Re: [PR] HBASE-29912 Codel lifoThreshold should be applied on soft queue limit… [hbase]

["Umeshkumar9414 (via GitHub)" <gi...@apache.org>]

Umeshkumar9414 commented on code in PR #7864:
URL: https://github.com/apache/hbase/pull/7864#discussion_r3354233780


##########
hbase-server/src/test/java/org/apache/hadoop/hbase/ipc/TestSimpleRpcScheduler.java:
##########
@@ -808,4 +838,161 @@ public void drop() {
       }
     };
   }
+
+  /**
+   * Test LIFO switching behavior through actual RPC calls. This test verifies that when the queue
+   * fills beyond the LIFO threshold, newer calls are processed before older calls (LIFO mode).
+   */
+  @Test
+  public void testCoDelLifoWithRpcCalls() throws Exception {
+    Configuration testConf = HBaseConfiguration.create();
+    testConf.set(RpcExecutor.CALL_QUEUE_TYPE_CONF_KEY,
+      RpcExecutor.CALL_QUEUE_TYPE_CODEL_CONF_VALUE);
+    int maxCallQueueLength = 50;
+    double coDelLifoThreshold = 0.8;
+    testConf.setInt(RpcScheduler.IPC_SERVER_MAX_CALLQUEUE_LENGTH, maxCallQueueLength);
+    testConf.setDouble(RpcExecutor.CALL_QUEUE_CODEL_LIFO_THRESHOLD, coDelLifoThreshold);
+    testConf.setInt(RpcExecutor.CALL_QUEUE_CODEL_TARGET_DELAY, 100);
+    testConf.setInt(RpcExecutor.CALL_QUEUE_CODEL_INTERVAL, 100);
+    testConf.setInt(HConstants.REGION_SERVER_HANDLER_COUNT, 1); // Single handler to control
+                                                                // processing
+
+    PriorityFunction priority = mock(PriorityFunction.class);
+    when(priority.getPriority(any(), any(), any())).thenReturn(HConstants.NORMAL_QOS);
+    SimpleRpcScheduler scheduler =
+      new SimpleRpcScheduler(testConf, 1, 0, 0, priority, HConstants.QOS_THRESHOLD);
+
+    try {
+      scheduler.init(CONTEXT);
+      scheduler.start();
+
+      // Track completion order
+      final List<Integer> completedCalls = Collections.synchronizedList(new ArrayList<>());
+
+      // Dispatch many slow calls rapidly to fill the queue beyond 80% threshold
+      // With queue limit of 50, we need > 40 calls to cross 80%
+      int numCalls = 48;
+      for (int i = 0; i < numCalls; i++) {
+        final int callId = i;
+        CallRunner call = createMockTask(HConstants.NORMAL_QOS);
+        call.setStatus(new MonitoredRPCHandlerImpl("test"));
+        doAnswer(invocation -> {
+          completedCalls.add(callId);
+          Thread.sleep(100); // Slow processing to allow queue to build up
+          return null;
+        }).when(call).run();
+        scheduler.dispatch(call);
+        // No delay between dispatches - rapidly fill the queue
+      }
+
+      // Wait for some calls to complete
+      await().atMost(2, TimeUnit.SECONDS).until(() -> completedCalls.size() >= 3);
+
+      // Check that we had LIFO switches
+      long lifoSwitches = scheduler.getNumLifoModeSwitches();
+      assertTrue(lifoSwitches > 0,
+        "Should have switched to LIFO mode at least once, but got: " + lifoSwitches);
+
+      // Verify LIFO behavior: Among first completed calls, we should see higher call IDs
+      // (indicating later dispatched calls completed first)
+      int maxCallIdCompleted = -1;
+      for (int i = 0; i < completedCalls.size(); i++) {
+        maxCallIdCompleted = Math.max(maxCallIdCompleted, completedCalls.get(i));
+      }
+      // At least one of the early completed calls should have a high ID (>20)
+      // indicating LIFO processing
+      assertTrue(maxCallIdCompleted > maxCallQueueLength * coDelLifoThreshold,
+        "Expected LIFO behavior: early completed calls should include call arrived after threshold "
+          + "maxCallIdCompleted: " + maxCallIdCompleted);
+
+    } finally {
+      scheduler.stop();
+    }
+  }
+
+  /**
+   * Test that CoDel queue returns to FIFO mode after draining below threshold.
+   */
+  @Test
+  public void testCoDelQueueDrainAndFifoReturn() throws Exception {

Review Comment:
   yeah, I agree, I missed it. There is also possibility that 101 can finish first as handler A got paused. So lets me just add assert for NumLifoModeSwitches.



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