[GitHub] [incubator-uniffle] advancedxy commented on a diff in pull request #568: [#567] feat: add a shuffle-server metric about read_used_buffer_size

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

advancedxy commented on code in PR #568:
URL: https://github.com/apache/incubator-uniffle/pull/568#discussion_r1101058393


##########
server/src/main/java/org/apache/uniffle/server/buffer/ShuffleBufferManager.java:
##########
@@ -362,10 +363,12 @@ public boolean requireReadMemoryWithRetry(long size) {
   public void releaseReadMemory(long size) {
     if (readDataMemory.get() >= size) {
       readDataMemory.addAndGet(-size);
+      ShuffleServerMetrics.gaugeReadBufferUsedSize.dec(size);

Review Comment:
   In my opinion, the suggest might not be better than the previous one.
   
   Consider this case:
   ```
   T1, T2 for two threads.
   t0, t1, t2 for times
   N: current read buffer
   t0: T1: readDataMemory.addAndGet(-size)
   t1: T1: readDataMemory.get() --> N - size
   t2: T2: readDataMemory.addAndGet(-size)
   t3: T2: readDataMemory.get() --> N - size - size
   t4: T2 : gaugeReadBufferUsedSize <- N -size - size
   t5: T1:  gaugeReadBufferUsedSize  <- N - size
   ```
   
   Unless there's safe bet to actually reset the gauge to the readDataMemory.get().



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