[GitHub] [flink] StephanEwen commented on a change in pull request #8925: [FLINK-12852][network] Fix the deadlock occured when requesting exclusive buffers

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StephanEwen commented on a change in pull request #8925: [FLINK-12852][network] Fix the deadlock occured when requesting exclusive buffers
URL: https://github.com/apache/flink/pull/8925#discussion_r302035513
 
 

 ##########
 File path: flink-runtime/src/test/java/org/apache/flink/runtime/io/network/buffer/NetworkBufferPoolTest.java
 ##########
 @@ -477,4 +477,46 @@ public void go() throws Exception {
 			globalPool.destroy();
 		}
 	}
+
+	/**
+	 * Tests {@link NetworkBufferPool#requestMemorySegments()} and verifies it will end exceptionally
+	 * when failing to acquire all the segments in the specific timeout.
+	 */
+	@Test
+	public void testRequestMemorySegmentsTimeout() throws Exception {
+		final int numBuffers = 10;
+		final int numberOfSegmentsToRequest = 2;
+		final long requestSegmentsTimeoutInMillis = 1000L;
+
+		NetworkBufferPool globalPool = new NetworkBufferPool(
+				numBuffers,
+				128,
+				numberOfSegmentsToRequest,
+				requestSegmentsTimeoutInMillis);
+
+		BufferPool localBufferPool = globalPool.createBufferPool(0, numBuffers);
+		for (int i = 0; i < numBuffers; ++i) {
+			localBufferPool.requestBuffer();
+		}
+
+		assertEquals(0, globalPool.getNumberOfAvailableMemorySegments());
+
+		CheckedThread asyncRequest = new CheckedThread() {
+			@Override
+			public void go() throws Exception {
+				globalPool.requestMemorySegments();
+			}
+		};
+
+		asyncRequest.start();
+
+		try {
+			asyncRequest.trySync(requestSegmentsTimeoutInMillis * 10);
 
 Review comment:
   This probably leads to a flaky test. It should be okay to sync "forever" because if the feature is broken, the test will deadlock.

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