Run a GC every 30 minutes (configurable)

Author: Andrew Or

core/src/main/scala/org/apache/spark/ContextCleaner.scala

@@ -18,12 +18,13 @@
 package org.apache.spark
 
 import java.lang.ref.{ReferenceQueue, WeakReference}
+import java.util.concurrent.{TimeUnit, ScheduledExecutorService}
 
 import scala.collection.mutable.{ArrayBuffer, SynchronizedBuffer}
 
 import org.apache.spark.broadcast.Broadcast
 import org.apache.spark.rdd.{RDD, ReliableRDDCheckpointData}
-import org.apache.spark.util.Utils
+import org.apache.spark.util.{ThreadUtils, Utils}
 
 /**
  * Classes that represent cleaning tasks.
@@ -66,6 +67,20 @@ private[spark] class ContextCleaner(sc: SparkContext) extends Logging {
 
   private val cleaningThread = new Thread() { override def run() { keepCleaning() }}
 
+  private val periodicGCService: ScheduledExecutorService =
+    ThreadUtils.newDaemonSingleThreadScheduledExecutor("context-cleaner-periodic-gc")
+
+  /**
+   * How often to trigger a garbage collection in this JVM.
+   *
+   * This context cleaner triggers cleanups only when weak references are garbage collected.
+   * In long-running applications with large driver JVMs, where there is little memory pressure
+   * on the driver, this may happen very occasionally or not at all. Not cleaning at all may
+   * lead to executors running out of disk space after a while.
+   */
+  private val periodicGCInterval =
+    sc.conf.getTimeAsSeconds("spark.cleaner.periodicGC.interval", "30min")
+
   /**
    * Whether the cleaning thread will block on cleanup tasks (other than shuffle, which
    * is controlled by the `spark.cleaner.referenceTracking.blocking.shuffle` parameter).
@@ -104,6 +119,9 @@ private[spark] class ContextCleaner(sc: SparkContext) extends Logging {
     cleaningThread.setDaemon(true)
     cleaningThread.setName("Spark Context Cleaner")
     cleaningThread.start()
+    periodicGCService.scheduleAtFixedRate(new Runnable {
+      override def run(): Unit = System.gc()
+    }, periodicGCInterval, periodicGCInterval, TimeUnit.SECONDS)
   }
 
   /**
@@ -119,6 +137,7 @@ private[spark] class ContextCleaner(sc: SparkContext) extends Logging {
       cleaningThread.interrupt()
     }
     cleaningThread.join()
+    periodicGCService.shutdown()
   }
 
   /** Register a RDD for cleanup when it is garbage collected. */