Added get pipeline API

Relates to #27205

(cherry picked from commit 696b0ab2d09d4d25806b3fbfd4f82b6fc9f7218b)

client/rest-high-level/src/main/java/org/elasticsearch/client/ClusterClient.java

@@ -23,6 +23,8 @@
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsRequest;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsResponse;
+import org.elasticsearch.action.ingest.GetPipelineRequest;
+import org.elasticsearch.action.ingest.GetPipelineResponse;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
 import org.elasticsearch.action.ingest.PutPipelineResponse;
 
@@ -87,4 +89,26 @@ public void putPipelineAsync(PutPipelineRequest request, ActionListener<PutPipel
         restHighLevelClient.performRequestAsyncAndParseEntity( request, RequestConverters::putPipeline,
             PutPipelineResponse::fromXContent, listener, emptySet(), headers);
     }
+
+    /**
+     * Get an existing pipeline
+     * <p>
+     * See
+     * <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/put-pipeline-api.html"> Get Pipeline API on elastic.co</a>
+     */
+    public GetPipelineResponse getPipeline(GetPipelineRequest request, Header... headers) throws IOException {
+        return restHighLevelClient.performRequestAndParseEntity( request, RequestConverters::getPipeline,
+            GetPipelineResponse::fromXContent, emptySet(), headers);
+    }
+
+    /**
+     * Asynchronously get an existing pipeline
+     * <p>
+     * See
+     * <a href="https://www.elastic.co/guide/en/elasticsearch/reference/master/get-pipeline-api.html"> Get Pipeline API on elastic.co</a>
+     */
+    public void getPipelineAsync(GetPipelineRequest request, ActionListener<GetPipelineResponse> listener, Header... headers) {
+        restHighLevelClient.performRequestAsyncAndParseEntity( request, RequestConverters::getPipeline,
+            GetPipelineResponse::fromXContent, listener, emptySet(), headers);
+    }
 }

client/rest-high-level/src/main/java/org/elasticsearch/client/RequestConverters.java

@@ -59,6 +59,7 @@
 import org.elasticsearch.action.get.MultiGetRequest;
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
+import org.elasticsearch.action.ingest.GetPipelineRequest;
 import org.elasticsearch.action.search.ClearScrollRequest;
 import org.elasticsearch.action.search.MultiSearchRequest;
 import org.elasticsearch.action.search.SearchRequest;
@@ -610,6 +611,18 @@ static Request clusterPutSettings(ClusterUpdateSettingsRequest clusterUpdateSett
         return request;
     }
 
+    static Request getPipeline(GetPipelineRequest getPipelineRequest) {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ingest/pipeline")
+            .addCommaSeparatedPathParts(getPipelineRequest.getIds())
+            .build();
+        Request request = new Request(HttpGet.METHOD_NAME, endpoint);
+
+        Params parameters = new Params(request);
+        parameters.withMasterTimeout(getPipelineRequest.masterNodeTimeout());
+        return request;
+    }
+
     static Request putPipeline(PutPipelineRequest putPipelineRequest) throws IOException {
         String endpoint = new EndpointBuilder()
             .addPathPartAsIs("_ingest/pipeline")

client/rest-high-level/src/test/java/org/elasticsearch/client/ClusterClientIT.java

@@ -22,6 +22,8 @@
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsRequest;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsResponse;
+import org.elasticsearch.action.ingest.GetPipelineRequest;
+import org.elasticsearch.action.ingest.GetPipelineResponse;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
 import org.elasticsearch.action.ingest.PutPipelineResponse;
 import org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider;
@@ -32,7 +34,7 @@
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.common.xcontent.support.XContentMapValues;
 import org.elasticsearch.indices.recovery.RecoverySettings;
-import org.elasticsearch.ingest.Pipeline;
+import org.elasticsearch.ingest.PipelineConfiguration;
 import org.elasticsearch.rest.RestStatus;
 
 import java.io.IOException;
@@ -113,31 +115,7 @@ public void testClusterUpdateSettingNonExistent() {
 
     public void testPutPipeline() throws IOException {
         String id = "some_pipeline_id";
-        XContentType xContentType = randomFrom(XContentType.values());
-        XContentBuilder pipelineBuilder = XContentBuilder.builder(xContentType.xContent());
-        pipelineBuilder.startObject();
-        {
-            pipelineBuilder.field(Pipeline.DESCRIPTION_KEY, "some random set of processors");
-            pipelineBuilder.startArray(Pipeline.PROCESSORS_KEY);
-            {
-                pipelineBuilder.startObject().startObject("set");
-                {
-                    pipelineBuilder
-                        .field("field", "foo")
-                        .field("value", "bar");
-                }
-                pipelineBuilder.endObject().endObject();
-                pipelineBuilder.startObject().startObject("convert");
-                {
-                    pipelineBuilder
-                        .field("field", "rank")
-                        .field("type", "integer");
-                }
-                pipelineBuilder.endObject().endObject();
-            }
-            pipelineBuilder.endArray();
-        }
-        pipelineBuilder.endObject();
+        XContentBuilder pipelineBuilder = buildRandomXContentPipeline();
         PutPipelineRequest request = new PutPipelineRequest(
             id,
             BytesReference.bytes(pipelineBuilder),
@@ -147,4 +125,27 @@ public void testPutPipeline() throws IOException {
             execute(request, highLevelClient().cluster()::putPipeline, highLevelClient().cluster()::putPipelineAsync);
         assertTrue(putPipelineResponse.isAcknowledged());
     }
+
+    public void testGetPipeline() throws IOException {
+        String id = "get_pipeline_id";
+        XContentBuilder pipelineBuilder = buildRandomXContentPipeline();
+        {
+            PutPipelineRequest request = new PutPipelineRequest(
+                id,
+                BytesReference.bytes(pipelineBuilder),
+                pipelineBuilder.contentType()
+            );
+            createPipeline(request);
+        }
+
+        GetPipelineRequest request = new GetPipelineRequest(id);
+
+        GetPipelineResponse response =
+            execute(request, highLevelClient().cluster()::getPipeline, highLevelClient().cluster()::getPipelineAsync);
+        assertTrue(response.isFound());
+        assertEquals(response.getPipelineConfigs().get(0).getId(), id);
+        PipelineConfiguration expectedConfig =
+            new PipelineConfiguration(id, BytesReference.bytes(pipelineBuilder), pipelineBuilder.contentType());
+        assertEquals(expectedConfig.getConfigAsMap(), response.getPipelineConfigs().get(0).getConfigAsMap());
+    }
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/ESRestHighLevelClientTestCase.java

@@ -21,7 +21,12 @@
 
 import org.apache.http.Header;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.ingest.PutPipelineRequest;
 import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.common.bytes.BytesReference;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentType;
+import org.elasticsearch.ingest.Pipeline;
 import org.elasticsearch.test.rest.ESRestTestCase;
 import org.junit.AfterClass;
 import org.junit.Before;
@@ -80,4 +85,42 @@ private HighLevelClient(RestClient restClient) {
             super(restClient, (client) -> {}, Collections.emptyList());
         }
     }
+
+    protected static XContentBuilder buildRandomXContentPipeline() throws IOException {
+        XContentType xContentType = randomFrom(XContentType.values());
+        XContentBuilder pipelineBuilder = XContentBuilder.builder(xContentType.xContent());
+        pipelineBuilder.startObject();
+        {
+            pipelineBuilder.field(Pipeline.DESCRIPTION_KEY, "some random set of processors");
+            pipelineBuilder.startArray(Pipeline.PROCESSORS_KEY);
+            {
+                pipelineBuilder.startObject().startObject("set");
+                {
+                    pipelineBuilder
+                        .field("field", "foo")
+                        .field("value", "bar");
+                }
+                pipelineBuilder.endObject().endObject();
+                pipelineBuilder.startObject().startObject("convert");
+                {
+                    pipelineBuilder
+                        .field("field", "rank")
+                        .field("type", "integer");
+                }
+                pipelineBuilder.endObject().endObject();
+            }
+            pipelineBuilder.endArray();
+        }
+        pipelineBuilder.endObject();
+        return pipelineBuilder;
+    }
+
+    protected static void createPipeline(String pipelineId) throws IOException {
+        XContentBuilder builder = buildRandomXContentPipeline();
+        createPipeline(new PutPipelineRequest(pipelineId, BytesReference.bytes(builder), builder.contentType()));
+    }
+
+    protected static void createPipeline(PutPipelineRequest putPipelineRequest) throws IOException {
+        assertOK(client().performRequest(RequestConverters.putPipeline(putPipelineRequest)));
+    }
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/RequestConvertersTests.java

@@ -61,6 +61,7 @@
 import org.elasticsearch.action.get.GetRequest;
 import org.elasticsearch.action.get.MultiGetRequest;
 import org.elasticsearch.action.index.IndexRequest;
+import org.elasticsearch.action.ingest.GetPipelineRequest;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
 import org.elasticsearch.action.search.ClearScrollRequest;
 import org.elasticsearch.action.search.MultiSearchRequest;
@@ -1425,6 +1426,20 @@ public void testPutPipeline() throws IOException {
         assertEquals(expectedParams, expectedRequest.getParameters());
     }
 
+    public void testGetPipeline() {
+        String pipelineId = "some_pipeline_id";
+        Map<String, String> expectedParams = new HashMap<>();
+        GetPipelineRequest request = new GetPipelineRequest("some_pipeline_id");
+        setRandomMasterTimeout(request, expectedParams);
+        Request expectedRequest = RequestConverters.getPipeline(request);
+        StringJoiner endpoint = new StringJoiner("/", "/", "");
+        endpoint.add("_ingest/pipeline");
+        endpoint.add(pipelineId);
+        assertEquals(endpoint.toString(), expectedRequest.getEndpoint());
+        assertEquals(HttpGet.METHOD_NAME, expectedRequest.getMethod());
+        assertEquals(expectedParams, expectedRequest.getParameters());
+    }
+
     public void testRollover() throws IOException {
         RolloverRequest rolloverRequest = new RolloverRequest(randomAlphaOfLengthBetween(3, 10),
                 randomBoolean() ? null : randomAlphaOfLengthBetween(3, 10));

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/ClusterClientDocumentationIT.java

@@ -23,6 +23,8 @@
 import org.elasticsearch.action.LatchedActionListener;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsRequest;
 import org.elasticsearch.action.admin.cluster.settings.ClusterUpdateSettingsResponse;
+import org.elasticsearch.action.ingest.GetPipelineRequest;
+import org.elasticsearch.action.ingest.GetPipelineResponse;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
 import org.elasticsearch.action.ingest.PutPipelineResponse;
 import org.elasticsearch.client.ESRestHighLevelClientTestCase;
@@ -34,6 +36,7 @@
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.indices.recovery.RecoverySettings;
+import org.elasticsearch.ingest.PipelineConfiguration;
 
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
@@ -257,4 +260,74 @@ public void onFailure(Exception e) {
             assertTrue(latch.await(30L, TimeUnit.SECONDS));
         }
     }
+
+    public void testGetPipeline() throws IOException {
+        RestHighLevelClient client = highLevelClient();
+
+        {
+            createPipeline("my-pipeline-id");
+        }
+
+        {
+            // tag::get-pipeline-request
+            GetPipelineRequest request = new GetPipelineRequest("my-pipeline-id"); // <1>
+            // end::end-pipeline-request
+
+            // tag::get-pipeline-request-masterTimeout
+            request.masterNodeTimeout(TimeValue.timeValueMinutes(1)); // <1>
+            request.masterNodeTimeout("1m"); // <2>
+            // end::get-pipeline-request-masterTimeout
+
+            // tag::get-pipeline-execute
+            GetPipelineResponse response = client.cluster().getPipeline(request); // <1>
+            // end::get-pipeline-execute
+
+            // tag::get-pipeline-response
+            boolean successful = response.isFound(); // <1>
+            List<PipelineConfiguration> pipelines = response.getPipelineConfigs(); // <2>
+            for(PipelineConfiguration pipeline: pipelines) {
+                Map<String, Object> config = pipeline.getConfigAsMap(); // <3>
+            }
+            // end::get-pipeline-response
+
+            assertTrue(successful);
+        }
+    }
+
+    public void testGetPipelineAsync() throws Exception {
+        RestHighLevelClient client = highLevelClient();
+
+        {
+            createPipeline("my-pipeline-id");
+        }
+
+        {
+            GetPipelineRequest request = new GetPipelineRequest("my-pipeline-id");
+
+            // tag::get-pipeline-execute-listener
+            ActionListener<GetPipelineResponse> listener =
+                new ActionListener<GetPipelineResponse>() {
+                    @Override
+                    public void onResponse(GetPipelineResponse response) {
+                        // <1>
+                    }
+
+                    @Override
+                    public void onFailure(Exception e) {
+                        // <2>
+                    }
+                };
+            // end::get-pipeline-execute-listener
+
+            // Replace the empty listener by a blocking listener in test
+            final CountDownLatch latch = new CountDownLatch(1);
+            listener = new LatchedActionListener<>(listener, latch);
+
+            // tag::get-pipeline-execute-async
+            client.cluster().getPipelineAsync(request, listener); // <1>
+            // end::get-pipeline-execute-async
+
+            assertTrue(latch.await(30L, TimeUnit.SECONDS));
+        }
+    }
 }

docs/java-rest/high-level/cluster/get_pipeline.asciidoc

@@ -0,0 +1,75 @@
+[[java-rest-high-cluster-get-pipeline]]
+=== Get Pipeline API
+
+[[java-rest-high-cluster-get-pipeline-request]]
+==== Get Pipeline Request
+
+A `GetPipelineRequest` requires one or more `pipelineIds` to fetch.
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/ClusterClientDocumentationIT.java[get-pipeline-request]
+--------------------------------------------------
+<1> The pipeline id to fetch
+
+==== Optional arguments
+The following arguments can optionally be provided:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/ClusterClientDocumentationIT.java[get-pipeline-request-masterTimeout]
+--------------------------------------------------
+<1> Timeout to connect to the master node as a `TimeValue`
+<2> Timeout to connect to the master node as a `String`
+
+[[java-rest-high-cluster-get-pipeline-sync]]
+==== Synchronous Execution
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/ClusterClientDocumentationIT.java[get-pipeline-execute]
+--------------------------------------------------
+<1> Execute the request and get back the response in a GetPipelineResponse object.
+
+[[java-rest-high-cluster-get-pipeline-async]]
+==== Asynchronous Execution
+
+The asynchronous execution of a get pipeline request requires both the `GetPipelineRequest`
+instance and an `ActionListener` instance to be passed to the asynchronous
+method:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/ClusterClientDocumentationIT.java[get-pipeline-execute-async]
+--------------------------------------------------
+<1> The `GetPipelineRequest` to execute and the `ActionListener` to use when
+the execution completes
+
+The asynchronous method does not block and returns immediately. Once it is
+completed the `ActionListener` is called back using the `onResponse` method
+if the execution successfully completed or using the `onFailure` method if
+it failed.
+
+A typical listener for `GetPipelineResponse` looks like:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/ClusterClientDocumentationIT.java[get-pipeline-execute-listener]
+--------------------------------------------------
+<1> Called when the execution is successfully completed. The response is
+provided as an argument
+<2> Called in case of failure. The raised exception is provided as an argument
+
+[[java-rest-high-cluster-get-pipeline-response]]
+==== Get Pipeline Response
+
+The returned `GetPipelineResponse` allows to retrieve information about the executed
+ operation as follows:
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests}/ClusterClientDocumentationIT.java[get-pipeline-response]
+--------------------------------------------------
+<1> Check if a matching pipeline id was found or not.
+<2> Get the list of pipelines found as a list of `PipelineConfig` objects.
+<3> Get the individual configuration of each pipeline as a `Map<String, Object>`.