Aggregate worker will hold the metrics while there is no new metrics in. (#3100)

oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/worker/MetricsAggregateWorker.java

@@ -19,7 +19,7 @@
 package org.apache.skywalking.oap.server.core.analysis.worker;
 
 import java.util.*;
-import org.apache.skywalking.apm.commons.datacarrier.*;
+import org.apache.skywalking.apm.commons.datacarrier.DataCarrier;
 import org.apache.skywalking.apm.commons.datacarrier.consumer.*;
 import org.apache.skywalking.oap.server.core.UnexpectedException;
 import org.apache.skywalking.oap.server.core.analysis.data.*;
@@ -40,15 +40,10 @@ public class MetricsAggregateWorker extends AbstractWorker<Metrics> {
     private AbstractWorker<Metrics> nextWorker;
     private final DataCarrier<Metrics> dataCarrier;
     private final MergeDataCache<Metrics> mergeDataCache;
-    private final String modelName;
     private CounterMetrics aggregationCounter;
-    private final long l2AggregationSendCycle;
-    private long lastSendTimestamp;
 
-    MetricsAggregateWorker(ModuleDefineHolder moduleDefineHolder, AbstractWorker<Metrics> nextWorker,
-        String modelName) {
+    MetricsAggregateWorker(ModuleDefineHolder moduleDefineHolder, AbstractWorker<Metrics> nextWorker, String modelName) {
         super(moduleDefineHolder);
-        this.modelName = modelName;
         this.nextWorker = nextWorker;
         this.mergeDataCache = new MergeDataCache<>();
         String name = "METRICS_L1_AGGREGATION";
@@ -65,9 +60,6 @@ public class MetricsAggregateWorker extends AbstractWorker<Metrics> {
         MetricsCreator metricsCreator = moduleDefineHolder.find(TelemetryModule.NAME).provider().getService(MetricsCreator.class);
         aggregationCounter = metricsCreator.createCounter("metrics_aggregation", "The number of rows in aggregation",
             new MetricsTag.Keys("metricName", "level", "dimensionality"), new MetricsTag.Values(modelName, "1", "min"));
-        lastSendTimestamp = System.currentTimeMillis();
-
-        l2AggregationSendCycle = EnvUtil.getLong("METRICS_L1_AGGREGATION_SEND_CYCLE", 1000);
     }
 
     @Override public final void in(Metrics metrics) {
@@ -80,20 +72,8 @@ public class MetricsAggregateWorker extends AbstractWorker<Metrics> {
         aggregate(metrics);
 
         if (metrics.getEndOfBatchContext().isEndOfBatch()) {
-            if (shouldSend()) {
-                sendToNext();
-            }
-        }
-    }
-
-    private boolean shouldSend() {
-        long now = System.currentTimeMillis();
-        // Continue L2 aggregation in certain cycle.
-        if (now - lastSendTimestamp > l2AggregationSendCycle) {
-            lastSendTimestamp = now;
-            return true;
+            sendToNext();
         }
-        return false;
     }
 
     private void sendToNext() {