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Posted to issues@fluss.apache.org by "loserwang1024 (via GitHub)" <gi...@apache.org> on 2026/09/20 11:57:48 UTC

[PR] [client][metrics] Expose record accumulator memory usage metrics. [fluss]

loserwang1024 opened a new pull request, #4448:
URL: https://github.com/apache/fluss/pull/4448

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Re: [PR] [client][metrics] Expose record accumulator memory usage metrics. [fluss]

Posted by "platinumhamburg (via GitHub)" <gi...@apache.org>.

platinumhamburg commented on code in PR #4448:
URL: https://github.com/apache/fluss/pull/4448#discussion_r4058955121


##########
fluss-common/src/main/java/org/apache/fluss/metrics/MetricNames.java:
##########
@@ -339,6 +337,12 @@ public class MetricNames {
     public static final String WRITER_RECORDS_PER_BATCH = "recordsPerBatch";
     public static final String WRITER_SEND_LATENCY_MS = "sendLatencyMs";
 
+    // for record accumulator memory
+    public static final String WRITER_ACCUMULATOR_HEAP_MEMORY_USED = "accumulatorHeapMemoryUsed";
+    public static final String WRITER_ACCUMULATOR_ARROW_MEMORY_USED = "accumulatorArrowMemoryUsed";
+    public static final String WRITER_ACCUMULATOR_NATIVE_MEMORY_ALLOCATED =
+            "accumulatorNativeMemoryAllocated";

Review Comment:
   The existing writer metrics use explicit Bytes suffix (bufferTotalBytes, bufferAvailableBytes), and other metrics follow the same convention (bytesIn, rocksdbBytesReadTotal, replicationBytesInPerSecond, etc.). These three new metrics have no unit indicator.
   Suggest renaming to:
   ```
   accumulatorHeapMemoryUsedBytes
   accumulatorArrowMemoryUsedBytes
   accumulatorNativeMemoryAllocatedBytes
   ```



##########
fluss-common/src/main/java/org/apache/fluss/shaded/arrow/org/apache/arrow/memory/ChunkedAllocationManager.java:
##########
@@ -403,12 +420,31 @@ public synchronized void close() {
             closed = true;
             while (!freeChunks.isEmpty()) {
                 Chunk poll = freeChunks.poll();
-                poll.destroy();
-            }
-            if (activeChunk != null && activeChunk.subAllocCount.get() == 0) {
-                activeChunk.destroy();
+                destroyChunk(poll);
             }
+            Chunk chunk = activeChunk;
             activeChunk = null;
+            if (chunk != null && chunk.subAllocCount.get() == 0) {
+                // Invalidate a pending onChunkDrained callback that observed this zero count before
+                // close acquired the factory lock.
+                chunk.drainGeneration++;
+                destroyChunk(chunk);
+            }
+        }
+
+        /** Returns the native memory, in bytes, currently allocated by this factory. */
+        public long getNativeMemorySize() {
+            return nativeMemorySize.get();
+        }
+
+        private void destroyChunk(Chunk chunk) {
+            chunk.destroy();

Review Comment:
   nit: chunk.destroy() frees native memory via freeMemory(address), so reading chunk.capacity (a final long on the heap) after it is safe today. But if destroy() ever gains additional logic (e.g., nulling fields, callbacks), this ordering would silently break accounting.
   Suggest capturing before freeing:
   ```
   private void destroyChunk(Chunk chunk) {
       long cap = chunk.capacity;
       chunk.destroy();
       nativeMemorySize.addAndGet(-cap);
   }
   ```



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