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Posted to issues@flink.apache.org by "nattilabalint (via GitHub)" <gi...@apache.org> on 2026/05/29 08:25:23 UTC

[PR] [FLINK-39761][runtime] Set 'Connection: close' header when sending '304 Not Modified' responses [flink]

nattilabalint opened a new pull request, #28275:
URL: https://github.com/apache/flink/pull/28275

   ## What is the purpose of the change
   
   Fix the proxy connection pool poisoning (putting back closed connections to the pool) on 304 Not Modified responses.
   This is happening, because Flink severe the connections from its end when respond with HTTP_304, without explicitly setting the Connection: close header on the response.
   
   ## Brief change log
   
   The Connection: close header added to the response.
   
   ## Verifying this change
   
   This change added tests and can be verified as follows:
   
     - Added unit test to verify the Connection: close header
     - The proxy connection pool poisoning related errors disappeared (repro env: Flink dashboard behind Knox, browser reload sends 'If-Modified-Since' header for cached static assets (.js, .css), Flink respond with HTTP_304, no failed subsequent GET failures anymore)
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): no
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: no
     - The serializers: no
     - The runtime per-record code paths (performance sensitive): no
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
     - The S3 file system connector: no
   
   ## Documentation
   
     - Does this pull request introduce a new feature? no
     - If yes, how is the feature documented? not applicable
   
   ---
   
   ##### Was generative AI tooling used to co-author this PR?
   
   - [X] Yes (please specify the tool below)
   
   Generated-by: Gemini 3.5
   


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Re: [PR] [FLINK-39761][runtime] Set 'Connection: close' header when sending '304 Not Modified' responses [flink]

Posted by "flinkbot (via GitHub)" <gi...@apache.org>.
flinkbot commented on PR #28275:
URL: https://github.com/apache/flink/pull/28275#issuecomment-4572599651

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   ## CI report:
   
   * 252b2a5803c7e1d7a33565021a3845fc4400cc64 UNKNOWN
   
   <details>
   <summary>Bot commands</summary>
     The @flinkbot bot supports the following commands:
   
    - `@flinkbot run azure` re-run the last Azure build
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Re: [PR] [FLINK-39761][runtime] Set 'Connection: close' header when sending '304 Not Modified' responses [flink]

Posted by "spuru9 (via GitHub)" <gi...@apache.org>.
spuru9 commented on code in PR #28275:
URL: https://github.com/apache/flink/pull/28275#discussion_r3324307769


##########
flink-runtime/src/test/java/org/apache/flink/runtime/rest/handler/legacy/files/StaticFileServerHandlerTest.java:
##########
@@ -0,0 +1,68 @@
+/*
+ * 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.legacy.files;
+
+import org.apache.flink.shaded.netty4.io.netty.channel.ChannelFuture;
+import org.apache.flink.shaded.netty4.io.netty.channel.ChannelHandlerContext;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.FullHttpResponse;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaderNames;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaderValues;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;

Review Comment:
   The test correctly targets JUnit 5 (org.junit.jupiter), but two conventions are off for new Flink test code:
     1. Drop public on the class and the `@Test` method — JUnit 5 doesn't require it and Flink's style drops it.
     2. Use AssertJ, not Jupiter Assertions. Flink standardizes on AssertJ (assertThat(...)).



##########
flink-runtime/src/test/java/org/apache/flink/runtime/rest/handler/legacy/files/StaticFileServerHandlerTest.java:
##########
@@ -0,0 +1,68 @@
+/*
+ * 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.legacy.files;
+
+import org.apache.flink.shaded.netty4.io.netty.channel.ChannelFuture;
+import org.apache.flink.shaded.netty4.io.netty.channel.ChannelHandlerContext;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.FullHttpResponse;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaderNames;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpHeaderValues;
+import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class StaticFileServerHandlerTest {
+
+    @Test
+    public void testSendNotModifiedIncludesConnectionCloseHeader() {

Review Comment:
   Test uses Mockito, which Flink forbids via checkstyle
   https://flink.apache.org/how-to-contribute/code-style-and-quality-common/#avoid-mockito---use-reusable-test-implementations



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Re: [PR] [FLINK-39761][runtime] Set 'Connection: close' header when sending '304 Not Modified' responses [flink]

Posted by "ferenc-csaky (via GitHub)" <gi...@apache.org>.
ferenc-csaky merged PR #28275:
URL: https://github.com/apache/flink/pull/28275


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Re: [PR] [FLINK-39761][runtime] Set 'Connection: close' header when sending '304 Not Modified' responses [flink]

Posted by "ferenc-csaky (via GitHub)" <gi...@apache.org>.
ferenc-csaky commented on PR #28275:
URL: https://github.com/apache/flink/pull/28275#issuecomment-4605969331

   @flinkbot run azure


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Re: [PR] [FLINK-39761][runtime] Set 'Connection: close' header when sending '304 Not Modified' responses [flink]

Posted by "nattilabalint (via GitHub)" <gi...@apache.org>.
nattilabalint commented on PR #28275:
URL: https://github.com/apache/flink/pull/28275#issuecomment-4626660475

   @flinkbot run azure


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