smengcl commented on code in PR #10988:
URL: https://github.com/apache/ozone/pull/10988#discussion_r3755382360
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hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/volume/MutableVolumeSet.java:
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@@ -404,6 +405,16 @@ public boolean hasEnoughVolumes() {
return hasEnoughVolumes;
}
+ /**
+ * Returns a consistent snapshot of the storage reports under the volume-set
+ * read lock.
+ *
+ * <p>Do not call this from metrics collection (or any caller that may hold
the
+ * {@code DefaultMetricsSystem} monitor): a volume-failure handler holds the
+ * volume-set write lock while unregistering volume metrics under that same
+ * monitor, so taking the read lock here can deadlock the metrics system. Use
+ * {@link #getStorageReportSnapshot()} from those paths instead.
+ */
public StorageLocationReport[] getStorageReport() {
this.readLock();
Review Comment:
The lock was added way back in HDDS-354 to fix NPE. Without the lock, you
get inconsistent view and hit NPE in `getNodeReport()` with the current impl.
Note: method was renamed from `getNodeReport()` to `getStorageReport()` in
HDDS-3807.
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