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[SPARK-52914][CORE] Support On-Demand Log Loading for rolling logs in History Server #51604

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[SPARK-52914][CORE] Support On-Demand Log Loading for rolling logs in History Server #51604

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[SPARK-52914][CORE] Support `On-Demand Log Loading` in `History Server`
dongjoon-hyun Jul 21, 2025
ef9b833
Address comments
dongjoon-hyun Jul 22, 2025
db5773b
Revise test case name
dongjoon-hyun Jul 22, 2025
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dongjoon-hyun Jul 23, 2025
4ee04af
Update core/src/main/scala/org/apache/spark/deploy/history/FsHistoryP…
dongjoon-hyun Jul 23, 2025
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14 changes: 14 additions & 0 deletions core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -324,6 +324,10 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
val app = try {
load(appId)
} catch {
case _: NoSuchElementException if this.conf.get(ON_DEMAND_ENABLED) =>
val name = Utils.nameForAppAndAttempt(appId, attemptId)
loadFromFallbackLocation(appId, attemptId,
RollingEventLogFilesWriter.EVENT_LOG_DIR_NAME_PREFIX + name)
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@mridulm mridulm Jul 22, 2025 •
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We should not assume it will be RollingEventLogFilesWriter, users dont need to be running with the default enabled, right ?

case _: NoSuchElementException =>
return None
}
Expand Down Expand Up @@ -364,6 +368,16 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
Some(loadedUI)
}

private def loadFromFallbackLocation(appId: String, attemptId: Option[String], logPath: String)
: ApplicationInfoWrapper = {
val date = new Date(0)
val info = ApplicationAttemptInfo(attemptId, date, date, date, 0, "spark", false, "unknown")
addListing(new ApplicationInfoWrapper(
ApplicationInfo(appId, appId, None, None, None, None, List.empty),
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@viirya viirya Jul 23, 2025

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So supposedly, the appId should be correct to load the record, but other info are dummy?

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@viirya viirya Jul 23, 2025

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And once periodic scanning happens, it will update the record with correct information?

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@dongjoon-hyun dongjoon-hyun Jul 23, 2025

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Yes, correct, @viirya ~

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@dongjoon-hyun dongjoon-hyun Jul 23, 2025

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This is a kind of placeholder.

List(new AttemptInfoWrapper(info, logPath, 0, Some(1), None, None, None, None))))
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@thejdeep thejdeep Jul 22, 2025

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Shouldn't we rely on the event log for information like startTime, endTime, user etc ? Will this not lead to incorrect information being displayed on the home page of SHS ?

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@dongjoon-hyun dongjoon-hyun Jul 22, 2025

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This is only a dummy place to allow SHS shows the application logs before periodic scanning happens. The periodic scanning will keep it in sync.

BTW, I'm wondering how many times do you think this fallback is used in the production environments, @thejdeep ? I'm curious if you are thinking about turning off the periodic scanning.

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@thejdeep thejdeep Jul 22, 2025

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Oh I see that the intention is just to have dummy placeholders until the scanning takes care of it.

If users operate with a large Spark cluster, my two cents are that users may tend to access their app on demand much more frequently and it might just lead to a incorrect listing page. For example, we noticed that a good fraction of our SHS requests are on demand since users would like to get their reports as soon as their app finishes and before checkForLogs completes.

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@dongjoon-hyun dongjoon-hyun Jul 22, 2025 •
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Yes, and technically, it's not exposed in the listing page. Could you build this PR and test it by yourself?

a incorrect listing page

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@dongjoon-hyun dongjoon-hyun Jul 22, 2025 •
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It sounds like a limitation of a single file event log, @thejdeep . If you have rolling event logs, SHS have the correct partial information already while your jobs are running.

For example, we noticed that a good fraction of our SHS requests are on demand since users would like to get their reports as soon as their app finishes and before checkForLogs completes.

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@dongjoon-hyun dongjoon-hyun Jul 22, 2025 •
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Just questions to understand your use cases:

  • How do you handle Spark Streaming Jobs with a single file event log ? Still your job doesn't use rolling event logs?
  • Are you assuming only Spark 2.x or 3.x jobs because Spark 4 jobs generates rolling events by default since SPARK-45771?

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@thejdeep thejdeep Jul 22, 2025

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Thanks for sharing context @dongjoon-hyun .

We currently do not use rolling event logs since we only currently serve batch use-cases. All applications are currently on 3.x.

I can build your PR locally and test it on single file event logs to see how it works with listing and cleanup. I can get back to you earliest by tomorrow if that works.

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@dongjoon-hyun dongjoon-hyun Jul 22, 2025 •
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Thank you so much for the info and your efforts on reviewing this. Take your time.

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@thejdeep thejdeep Jul 22, 2025

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@dongjoon-hyun wanted to get your thoughts on #51604 (comment)

Thank you!

load(appId)
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@mridulm mridulm Jul 22, 2025

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What is the behavior if the application does not exist ? (typo in user query for example)
Will the listing now have an invalid entry ?

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@thejdeep thejdeep Jul 22, 2025

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+1, do you think it will be better if we check for the existence of the file at its location before adding an entry ? This is to keep parity with how checkForLogs works - we only add entries for whose event log locations exist.

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@dongjoon-hyun dongjoon-hyun Jul 22, 2025

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No, we had better avoid that because it requires the full path including "s3://...", @thejdeep .

}

override def getEmptyListingHtml(): Seq[Node] = {
<p>
Did you specify the correct logging directory? Please verify your setting of
Expand Down
6 changes: 6 additions & 0 deletions core/src/main/scala/org/apache/spark/internal/config/History.scala
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Expand Up @@ -54,6 +54,12 @@ private[spark] object History {
.checkValue(v => v > 0, "The update batchSize should be a positive integer.")
.createWithDefault(Int.MaxValue)

val ON_DEMAND_ENABLED = ConfigBuilder("spark.history.fs.update.onDemandEnabled")
.version("4.1.0")
.doc("Whether to look up rolling event log locations on demand manner before listing files.")
.booleanConf
.createWithDefault(true)

val CLEANER_ENABLED = ConfigBuilder("spark.history.fs.cleaner.enabled")
.version("1.4.0")
.doc("Whether the History Server should periodically clean up event logs from storage")
Expand Down
25 changes: 25 additions & 0 deletions core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala
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Expand Up @@ -1640,6 +1640,31 @@ abstract class FsHistoryProviderSuite extends SparkFunSuite with Matchers with P
}
}

test("SPARK-52914: Support spark.history.fs.update.onDemandEnabled") {
Seq(true, false).foreach { onDemandEnabled =>
withTempDir { dir =>
val conf = createTestConf(true)
conf.set(HISTORY_LOG_DIR, dir.getAbsolutePath)
conf.set(ON_DEMAND_ENABLED, onDemandEnabled)
val hadoopConf = SparkHadoopUtil.newConfiguration(conf)
val provider = new FsHistoryProvider(conf)

val writer1 = new RollingEventLogFilesWriter("app1", None, dir.toURI, conf, hadoopConf)
writer1.start()
writeEventsToRollingWriter(writer1, Seq(
SparkListenerApplicationStart("app1", Some("app1"), 0, "user", None),
SparkListenerJobStart(1, 0, Seq.empty)), rollFile = false)
writer1.stop()

assert(provider.getListing().length === 0)
assert(dir.listFiles().length === 1)
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@dongjoon-hyun dongjoon-hyun Jul 23, 2025

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This is the test coverage, @thejdeep .

assert(provider.getAppUI("app1", None).isDefined == onDemandEnabled)

provider.stop()
}
}
}

test("SPARK-36354: EventLogFileReader should skip rolling event log directories with no logs") {
withTempDir { dir =>
val conf = createTestConf(true)
Expand Down