Github user uce commented on a diff in the pull request:
https://github.com/apache/flink/pull/6031#discussion_r190244366
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/router/MethodlessRouter.java
---
@@ -0,0 +1,121 @@
+/*
+ * 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.router;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+
+/**
+ * This is adopted and simplified code from tv.cntt:netty-router library.
For more information check {@link Router}.
+ *
+ * <p>Router that doesn't contain information about HTTP request methods
and route
+ * matching orders.
+ */
+final class MethodlessRouter<T> {
+ private static final Logger log =
LoggerFactory.getLogger(MethodlessRouter.class);
+
+ // A path pattern can only point to one target
+ private final Map<PathPattern, T> routes = new LinkedHashMap<>();
--- End diff --
Please correct me if I'm wrong but I have a question regarding memory
visibility: The thread that updates this map and the Netty event loop threads
are different, so there might theoretically be a memory visibility issue if
routes are added after the router has been passed to the `RouterHandler`. I
don't think that we do this currently, but the API theoretically allows it. I'm
wondering whether it makes sense to make the routes immutable, maybe something
like creating the routes with a builder:
```java
Routes routes = new RoutesBuilder()
.addGet(...)
...
.build();
Router router = new Router(routes);
```
Or use a thread-safe map here that also preserves ordering (maybe wrap
using `synchronizedMap`).
---
Since we currently rely on correct registration order (e.g.
`/jobs/overview` before `/jobs/:id` for correct matching), the immutable
approach would allow us to include a utility in `Routes` that sorts pattern as
done in `RestServerEndpoint:143`:
```java
Collections.sort(handlers,RestHandlerUrlComparator.INSTANCE);
```
---
