Allow AbstractQueueVisitor implementations to introspect on active worker count and possibly use that value to make dynamic decisions around scheduling.

--
MOS_MIGRATED_REVID=116351222

1 files changed, 17 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/concurrent/AbstractQueueVisitor.java b/src/main/java/com/google/devtools/build/lib/concurrent/AbstractQueueVisitor.java
index 3b7adf6946..22a16e1c27 100644
--- a/src/main/java/com/google/devtools/build/lib/concurrent/AbstractQueueVisitor.java
+++ b/src/main/java/com/google/devtools/build/lib/concurrent/AbstractQueueVisitor.java
@@ -409,7 +409,7 @@ public class AbstractQueueVisitor implements QuiescingExecutor {
   /** Schedules a call. Called in a worker thread if concurrent. */
   @Override
   public final void execute(Runnable runnable) {
-    if (concurrent) {
+    if (runConcurrently()) {
       WrappedRunnable wrappedRunnable = new WrappedRunnable(runnable);
       try {
         // It's impossible for this increment to result in remainingTasks.get <= 0 because
@@ -434,6 +434,22 @@ public class AbstractQueueVisitor implements QuiescingExecutor {
     }
   }
 
+  /**
+   * Subclasses may override this to make dynamic decisiouns about whether to run tasks
+   * asynchronously versus in-thread.
+   */
+  protected boolean runConcurrently() {
+    return concurrent;
+  }
+
+  /**
+   * Returns an approximate count of how many threads in the queue visitor's thread pool are
+   * occupied with tasks.
+   */
+  protected final int activeParallelTasks() {
+    return jobs.asMap().size();
+  }
+
   protected void executeRunnable(Runnable runnable) {
     executorService.execute(runnable);
   }