Fly-Style commented on code in PR #18819:
URL: https://github.com/apache/druid/pull/18819#discussion_r2619419631
##########
indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/supervisor/SeekableStreamSupervisor.java:
##########
@@ -4381,6 +4371,36 @@ public ConcurrentHashMap<PartitionIdType,
SequenceOffsetType> getPartitionOffset
return partitionOffsets;
}
+ /**
+ * Calculates the average poll-idle-ratio metric across all active tasks.
+ * This metric indicates how much time the consumer spends idle waiting for
data.
+ *
+ * @return the average poll-idle-ratio across all tasks, or 1 (full idle) if
no tasks or metrics are available
+ */
+ public double getPollIdleRatioMetric()
+ {
+ Map<String, Map<String, Object>> taskMetrics = getStats();
+ if (taskMetrics.isEmpty()) {
+ return 1.;
+ }
+
+ double sum = 0;
+ int count = 0;
+ for (Map<String, Object> groupMetrics : taskMetrics.values()) {
+ for (Object taskMetric : groupMetrics.values()) {
+ if (taskMetric instanceof Map) {
+ Object pollIdleRatio = ((Map<?, ?>) taskMetric).get("pollIdleRatio");
Review Comment:
https://github.com/apache/druid/pull/18819/commits/3cda48a34137ff82621b5b8dbef48d902163dceb
##########
indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/SeekableStreamIndexTaskRunner.java:
##########
@@ -1662,6 +1664,9 @@ public Map<String, Object> doGetRowStats()
returnMap.put("movingAverages", averagesMap);
returnMap.put("totals", totalsMap);
+ if (this.recordSupplier != null) {
+ returnMap.put("pollIdleRatio",
this.recordSupplier.getPollIdleRatioMetric());
Review Comment:
https://github.com/apache/druid/pull/18819/commits/3cda48a34137ff82621b5b8dbef48d902163dceb
##########
indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/supervisor/autoscaler/CostBasedAutoScaler.java:
##########
@@ -0,0 +1,275 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.indexing.seekablestream.supervisor.autoscaler;
+
+import org.apache.druid.indexing.overlord.supervisor.SupervisorSpec;
+import org.apache.druid.indexing.overlord.supervisor.autoscaler.LagStats;
+import
org.apache.druid.indexing.overlord.supervisor.autoscaler.SupervisorTaskAutoScaler;
+import
org.apache.druid.indexing.seekablestream.supervisor.SeekableStreamSupervisor;
+import org.apache.druid.java.util.common.StringUtils;
+import org.apache.druid.java.util.common.concurrent.Execs;
+import org.apache.druid.java.util.emitter.EmittingLogger;
+import org.apache.druid.java.util.emitter.service.ServiceEmitter;
+import org.apache.druid.java.util.emitter.service.ServiceMetricEvent;
+import org.apache.druid.query.DruidMetrics;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * Cost-based auto-scaler for seekable stream supervisors.
+ * Uses a cost function combining lag and idle time metrics to determine
optimal task counts.
+ * Task counts are selected from predefined values (not arbitrary factors).
+ * Scale-up happens incrementally, scale-down only during task rollover.
+ */
+public class CostBasedAutoScaler implements SupervisorTaskAutoScaler
+{
+ private static final EmittingLogger log = new
EmittingLogger(CostBasedAutoScaler.class);
+
+ private static final int SCALE_FACTOR_DISCRETE_DISTANCE = 2;
+ public static final String OPTIMAL_TASK_COUNT_METRIC =
"task/autoScaler/costBased/optimalTaskCount";
+
+ private static final Map<Integer, int[]> FACTORS_CACHE = new
LinkedHashMap<>();
+ private static final int FACTORS_CACHE_MAX_SIZE = 10; // Enough for most
scenarios, almost capacity * loadFactor.
+
+ private final String supervisorId;
+ private final SeekableStreamSupervisor supervisor;
+ private final ServiceEmitter emitter;
+ private final SupervisorSpec spec;
+ private final CostBasedAutoScalerConfig config;
+ private final ServiceMetricEvent.Builder metricBuilder;
+ /**
+ * Atomic reference to CostMetrics object. All operations must be performed
+ * with sequentially consistent semantics (volatile reads/writes).
+ * However, it may be fine-tuned with acquire/release semantics,
+ * but requires careful reasoning about correctness.
+ */
+ private final AtomicReference<CostMetrics> currentMetrics;
+ private final ScheduledExecutorService autoscalerExecutor;
+ private final WeightedCostFunction costFunction;
+
+ public CostBasedAutoScaler(
+ SeekableStreamSupervisor supervisor,
+ CostBasedAutoScalerConfig config,
+ SupervisorSpec spec,
+ ServiceEmitter emitter
+ )
+ {
+ this.config = config;
+ this.spec = spec;
+ this.supervisor = supervisor;
+ this.supervisorId = spec.getId();
+ this.emitter = emitter;
+
+ this.currentMetrics = new AtomicReference<>(null);
+ this.costFunction = new WeightedCostFunction();
+
+ this.autoscalerExecutor =
Execs.scheduledSingleThreaded(StringUtils.encodeForFormat(spec.getId()));
+ this.metricBuilder = ServiceMetricEvent.builder()
+
.setDimension(DruidMetrics.DATASOURCE, supervisorId)
+ .setDimension(
+ DruidMetrics.STREAM,
+
this.supervisor.getIoConfig().getStream()
+ );
+ }
+
+ @Override
+ public void start()
+ {
+ Callable<Integer> scaleAction = () ->
computeOptimalTaskCount(currentMetrics);
+ Runnable onSuccessfulScale = () -> currentMetrics.set(null);
+
+ autoscalerExecutor.scheduleAtFixedRate(
+ this::collectMetrics,
+ config.getMetricsCollectionIntervalMillis(),
+ config.getMetricsCollectionIntervalMillis(),
+ TimeUnit.MILLISECONDS
+ );
+
+ autoscalerExecutor.scheduleAtFixedRate(
+ supervisor.buildDynamicAllocationTask(scaleAction, onSuccessfulScale,
emitter),
+ config.getScaleActionStartDelayMillis(),
+ config.getScaleActionPeriodMillis(),
+ TimeUnit.MILLISECONDS
+ );
+
+ log.info(
+ "CostBasedAutoScaler started for dataSource [%s]: collecting metrics
every [%d]ms, "
+ + "evaluating scaling every [%d]ms",
+ supervisorId,
+ config.getMetricsCollectionIntervalMillis(),
+ config.getScaleActionPeriodMillis()
+ );
+ }
+
+ @Override
+ public void stop()
+ {
+ autoscalerExecutor.shutdownNow();
+ log.info("CostBasedAutoScaler stopped for dataSource [%s]", supervisorId);
+ }
+
+ @Override
+ public void reset()
+ {
+ currentMetrics.set(null);
+ }
+
+ private void collectMetrics()
+ {
+ if (spec.isSuspended()) {
+ log.debug("Supervisor [%s] is suspended, skipping a metrics collection",
supervisorId);
+ return;
+ }
+
+ final LagStats lagStats = supervisor.computeLagStats();
+ if (lagStats == null) {
+ log.debug("Lag stats unavailable for dataSource [%s], skipping
collection", supervisorId);
+ return;
+ }
+
+ final int currentTaskCount = supervisor.getIoConfig().getTaskCount();
+ final int partitionCount = supervisor.getPartitionCount();
+ final double pollIdleRatio = supervisor.getPollIdleRatioMetric();
+
+ currentMetrics.set(
+ new CostMetrics(
+ lagStats.getAvgLag(),
+ currentTaskCount,
+ partitionCount,
+ pollIdleRatio
+ )
+ );
+
+ log.debug("Collected metrics for dataSource [%s]", supervisorId);
+ }
+
+ /**
+ * @return optimal task count, or -1 if no scaling action needed
+ */
+ public int computeOptimalTaskCount(AtomicReference<CostMetrics>
currentMetricsRef)
Review Comment:
https://github.com/apache/druid/pull/18819/commits/3cda48a34137ff82621b5b8dbef48d902163dceb
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