[FIX] Start jobs only once (II). #2543

Author: ChristianGruen

basex-core/src/main/java/org/basex/core/jobs/QueryJob.java

@@ -5,6 +5,7 @@
 
 import java.util.*;
 import java.util.Map.*;
+import java.util.concurrent.atomic.*;
 import java.util.function.*;
 
 import org.basex.core.*;
@@ -34,7 +35,7 @@ public final class QueryJob extends Job implements Runnable {
   /** Remove flag. */
   private boolean remove;
   /** Running flag. */
-  private boolean running;
+  private final AtomicBoolean running = new AtomicBoolean(false);
 
   /**
    * Constructor, which creates and registers the specified job.
@@ -98,7 +99,7 @@ public QueryJob(final QueryJobSpec job, final Context context, final InputInfo i
       }
 
       // create and schedule job task
-      final QueryJobTask task = new QueryJobTask(this, jobs, delay, interval, duration);
+      final QueryJobTask task = new QueryJobTask(this, delay, interval, duration);
       jobs.tasks.put(id, task);
       if(interval > 0) {
         jobs.timer.scheduleAtFixedRate(task, delay, interval);
@@ -176,16 +177,14 @@ void remove() {
   }
 
   /**
-   * Indicates if the job is currently running.
-   * @return result of check
+   * Starts the job if it is not currently running.
    */
-  boolean running() {
-    return running;
+  void startIfNotRunning() {
+    if(running.compareAndSet(false, true)) new Thread(this).start();
   }
 
   @Override
   public void run() {
-    running = true;
     try {
       result.init();
 
@@ -265,7 +264,7 @@ public void run() {
         if(result.value != null && result.value.isEmpty()) ctx.jobs.results.remove(id);
       }
     } finally {
-      running = false;
+      running.set(false);
     }
   }
 

basex-core/src/main/java/org/basex/core/jobs/QueryJobTask.java

@@ -13,8 +13,6 @@
 public final class QueryJobTask extends TimerTask {
   /** Job. */
   public final QueryJob job;
-  /** Job pool. */
-  public final JobPool jobs;
   /** Interval. */
   public final long interval;
   /** End time (@link {@link Long#MAX_VALUE}: no end). */
@@ -26,16 +24,13 @@ public final class QueryJobTask extends TimerTask {
   /**
    * Constructor.
    * @param job job
-   * @param jobs job pool
    * @param delay delay (ms)
    * @param interval interval (ms; no repetition: {@code 0})
    * @param duration total duration (ms; no limit: {@link Long#MAX_VALUE})
    */
-  public QueryJobTask(final QueryJob job, final JobPool jobs, final long delay,
-      final long interval, final long duration) {
-
+  public QueryJobTask(final QueryJob job, final long delay, final long interval,
+      final long duration) {
     this.job = job;
-    this.jobs = jobs;
     this.interval = interval;
     final long time = System.currentTimeMillis();
     start = time + delay;
@@ -50,8 +45,7 @@ public void run() {
       job.remove();
       cancel();
     }
-    // skip execution if same job is still running
-    if(!job.running()) new Thread(job).start();
+    job.startIfNotRunning();
   }
 
   @Override