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

### What changes were proposed in this pull request?

This PR aims to support `On-Demand Log Loading` in `History Server` by looking up the **rolling event log locations** even Spark listing didn't finish to load the event log files.

```scala
val EVENT_LOG_ROLLING_ON_DEMAND_LOAD_ENABLED =
  ConfigBuilder("spark.history.fs.eventLog.rolling.onDemandLoadEnabled")
    .doc("Whether to look up rolling event log locations on demand manner before listing files.")
    .version("4.1.0")
    .booleanConf
    .createWithDefault(true)
```

Previously, Spark History Server will show `Application ... Not Found` page if a job is requested before scanning it even if the file exists in the correct location. So, this PR doesn't introduce any regressions because this aims to introduce a kind of fallback logic to improve error handling .

<img width="686" height="359" alt="Screenshot 2025-07-22 at 14 08 21" src="https://github.com/user-attachments/assets/fccb413c-5a57-4918-86c0-28ae81d54873" />

### Why are the changes needed?

Since Apache Spark 3.0, we have been using event log rolling not only for **long-running jobs**, but also for **some failed jobs** to archive the partial event logs incrementally.
- #25670

Since Apache Spark 4.0, event log rolling is enabled by default.
- #43638

On top of that, this PR aims to reduce storage cost at Apache Spark 4.1. By supporting `On-Demand Loading for rolled event logs`, we can use larger values for `spark.history.fs.update.interval` instead of the default `10s`. Although Spark History logs are consumed in various ways, It has a big benefit because most of successful Spark jobs's logs are not visited by the users.

### Does this PR introduce _any_ user-facing change?

No. This is a new feature.

### How was this patch tested?

Pass the CIs with newly added test case.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #51604 from dongjoon-hyun/SPARK-52914.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala

@@ -321,9 +321,13 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
   override def getLastUpdatedTime(): Long = lastScanTime.get()
 
   override def getAppUI(appId: String, attemptId: Option[String]): Option[LoadedAppUI] = {
+    val logPath = RollingEventLogFilesWriter.EVENT_LOG_DIR_NAME_PREFIX +
+        EventLogFileWriter.nameForAppAndAttempt(appId, attemptId)
     val app = try {
       load(appId)
      } catch {
+      case _: NoSuchElementException if this.conf.get(EVENT_LOG_ROLLING_ON_DEMAND_LOAD_ENABLED) =>
+        loadFromFallbackLocation(appId, attemptId, logPath)
       case _: NoSuchElementException =>
         return None
     }
@@ -345,6 +349,13 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
           createInMemoryStore(attempt)
       }
     } catch {
+      case _: FileNotFoundException if this.conf.get(EVENT_LOG_ROLLING_ON_DEMAND_LOAD_ENABLED) =>
+        if (app.attempts.head.info.appSparkVersion == "unknown") {
+          listing.synchronized {
+            listing.delete(classOf[ApplicationInfoWrapper], appId)
+          }
+        }
+        return None
       case _: FileNotFoundException =>
         return None
     }
@@ -364,6 +375,18 @@ 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 lastUpdate = new Date()
+    val info = ApplicationAttemptInfo(
+      attemptId, date, date, lastUpdate, 0, "spark", false, "unknown")
+    addListing(new ApplicationInfoWrapper(
+      ApplicationInfo(appId, appId, None, None, None, None, List.empty),
+      List(new AttemptInfoWrapper(info, logPath, 0, Some(1), None, None, None, None))))
+    load(appId)
+  }
+
   override def getEmptyListingHtml(): Seq[Node] = {
     <p>
       Did you specify the correct logging directory? Please verify your setting of

core/src/main/scala/org/apache/spark/internal/config/History.scala

@@ -159,6 +159,13 @@ private[spark] object History {
       .doubleConf
       .createWithDefault(0.7d)
 
+  val EVENT_LOG_ROLLING_ON_DEMAND_LOAD_ENABLED =
+    ConfigBuilder("spark.history.fs.eventLog.rolling.onDemandLoadEnabled")
+      .doc("Whether to look up rolling event log locations on demand manner before listing files.")
+      .version("4.1.0")
+      .booleanConf
+      .createWithDefault(true)
+
   val DRIVER_LOG_CLEANER_ENABLED = ConfigBuilder("spark.history.fs.driverlog.cleaner.enabled")
     .version("3.0.0")
     .doc("Specifies whether the History Server should periodically clean up driver logs from " +

core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala

@@ -1640,6 +1640,40 @@ abstract class FsHistoryProviderSuite extends SparkFunSuite with Matchers with P
     }
   }
 
+  test("SPARK-52914: Support spark.history.fs.eventLog.rolling.onDemandLoadEnabled") {
+    Seq(true, false).foreach { onDemandEnabled =>
+      withTempDir { dir =>
+        val conf = createTestConf(true)
+        conf.set(HISTORY_LOG_DIR, dir.getAbsolutePath)
+        conf.set(EVENT_LOG_ROLLING_ON_DEMAND_LOAD_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(dir.listFiles().length === 1)
+        assert(provider.getListing().length === 0)
+        assert(provider.getAppUI("app1", None).isDefined == onDemandEnabled)
+        assert(provider.getListing().length === (if (onDemandEnabled) 1 else 0))
+
+        // The dummy entry should be protected from cleanLogs()
+        provider.cleanLogs()
+        assert(dir.listFiles().length === 1)
+
+        assert(dir.listFiles().length === 1)
+        assert(provider.getAppUI("nonexist", None).isEmpty)
+        assert(provider.getListing().length === (if (onDemandEnabled) 1 else 0))
+
+        provider.stop()
+      }
+    }
+  }
+
   test("SPARK-36354: EventLogFileReader should skip rolling event log directories with no logs") {
     withTempDir { dir =>
       val conf = createTestConf(true)