Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/7839#discussion_r36354984
--- Diff:
network/yarn/src/main/java/org/apache/spark/network/yarn/YarnShuffleService.java
---
@@ -100,11 +121,34 @@ private boolean isAuthenticationEnabled() {
*/
@Override
protected void serviceInit(Configuration conf) {
+
+ // In case this NM was killed while there were running spark
applications, we need to restore
+ // lost state for the existing executors. We look for an existing
file in the NM's local dirs.
+ // If we don't find one, then we choose a file to use to save the
state next time. However, we
+ // do *not* immediately register all the executors in that file, just
in case the application
+ // was terminated while the NM was restarting. We wait until yarn
tells the service about the
+ // app again via #initializeApplication, so we know it's still
running. That is important
+ // for preventing a leak where the app data would stick around
*forever*. This does leave
+ // a small race -- if the NM restarts *again*, after only some of the
existing apps have been
--- End diff --
Sorry if I missed, but I don't remember seeing a reply about why is it ok
to introduce this race instead of relying on YARN behaving correctly? e.g.
always re-register everything and use `stopApplication` to clean things up.
You could also clean up the file in `serviceStop()` (depending on what the
semantics for that method are).
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