[FLINK-36409] Publish some autoscaler metrics during stabilisation period

examples/autoscaling/autoscaling-dynamic.yaml

@@ -27,7 +27,7 @@ spec:
     job.autoscaler.enabled: "true"
     job.autoscaler.stabilization.interval: "1m"
     job.autoscaler.metrics.window: "15m"
-    job.autoscaler.target.utilization: "0.5"
+    job.autoscaler.utilization.target: "0.5"
     job.autoscaler.target.utilization.boundary: "0.3"
     pipeline.max-parallelism: "32"
     taskmanager.numberOfTaskSlots: "4"

flink-autoscaler/src/main/java/org/apache/flink/autoscaler/ScalingMetricCollector.java

@@ -149,24 +149,39 @@ public CollectedMetricHistory updateMetrics(
         // Add scaling metrics to history if they were computed successfully
         metricHistory.put(now, scalingMetrics);
 
-        if (isStabilizing) {
-            LOG.info("Stabilizing until {}", readable(stableTime));
-            stateStore.storeCollectedMetrics(ctx, metricHistory);
-            return new CollectedMetricHistory(topology, Collections.emptySortedMap(), jobRunningTs);
-        }
-
         var collectedMetrics = new CollectedMetricHistory(topology, metricHistory, jobRunningTs);
         if (now.isBefore(windowFullTime)) {
-            LOG.info("Metric window not full until {}", readable(windowFullTime));
+            if (isStabilizing) {
+                LOG.info("Stabilizing until {}", readable(stableTime));
+            } else {
+                LOG.info(
+                        "Metric window is not full until {}. {} samples collected so far",
+                        readable(windowFullTime),
+                        metricHistory.size());
+            }
         } else {
             collectedMetrics.setFullyCollected(true);
             // Trim metrics outside the metric window from metrics history
-            metricHistory.headMap(now.minus(metricWindowSize)).clear();
+            var trimBefore = now.minus(metricWindowSize);
+            int numDropped = removeMetricsBefore(trimBefore, metricHistory);
+            LOG.debug(
+                    "Metric window is now full. Dropped {} samples before {}, keeping {}.",
+                    numDropped,
+                    readable(trimBefore),
+                    metricHistory.size());
         }
         stateStore.storeCollectedMetrics(ctx, metricHistory);
         return collectedMetrics;
     }
 
+    private int removeMetricsBefore(
+            Instant cutOffTimestamp, SortedMap<Instant, CollectedMetrics> metricHistory) {
+        var toBeDropped = metricHistory.headMap(cutOffTimestamp);
+        var numDropped = toBeDropped.size();
+        toBeDropped.clear();
+        return numDropped;
+    }
+
     protected abstract Map<FlinkMetric, Metric> queryJmMetrics(Context ctx) throws Exception;
 
     protected abstract Map<FlinkMetric, AggregatedMetric> queryTmMetrics(Context ctx)

flink-autoscaler/src/test/java/org/apache/flink/autoscaler/MetricsCollectionAndEvaluationTest.java

@@ -129,13 +129,13 @@ public void testEndToEnd() throws Exception {
 
         setDefaultMetrics(metricsCollector);
 
-        // We haven't left the stabilization period
-        // => no metrics reporting and collection should take place
+        // We haven't left the stabilization period, but we're collecting and returning the metrics
+        // for reporting
         var collectedMetrics = metricsCollector.updateMetrics(context, stateStore);
-        assertTrue(collectedMetrics.getMetricHistory().isEmpty());
+        assertEquals(1, collectedMetrics.getMetricHistory().size());
 
-        // We haven't collected a full window yet, no metrics should be reported but metrics should
-        // still get collected.
+        // We haven't collected a full window yet, but we're collecting and returning the metrics
+        // for reporting
         clock = Clock.offset(clock, conf.get(AutoScalerOptions.STABILIZATION_INTERVAL));
         metricsCollector.setClock(clock);
         collectedMetrics = metricsCollector.updateMetrics(context, stateStore);
@@ -294,12 +294,12 @@ public void testJobDetailsRestCompatibility() throws JsonProcessingException {
     public void testMetricCollectorWindow() throws Exception {
         setDefaultMetrics(metricsCollector);
         var metricsHistory = metricsCollector.updateMetrics(context, stateStore);
-        assertEquals(0, metricsHistory.getMetricHistory().size());
+        assertEquals(1, metricsHistory.getMetricHistory().size());
 
-        // Not stable, nothing should be collected
+        // Not stable, metrics collected and reported
         metricsCollector.setClock(Clock.offset(clock, Duration.ofSeconds(1)));
         metricsHistory = metricsCollector.updateMetrics(context, stateStore);
-        assertEquals(0, metricsHistory.getMetricHistory().size());
+        assertEquals(2, metricsHistory.getMetricHistory().size());
 
         // Update clock to stable time
         var conf = context.getConfiguration();
@@ -336,10 +336,10 @@ public void testMetricCollectorWindow() throws Exception {
         metricsHistory = metricsCollector.updateMetrics(context, stateStore);
         assertEquals(1, metricsHistory.getMetricHistory().size());
 
-        // Existing metrics should be cleared on job updates
+        // Existing metrics should be cleared on job updates, and start collecting from fresh
         metricsCollector.setJobUpdateTs(clock.instant().plus(Duration.ofDays(10)));
         metricsHistory = metricsCollector.updateMetrics(context, stateStore);
-        assertEquals(0, metricsHistory.getMetricHistory().size());
+        assertEquals(1, metricsHistory.getMetricHistory().size());
     }
 
     @Test
@@ -351,10 +351,11 @@ public void testClearHistoryOnTopoChange() throws Exception {
 
         setDefaultMetrics(metricsCollector);
 
-        // We haven't left the stabilization period
-        // => no metrics reporting and collection should take place
+        // We haven't left the stabilization period, we're returning the metrics
+        // but don't act on it since the metric window is not full yet
         var collectedMetrics = metricsCollector.updateMetrics(context, stateStore);
-        assertTrue(collectedMetrics.getMetricHistory().isEmpty());
+        assertFalse(collectedMetrics.getMetricHistory().isEmpty());
+        assertFalse(collectedMetrics.isFullyCollected());
     }
 
     @Test
@@ -571,19 +572,18 @@ public void testMetricCollectionDuringStabilization() throws Exception {
                 .set(AutoScalerOptions.STABILIZATION_INTERVAL, Duration.ofMillis(100));
         context.getConfiguration().set(AutoScalerOptions.METRICS_WINDOW, Duration.ofMillis(100));
 
-        // Within stabilization period we simply collect metrics but do not return them
+        // Until window is full (time=200) we keep returning stabilizing metrics
         metricsCollector.setClock(Clock.fixed(Instant.ofEpochMilli(50), ZoneId.systemDefault()));
-        assertTrue(
-                metricsCollector.updateMetrics(context, stateStore).getMetricHistory().isEmpty());
+        assertEquals(
+                1, metricsCollector.updateMetrics(context, stateStore).getMetricHistory().size());
         assertEquals(1, stateStore.getCollectedMetrics(context).size());
         metricsCollector.setClock(Clock.fixed(Instant.ofEpochMilli(60), ZoneId.systemDefault()));
-        assertTrue(
-                metricsCollector.updateMetrics(context, stateStore).getMetricHistory().isEmpty());
+        assertEquals(
+                2, metricsCollector.updateMetrics(context, stateStore).getMetricHistory().size());
         assertEquals(2, stateStore.getCollectedMetrics(context).size());
 
         testTolerateMetricsMissingDuringStabilizationPhase(topology);
 
-        // Until window is full (time=200) we keep returning stabilizing metrics
         metricsCollector.setClock(Clock.fixed(Instant.ofEpochMilli(150), ZoneId.systemDefault()));
         assertEquals(
                 3, metricsCollector.updateMetrics(context, stateStore).getMetricHistory().size());