Report ZGC individual collections instead of cycles (#445) (#447)

* Report ZGC individual collections instead of cycles

Previously, the ZGC parser would attempt to construct a single event for
each minor/major cycle, with each minor cycle containing a single young
collection, and each major cycle containing a single young and a single
old collection.

This created a few problems.

First, the implementation of the parser assumed that only one cycle could
be active at any given time. As a result, any time a minor cycle started
before the previous major cycle was finished, all data collected about the
major cycle would be lost.

Second, the data model for a MajorZGCCycle assumed there could be only one
young collection per cycle. This is not the case. There can be (and
frequently are) multiple young collections in a major cycle.

Even if the implementation and datamodel were fixed to account for the
concurrent nature of generational ZGC, grouping collections by cycle would
still create API usability problems. Individual collections within a cycle
independently report various JVM/heap level metrics at specific points in
time. Within a single major cycle, those points in time may be very far
apart, and overlap with a large number of minor cycles. If an end user
wished to construct a timeline for a particular metric (for example, heap
occupancy), they would need to traverse all the reported cycles, extract
the metrics from the individual collections, and put them in order.

To address the above issues, the parser and data models are refactored to
report each individual collection (young, old, or full) immediately once
they are completed instead of waiting until the parent cycle is done. The
parser maintains 3 independent forward references (one for each collection
type: old, young, and full). As a result, the parser will not lose state
even when lines from an old collection are intermixed with lines from a
young collection.

* Fix mismatched GC type label

* Rename ZGCCollectionType -> ZGCCycleType

* Fix inconsistent whitespace

* Use explicit imports in ZGCParserTest

Author: akiselev98

IT/src/main/java/com/microsoft/gctoolkit/integration/aggregation/CollectionCycleCountsAggregator.java

@@ -7,9 +7,9 @@
 import com.microsoft.gctoolkit.event.g1gc.G1GCPauseEvent;
 import com.microsoft.gctoolkit.event.generational.GenerationalGCPauseEvent;
 import com.microsoft.gctoolkit.event.shenandoah.ShenandoahCycle;
-import com.microsoft.gctoolkit.event.zgc.FullZGCCycle;
-import com.microsoft.gctoolkit.event.zgc.MajorZGCCycle;
-import com.microsoft.gctoolkit.event.zgc.MinorZGCCycle;
+import com.microsoft.gctoolkit.event.zgc.ZGCFullCollection;
+import com.microsoft.gctoolkit.event.zgc.ZGCYoungCollection;
+import com.microsoft.gctoolkit.event.zgc.ZGCOldCollection;
 
 @Aggregates({EventSource.G1GC,EventSource.GENERATIONAL,EventSource.ZGC,EventSource.SHENANDOAH})
 public class CollectionCycleCountsAggregator extends Aggregator<CollectionCycleCountsAggregation> {
@@ -19,21 +19,21 @@ public CollectionCycleCountsAggregator(CollectionCycleCountsAggregation results)
         register(GenerationalGCPauseEvent.class, this::count);
         register(G1GCPauseEvent.class, this::count);
         register(G1GCConcurrentEvent.class, this::count);
-        register(FullZGCCycle.class,this::count);
-        register(MajorZGCCycle.class,this::count);
-        register(MinorZGCCycle.class,this::count);
+        register(ZGCFullCollection.class, this::count);
+        register(ZGCOldCollection.class, this::count);
+        register(ZGCYoungCollection.class, this::count);
         register(ShenandoahCycle.class,this::count);
     }
 
-    private void count(FullZGCCycle event) {
+    private void count(ZGCFullCollection event) {
         aggregation().count(event.getGarbageCollectionType());
     }
 
-    private void count(MajorZGCCycle event) {
+    private void count(ZGCOldCollection event) {
         aggregation().count(event.getGarbageCollectionType());
     }
 
-    private void count(MinorZGCCycle event) {
+    private void count(ZGCYoungCollection event) {
         aggregation().count(event.getGarbageCollectionType());
     }
 

IT/src/main/java/com/microsoft/gctoolkit/integration/aggregation/HeapOccupancyAfterCollectionAggregator.java

@@ -6,9 +6,9 @@
 import com.microsoft.gctoolkit.event.g1gc.G1GCPauseEvent;
 import com.microsoft.gctoolkit.event.generational.GenerationalGCPauseEvent;
 import com.microsoft.gctoolkit.event.shenandoah.ShenandoahCycle;
-import com.microsoft.gctoolkit.event.zgc.FullZGCCycle;
-import com.microsoft.gctoolkit.event.zgc.MajorZGCCycle;
-import com.microsoft.gctoolkit.event.zgc.MinorZGCCycle;
+import com.microsoft.gctoolkit.event.zgc.ZGCFullCollection;
+import com.microsoft.gctoolkit.event.zgc.ZGCOldCollection;
+import com.microsoft.gctoolkit.event.zgc.ZGCYoungCollection;
 
 @Aggregates({EventSource.G1GC,EventSource.GENERATIONAL,EventSource.ZGC,EventSource.SHENANDOAH})
 public class HeapOccupancyAfterCollectionAggregator extends Aggregator<HeapOccupancyAfterCollectionAggregation> {
@@ -17,17 +17,17 @@ public HeapOccupancyAfterCollectionAggregator(HeapOccupancyAfterCollectionAggreg
         super(results);
         register(GenerationalGCPauseEvent.class, this::extractHeapOccupancy);
         register(G1GCPauseEvent.class, this::extractHeapOccupancy);
-        register(FullZGCCycle.class,this::extractHeapOccupancy);
-        register(MajorZGCCycle.class,this::extractHeapOccupancy);
-        register(MinorZGCCycle.class,this::extractHeapOccupancy);
+        register(ZGCFullCollection.class, this::extractHeapOccupancy);
+        register(ZGCOldCollection.class, this::extractHeapOccupancy);
+        register(ZGCYoungCollection.class, this::extractHeapOccupancy);
         register(ShenandoahCycle.class,this::extractHeapOccupancy);
     }
 
-    private void extractHeapOccupancy(MinorZGCCycle event) {
-        aggregation().addDataPoint(event.getGarbageCollectionType(), event.getDateTimeStamp(), event.getYoungCycle().getMemorySummary().getOccupancyAfter());
+    private void extractHeapOccupancy(ZGCYoungCollection event) {
+        aggregation().addDataPoint(event.getGarbageCollectionType(), event.getDateTimeStamp(), event.getMemorySummary().getOccupancyAfter());
     }
 
-    private void extractHeapOccupancy(MajorZGCCycle event) {
+    private void extractHeapOccupancy(ZGCOldCollection event) {
         aggregation().addDataPoint(event.getGarbageCollectionType(), event.getDateTimeStamp(), event.getMemorySummary().getOccupancyAfter());
     }
 
@@ -41,7 +41,7 @@ private void extractHeapOccupancy(G1GCPauseEvent event) {
             aggregation().addDataPoint(event.getGarbageCollectionType(), event.getDateTimeStamp(), event.getHeap().getOccupancyAfterCollection());
     }
 
-    private void extractHeapOccupancy(FullZGCCycle event) {
+    private void extractHeapOccupancy(ZGCFullCollection event) {
         aggregation().addDataPoint(event.getGarbageCollectionType(), event.getDateTimeStamp(), event.getMemorySummary().getOccupancyAfter());
     }
 

api/src/main/java/com/microsoft/gctoolkit/event/GarbageCollectionTypes.java

@@ -56,8 +56,9 @@ public enum GarbageCollectionTypes implements LabelledGCEventType {
     G1Trap("G1GC Trap"),
     Unknown("Unknown"),
     ZGCFull("ZGC FULL"),
-    ZGCMajor("ZGC Major"),
-    ZGCMinor("ZGC Minor"),
+    ZGCMajorOld("ZGC Major Old"),
+    ZGCMajorYoung("ZGC Major Young"),
+    ZGCMinorYoung("ZGC Minor Young"),
     Shenandoah("Shenandoah");
 
     private final String label;