Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/11118#discussion_r52614670
--- Diff:
core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala ---
@@ -511,6 +545,14 @@ private[history] class FsHistoryProvider(conf:
SparkConf, clock: Clock)
bus: ReplayListenerBus): Option[FsApplicationAttemptInfo] = {
val logPath = eventLog.getPath()
logInfo(s"Replaying log path: $logPath")
+ // Note that the eventLog may have *increased* in size since when we
grabbed the filestatus,
+ // and when we read the file here. That is OK -- it may result in an
unnecessary refresh
+ // when there is no update, but will not result in missing an update.
We *must* prevent
+ // an error the other way -- if we report a size bigger (ie later)
than the file that is
+ // actually read, we may never refresh the app
+ // we expect FileStatus to return the file size when it was initially
created, but the api
+ // is not explicit about this so lets be extra-safe.
+ val eventLogLength = eventLog.getLen()
--- End diff --
ah I see, I expected it to behave that way but couldn't find any
documentation which really made that explicit. I guess you're saying its
guaranteed by the post-conditions for getFileStatus()? I've updated the
comment now.
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