Github user GJL commented on a diff in the pull request:
https://github.com/apache/flink/pull/5451#discussion_r169071363
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/async/AbstractAsynchronousOperationHandlers.java
---
@@ -0,0 +1,298 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.runtime.rest.handler.async;
+
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.api.common.time.Time;
+import org.apache.flink.runtime.concurrent.FutureUtils;
+import org.apache.flink.runtime.rest.NotFoundException;
+import org.apache.flink.runtime.rest.handler.AbstractRestHandler;
+import org.apache.flink.runtime.rest.handler.HandlerRequest;
+import org.apache.flink.runtime.rest.handler.RestHandlerException;
+import org.apache.flink.runtime.rest.messages.EmptyRequestBody;
+import org.apache.flink.runtime.rest.messages.MessageHeaders;
+import org.apache.flink.runtime.rest.messages.MessageParameters;
+import org.apache.flink.runtime.rest.messages.RequestBody;
+import org.apache.flink.runtime.rest.messages.TriggerId;
+import org.apache.flink.runtime.webmonitor.RestfulGateway;
+import org.apache.flink.runtime.webmonitor.retriever.GatewayRetriever;
+import org.apache.flink.types.Either;
+import org.apache.flink.util.FlinkException;
+
+import org.apache.flink.shaded.guava18.com.google.common.cache.Cache;
+import
org.apache.flink.shaded.guava18.com.google.common.cache.CacheBuilder;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.ThreadSafe;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * HTTP handlers for asynchronous operations.
+ *
+ * <p>Some operations long-running. To avoid blocking HTTP
--- End diff --
nit: grammatical error: *Some operations long-running*
---
