Re: [PR] fix: OrcInputFormat concurrent FileSystem init race condition (#19491) (druid)

["FrankChen021 (via GitHub)" <gi...@apache.org>]

FrankChen021 commented on code in PR #19497:
URL: https://github.com/apache/druid/pull/19497#discussion_r3281507046


##########
extensions-core/orc-extensions/src/main/java/org/apache/druid/data/input/orc/OrcInputFormat.java:
##########
@@ -55,14 +57,15 @@ public OrcInputFormat(
     this.conf = conf;
   }
 
-  private void initialize(Configuration conf)
+  // Ensure FileSystem class-level initialization happens with the correct classloader (see #1714).
+  // Called once on first createReader() via AtomicBoolean guard to prevent a race when multiple
+  // subtasks concurrently swap Thread.currentThread().setContextClassLoader() (see #19491).
+  private void ensureFileSystemInitialized()
   {
-    //Initializing seperately since during eager initialization, resolving
-    //namenode hostname throws an error if nodes are ephemeral
-
-    // Ensure that FileSystem class level initialization happens with correct CL
-    // See https://github.com/apache/druid/issues/1714
-    ClassLoader currCtxCl = Thread.currentThread().getContextClassLoader();
+    if (!fileSystemInitialized.compareAndSet(false, true)) {

Review Comment:
   [P2] Reset initialization guard when FileSystem init fails
   
   `compareAndSet(false, true)` marks the format initialized before `FileSystem.get(conf)` has actually succeeded. If that call throws an `IOException`, the flag remains true and every later `createReader` on the same `OrcInputFormat` skips the classloader-protected Hadoop FileSystem initialization instead of retrying, which is a regression from the previous per-reader behavior. Set the flag only after `FileSystem.get(conf)` succeeds, or reset it in the catch path before rethrowing.



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