Make it possible to set the CentralJobScheduler top-level group name.

And have the causal cluster code use this to publish and tag their cluster member identities to their threads.

community/common/src/main/java/org/neo4j/scheduler/JobScheduler.java

@@ -255,6 +255,14 @@ interface CancelListener
         void cancelled( boolean mayInterruptIfRunning );
     }
 
+    /**
+     * Assign a specific name to the top-most scheduler group.
+     * <p>
+     * This is just a suggestion for debugging purpose. The specific scheduler implementation is free to ignore calls
+     * to this method.
+     */
+    void setTopLevelGroupName( String name );
+
     /** Expose a group scheduler as an {@link Executor} */
     Executor executor( Group group );
 

community/common/src/test/java/org/neo4j/scheduler/JobSchedulerAdapter.java

@@ -46,6 +46,11 @@ public void shutdown()
     {   // no-op
     }
 
+    @Override
+    public void setTopLevelGroupName( String name )
+    {
+    }
+
     @Override
     public Executor executor( Group group )
     {

community/kernel/src/main/java/org/neo4j/kernel/impl/scheduler/CentralJobScheduler.java

@@ -19,6 +19,7 @@
  */
 package org.neo4j.kernel.impl.scheduler;
 
+import java.lang.reflect.Field;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
@@ -47,15 +48,30 @@ public class CentralJobScheduler extends LifecycleAdapter implements JobSchedule
     // fashion.
     private final ConcurrentHashMap<Group,ExecutorService> workStealingExecutors;
 
-    private final ThreadGroup topLevelGroup;
+    private final TopLevelGroup topLevelGroup;
     private final ThreadPoolManager pools;
 
     private volatile boolean started;
 
+    private static class TopLevelGroup extends ThreadGroup
+    {
+        TopLevelGroup()
+        {
+            super ( "Neo4j-" + INSTANCE_COUNTER.incrementAndGet() );
+        }
+
+        public void setName( String name ) throws Exception
+        {
+            Field field = ThreadGroup.class.getDeclaredField( "name" );
+            field.setAccessible( true );
+            field.set( this, name );
+        }
+    }
+
     public CentralJobScheduler()
     {
         workStealingExecutors = new ConcurrentHashMap<>( 1 );
-        topLevelGroup = new ThreadGroup( "Neo4j-" + INSTANCE_COUNTER.incrementAndGet() );
+        topLevelGroup = new TopLevelGroup();
         pools = new ThreadPoolManager( topLevelGroup );
         ThreadFactory threadFactory = new GroupedDaemonThreadFactory( SCHEDULER_GROUP, topLevelGroup );
         scheduler = new TimeBasedTaskScheduler( Clocks.nanoClock(), pools );
@@ -66,6 +82,18 @@ public CentralJobScheduler()
         schedulerThread.setPriority( priority );
     }
 
+    @Override
+    public void setTopLevelGroupName( String name )
+    {
+        try
+        {
+            topLevelGroup.setName( name );
+        }
+        catch ( Exception ignore )
+        {
+        }
+    }
+
     @Override
     public void init()
     {

community/kernel/src/main/java/org/neo4j/kernel/impl/scheduler/GroupedDaemonThreadFactory.java

@@ -40,7 +40,23 @@ final class GroupedDaemonThreadFactory implements ThreadFactory, ForkJoinPool.Fo
     @Override
     public Thread newThread( @SuppressWarnings( "NullableProblems" ) Runnable job )
     {
-        Thread thread = new Thread( threadGroup, job, group.threadName() );
+        Thread thread = new Thread( threadGroup, job, group.threadName() )
+        {
+            @Override
+            public String toString()
+            {
+                StringBuilder sb = new StringBuilder( "Thread[" ).append( getName() );
+                ThreadGroup group = getThreadGroup();
+                String sep = ", in ";
+                while ( group != null )
+                {
+                    sb.append( sep ).append( group.getName() );
+                    group = group.getParent();
+                    sep = "/";
+                }
+                return sb.append( ']' ).toString();
+            }
+        };
         thread.setDaemon( true );
         return thread;
     }

community/kernel/src/test/java/org/neo4j/kernel/impl/util/CountingJobScheduler.java

@@ -39,6 +39,12 @@ public CountingJobScheduler( AtomicInteger counter, CentralJobScheduler delegate
         this.delegate = delegate;
     }
 
+    @Override
+    public void setTopLevelGroupName( String name )
+    {
+        delegate.setTopLevelGroupName( name );
+    }
+
     @Override
     public Executor executor( Group group )
     {

community/kernel/src/test/java/org/neo4j/test/FakeClockJobScheduler.java

@@ -88,6 +88,11 @@ private long now()
         return instant().toEpochMilli();
     }
 
+    @Override
+    public void setTopLevelGroupName( String name )
+    {
+    }
+
     @Override
     public Executor executor( Group group )
     {

community/kernel/src/test/java/org/neo4j/test/OnDemandJobScheduler.java

@@ -20,7 +20,6 @@
 package org.neo4j.test;
 
 import java.util.List;
-import java.util.Map;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
@@ -46,6 +45,11 @@ public OnDemandJobScheduler( boolean removeJobsAfterExecution )
         this.removeJobsAfterExecution = removeJobsAfterExecution;
     }
 
+    @Override
+    public void setTopLevelGroupName( String name )
+    {
+    }
+
     @Override
     public Executor executor( Group group )
     {

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/core/IdentityModule.java

@@ -70,6 +70,8 @@ public class IdentityModule
         {
             throw new RuntimeException( e );
         }
+
+        platformModule.jobScheduler.setTopLevelGroupName( "Core " + myself );
     }
 
     public MemberId myself()

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/readreplica/EnterpriseReadReplicaEditionModule.java

@@ -152,6 +152,7 @@ public EnterpriseReadReplicaEditionModule( final PlatformModule platformModule,
         LogService logging = platformModule.logging;
 
         ioLimiter = new ConfigurableIOLimiter( platformModule.config );
+        platformModule.jobScheduler.setTopLevelGroupName( "ReadReplica " + myself );
 
         org.neo4j.kernel.impl.util.Dependencies dependencies = platformModule.dependencies;
         Config config = platformModule.config;

integrationtests/src/test/java/org/neo4j/auth/FlatFileStressBase.java

@@ -164,6 +164,11 @@ void setActions( Runnable... actions )
 
     private class NoopJobScheduler extends LifecycleAdapter implements JobScheduler
     {
+        @Override
+        public void setTopLevelGroupName( String name )
+        {
+        }
+
         @Override
         public Executor executor( Group group )
         {