Index: oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStats.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStats.java	(revision 9795521f6f8ec6869287f1c55458505a2ec68844)
+++ oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStats.java	(date 1529465785000)
@@ -22,6 +22,7 @@
 
 import org.apache.jackrabbit.api.stats.TimeSeries;
 import org.apache.jackrabbit.oak.plugins.document.VersionGarbageCollector.VersionGCStats;
+import org.apache.jackrabbit.oak.stats.CounterStats;
 import org.apache.jackrabbit.oak.stats.MeterStats;
 import org.apache.jackrabbit.oak.stats.StatisticsProvider;
 import org.apache.jackrabbit.oak.stats.TimerStats;
@@ -35,7 +36,6 @@
  * DocumentNodeStore revision garbage collection statistics.
  */
 class RevisionGCStats implements RevisionGCStatsCollector, RevisionGCStatsMBean {
-
     static final String RGC = "RevisionGC";
     static final String READ_DOC = "READ_DOC";
     static final String DELETE_DOC = "DELETE_DOC";
@@ -52,6 +52,9 @@
     static final String DELETE_DOC_TIMER = "DELETE_DOC_TIMER";
     static final String DELETE_SPLIT_DOC_TIMER = "DELETE_SPLIT_DOC_TIMER";
 
+    static final String START_COUNTER = "START";
+    static final String FINISH_FAILURE_COUNTER = "FINISH_FAILURE";
+
     private final StatisticsProvider provider;
 
     private final MeterStats readDoc;
@@ -69,6 +72,9 @@
     private final TimerStats deletedDocTimer;
     private final TimerStats deletedSplitDocTimer;
 
+    private final CounterStats startCounter;
+    private final CounterStats finishFailureCounter;
+
     RevisionGCStats(StatisticsProvider provider) {
         this.provider = provider;
 
@@ -86,6 +92,9 @@
         resetDeletedFlagTimer = timer(provider, RESET_DELETED_FLAG_TIMER);
         deletedDocTimer = timer(provider, DELETE_DOC_TIMER);
         deletedSplitDocTimer = timer(provider, DELETE_SPLIT_DOC_TIMER);
+
+        startCounter = counter(provider, START_COUNTER);
+        finishFailureCounter = counter(provider, FINISH_FAILURE_COUNTER);
     }
 
     //---------------------< RevisionGCStatsCollector >-------------------------
@@ -124,6 +133,11 @@
         resetDeletedFlag.mark();
     }
 
+    @Override
+    public void start() {
+        startCounter.inc();
+    }
+
     @Override
     public void finished(VersionGCStats stats) {
         activeTimer.update(stats.active.elapsed(MICROSECONDS), MICROSECONDS);
@@ -135,6 +149,10 @@
         resetDeletedFlagTimer.update(stats.updateResurrectedDocumentsElapsed, MICROSECONDS);
     }
 
+    @Override
+    public void finishedFailure() {
+        finishFailureCounter.inc();
+    }
 
     //------------------------< RevisionGCStatsMBean >--------------------------
 
@@ -217,6 +235,11 @@
         return provider.getTimer(qualifiedName(name), METRICS_ONLY);
     }
 
+    private static CounterStats counter(StatisticsProvider provider,
+                                        String name) {
+        return provider.getCounterStats(qualifiedName(name), METRICS_ONLY);
+    }
+
     private static String qualifiedName(String metricName) {
         return RGC + "." + metricName;
     }
Index: oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStatsCollector.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStatsCollector.java	(revision 9795521f6f8ec6869287f1c55458505a2ec68844)
+++ oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStatsCollector.java	(date 1529388219000)
@@ -38,5 +38,9 @@
 
     void deletedOnceFlagReset();
 
+    void start();
+
     void finished(VersionGCStats stats);
-}
\ No newline at end of file
+
+    void finishedFailure();
+}
Index: oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/VersionGarbageCollector.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/VersionGarbageCollector.java	(revision 9795521f6f8ec6869287f1c55458505a2ec68844)
+++ oak-store-document/src/main/java/org/apache/jackrabbit/oak/plugins/document/VersionGarbageCollector.java	(date 1529388576000)
@@ -135,6 +135,8 @@
         if (collector.compareAndSet(null, job)) {
             VersionGCStats overall = new VersionGCStats();
             overall.active.start();
+            gcStats.start();
+            boolean thrown = true;
             try {
                 long averageDurationMs = 0;
                 while (maxRunTime.contains(nodeStore.getClock().getTime() + averageDurationMs)) {
@@ -152,10 +154,15 @@
                     averageDurationMs = ((averageDurationMs * (overall.iterationCount - 1))
                             + stats.active.elapsed(TimeUnit.MILLISECONDS)) / overall.iterationCount;
                 }
+
+                thrown = false;
                 gcStats.finished(overall);
                 return overall;
             } finally {
                 overall.active.stop();
+                if (thrown) {
+                    gcStats.finishedFailure();
+                }
                 collector.set(null);
                 if (overall.iterationCount > 1) {
                     gcMonitor.info("Revision garbage collection finished after {} iterations - aggregate statistics: {}",
Index: oak-store-document/src/test/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStatsTest.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-store-document/src/test/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStatsTest.java	(revision 9795521f6f8ec6869287f1c55458505a2ec68844)
+++ oak-store-document/src/test/java/org/apache/jackrabbit/oak/plugins/document/RevisionGCStatsTest.java	(date 1529465796000)
@@ -20,6 +20,7 @@
 
 import java.util.concurrent.ScheduledExecutorService;
 
+import com.codahale.metrics.Counter;
 import com.codahale.metrics.Meter;
 import com.codahale.metrics.Timer;
 
@@ -130,6 +131,22 @@
         assertTimer(13, RevisionGCStats.RESET_DELETED_FLAG_TIMER);
     }
 
+    @Test
+    public void counters() {
+        Counter startCounter = getCounter(RevisionGCStats.START_COUNTER);
+        Counter finishFailureCounter = getCounter(RevisionGCStats.FINISH_FAILURE_COUNTER);
+
+        stats.start();
+        assertEquals(1, startCounter.getCount());
+
+        VersionGCStats vgcs = new VersionGCStats();
+        stats.finished(vgcs);
+        assertEquals(0, finishFailureCounter.getCount());
+
+        stats.finishedFailure();
+        assertEquals(1, finishFailureCounter.getCount());
+    }
+
     private void assertTimer(long expected, String name) {
         assertEquals(expected, NANOSECONDS.toMillis(getTimer(name).getSnapshot().getMax()));
     }
@@ -141,4 +158,9 @@
     private Meter getMeter(String name) {
         return statsProvider.getRegistry().getMeters().get(RGC + "." + name);
     }
+
+    private Counter getCounter(String name) {
+        return statsProvider.getRegistry().getCounters().get(RGC + "." + name);
+    }
+
 }