[GitHub] [samza] jia-gao commented on a diff in pull request #1652: Fix deadlock in StreamAppender

["jia-gao (via GitHub)" <gi...@apache.org>]

jia-gao commented on code in PR #1652:
URL: https://github.com/apache/samza/pull/1652#discussion_r1092286850


##########
samza-log4j2/src/main/java/org/apache/samza/logging/log4j2/StreamAppender.java:
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@@ -186,13 +190,20 @@ public void append(LogEvent event) {
       if (!systemInitialized) {
         // configs are needed to set up producer system, so check that before actually initializing
         if (this.loggingContextHolder.getConfig() != null) {
-          synchronized (this) {
-            if (!systemInitialized) {
-              setupSystem();
-              systemInitialized = true;
+          if (setUpSystemLock.tryLock(SET_UP_SYSTEM_TIMEOUT_MILLI_SECONDS, TimeUnit.MILLISECONDS)) {
+            try {
+              if (!systemInitialized) {
+                setupSystem();

Review Comment:
   Yes, it is supposed to be run only once.
   I prefer not to set it to true within finally block because we want to make sure it is only set to true if setupSystem() is completed successfully. In case that setupSystem() fails (throwing some exceptions for example), we want to leave it as false.
   
   The same reason applies to the option of AtomicBoolean. there are two cons for that:
   1. same as above, can not make sure setupSystem() runs fine
   2. perf reason, compareAndSet AtomicBoolean in line 190 means every time LOG.xxx() StreamAppender needs to check the AtomicBoolean which is expensive than checking a boolean



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