taskId).get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-get-task]
 --------------------------------------------------
 
 [float]
-[[docs-update-by-query-cancel-task-api]]
+[[java-docs-update-by-query-cancel-task-api]]
 === Works with the Cancel Task API
 
-Any Update By Query can be canceled using the <<tasks,Task Cancel API>>:
+Any Update By Query can be canceled using the Task Cancel API:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-// Cancel all update-by-query requests
-client.admin().cluster().prepareCancelTasks().setActions(UpdateByQueryAction.NAME).get().getTasks()
-// Cancel a specific update-by-query request
-client.admin().cluster().prepareCancelTasks().setTaskId(taskId).get().getTasks()
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-cancel-task]
 --------------------------------------------------
 
 Use the `list tasks` API to find the value of `taskId`.
@@ -204,14 +147,14 @@ Cancelling a request is typically a very fast process but can take up to a few s
 The task status API continues to list the task until the cancellation is complete.
 
 [float]
-[[docs-update-by-query-rethrottle]]
+[[java-docs-update-by-query-rethrottle]]
 === Rethrottling
 
 Use the `_rethrottle` API to change the value of `requests_per_second` on a running update:
 
-[source,java]
+["source","java",subs="attributes,callouts,macros"]
 --------------------------------------------------
-RethrottleAction.INSTANCE.newRequestBuilder(client).setTaskId(taskId).setRequestsPerSecond(2.0f).get();
+include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-rethrottle]
 --------------------------------------------------
 
 Use the `list tasks` API to find the value of `taskId`.

docs/java-api/index.asciidoc

@@ -152,6 +152,8 @@ and add it as a dependency. As an example, we will use the `slf4j-simple` logger
 
 :client-tests: {docdir}/../../server/src/test/java/org/elasticsearch/client/documentation
 
+:client-reindex-tests: {docdir}/../../modules/reindex/src/test/java/org/elasticsearch/client/documentation
+
 include::client.asciidoc[]
 
 include::docs.asciidoc[]