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Posted to commits@druid.apache.org by as...@apache.org on 2021/07/30 14:10:15 UTC
[druid] branch master updated: Reduce method invocation of
reservoir sampling (#11257)
This is an automated email from the ASF dual-hosted git repository.
asdf2014 pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/druid.git
The following commit(s) were added to refs/heads/master by this push:
new b837421 Reduce method invocation of reservoir sampling (#11257)
b837421 is described below
commit b83742179a9035812875b4a77ce68be44ba5989f
Author: Yuanli Han <44...@users.noreply.github.com>
AuthorDate: Fri Jul 30 22:09:50 2021 +0800
Reduce method invocation of reservoir sampling (#11257)
* reduce method invocation of reservoir sampling
* add a dynamic parameter and add benchmark
* rebase
---
.../coordinator/BalancerStrategyBenchmark.java | 142 +++++++++++++++++++++
docs/configuration/index.md | 2 +
.../druid/server/coordinator/BalancerStrategy.java | 76 ++++++++++-
.../coordinator/CoordinatorDynamicConfig.java | 26 ++++
.../server/coordinator/CostBalancerStrategy.java | 16 ---
.../server/coordinator/RandomBalancerStrategy.java | 15 ---
.../coordinator/ReservoirSegmentSampler.java | 38 ++++++
.../server/coordinator/duty/BalanceSegments.java | 23 +++-
.../server/coordinator/BalanceSegmentsTest.java | 86 +++++++++----
.../coordinator/ReservoirSegmentSamplerTest.java | 8 +-
.../server/http/CoordinatorDynamicConfigTest.java | 2 +-
...coordinator-dynamic-config-dialog.spec.tsx.snap | 8 ++
.../druid-models/coordinator-dynamic-config.tsx | 13 ++
13 files changed, 382 insertions(+), 73 deletions(-)
diff --git a/benchmarks/src/test/java/org/apache/druid/server/coordinator/BalancerStrategyBenchmark.java b/benchmarks/src/test/java/org/apache/druid/server/coordinator/BalancerStrategyBenchmark.java
new file mode 100644
index 0000000..852403d
--- /dev/null
+++ b/benchmarks/src/test/java/org/apache/druid/server/coordinator/BalancerStrategyBenchmark.java
@@ -0,0 +1,142 @@
+/*
+ * 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.server.coordinator;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.util.concurrent.MoreExecutors;
+import io.vavr.collection.Stream;
+import org.apache.druid.client.ImmutableDruidDataSource;
+import org.apache.druid.client.ImmutableDruidServer;
+import org.apache.druid.java.util.common.Intervals;
+import org.apache.druid.server.coordination.DruidServerMetadata;
+import org.apache.druid.server.coordination.ServerType;
+import org.apache.druid.timeline.DataSegment;
+import org.joda.time.Interval;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+@Fork(value = 1)
+@Warmup(iterations = 10)
+@Measurement(iterations = 10)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+public class BalancerStrategyBenchmark
+{
+ private static final Random RANDOM = new Random(0);
+ private static final Interval TEST_SEGMENT_INTERVAL = Intervals.of("2012-03-15T00:00:00.000/2012-03-16T00:00:00.000");
+ private static final int NUMBER_OF_SERVERS = 20;
+
+ @Param({"default", "50percentOfSegmentsToConsiderPerMove", "useBatchedSegmentSampler"})
+ private String mode;
+
+ @Param({"10000", "100000", "1000000"})
+ private int numberOfSegments;
+
+ @Param({"10", "100", "1000"})
+ private int maxSegmentsToMove;
+
+ private final List<ServerHolder> serverHolders = new ArrayList<>();
+ private int reservoirSize = 1;
+ private double percentOfSegmentsToConsider = 100;
+ private final BalancerStrategy balancerStrategy = new CostBalancerStrategy(
+ MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(1))
+ );
+
+ @Setup(Level.Trial)
+ public void setup() throws IOException
+ {
+ switch (mode) {
+ case "50percentOfSegmentsToConsiderPerMove":
+ percentOfSegmentsToConsider = 50;
+ break;
+ case "useBatchedSegmentSampler":
+ reservoirSize = maxSegmentsToMove;
+ break;
+ default:
+ }
+
+ List<List<DataSegment>> segmentList = new ArrayList<>(NUMBER_OF_SERVERS);
+ Stream.range(0, NUMBER_OF_SERVERS).forEach(i -> segmentList.add(new ArrayList<>()));
+ for (int i = 0; i < numberOfSegments; i++) {
+ segmentList.get(RANDOM.nextInt(NUMBER_OF_SERVERS)).add(
+ new DataSegment(
+ "test",
+ TEST_SEGMENT_INTERVAL,
+ String.valueOf(i),
+ Collections.emptyMap(),
+ Collections.emptyList(),
+ Collections.emptyList(),
+ null,
+ 0,
+ 10L
+ )
+ );
+ }
+
+ for (List<DataSegment> segments : segmentList) {
+ serverHolders.add(
+ new ServerHolder(
+ new ImmutableDruidServer(
+ new DruidServerMetadata("id", "host", null, 10000000L, ServerType.HISTORICAL, "hot", 1),
+ 3000L,
+ ImmutableMap.of("test", new ImmutableDruidDataSource("test", Collections.emptyMap(), segments)),
+ segments.size()
+ ),
+ new LoadQueuePeonTester()
+ )
+ );
+ }
+ }
+
+ @Benchmark
+ public void pickSegmentsToMove(Blackhole blackhole)
+ {
+ Iterator<BalancerSegmentHolder> iterator = balancerStrategy.pickSegmentsToMove(
+ serverHolders,
+ Collections.emptySet(),
+ reservoirSize,
+ percentOfSegmentsToConsider
+ );
+ for (int i = 0; i < maxSegmentsToMove && iterator.hasNext(); i++) {
+ blackhole.consume(iterator.next());
+ }
+ }
+}
diff --git a/docs/configuration/index.md b/docs/configuration/index.md
index b1869ac..89ea6c2 100644
--- a/docs/configuration/index.md
+++ b/docs/configuration/index.md
@@ -809,6 +809,7 @@ A sample Coordinator dynamic config JSON object is shown below:
"mergeBytesLimit": 100000000,
"mergeSegmentsLimit" : 1000,
"maxSegmentsToMove": 5,
+ "useBatchedSegmentSampler": false,
"percentOfSegmentsToConsiderPerMove": 100,
"replicantLifetime": 15,
"replicationThrottleLimit": 10,
@@ -830,6 +831,7 @@ Issuing a GET request at the same URL will return the spec that is currently in
|`mergeBytesLimit`|The maximum total uncompressed size in bytes of segments to merge.|524288000L|
|`mergeSegmentsLimit`|The maximum number of segments that can be in a single [append task](../ingestion/tasks.md).|100|
|`maxSegmentsToMove`|The maximum number of segments that can be moved at any given time.|5|
+|`useBatchedSegmentSampler`|Boolean flag for whether or not we should use the Reservoir Sampling with a reservoir of size k instead of fixed size 1 to pick segments to move. This option can be enabled to speed up segment balancing process, especially if there are huge number of segments in the cluster or if there are too many segments to move.|false|
|`percentOfSegmentsToConsiderPerMove`|The percentage of the total number of segments in the cluster that are considered every time a segment needs to be selected for a move. Druid orders servers by available capacity ascending (the least available capacity first) and then iterates over the servers. For each server, Druid iterates over the segments on the server, considering them for moving. The default config of 100% means that every segment on every server is a candidate to be moved. Th [...]
|`replicantLifetime`|The maximum number of Coordinator runs for a segment to be replicated before we start alerting.|15|
|`replicationThrottleLimit`|The maximum number of segments that can be replicated at one time.|10|
diff --git a/server/src/main/java/org/apache/druid/server/coordinator/BalancerStrategy.java b/server/src/main/java/org/apache/druid/server/coordinator/BalancerStrategy.java
index 3d0ec0f..78ab951 100644
--- a/server/src/main/java/org/apache/druid/server/coordinator/BalancerStrategy.java
+++ b/server/src/main/java/org/apache/druid/server/coordinator/BalancerStrategy.java
@@ -55,7 +55,8 @@ public interface BalancerStrategy
ServerHolder findNewSegmentHomeReplicator(DataSegment proposalSegment, List<ServerHolder> serverHolders);
/**
- * Pick the best segment to move from one of the supplied set of servers according to the balancing strategy.
+ * Pick the best segments to move from one of the supplied set of servers according to the balancing strategy.
+ *
* @param serverHolders set of historicals to consider for moving segments
* @param broadcastDatasources Datasources that contain segments which were loaded via broadcast rules.
* Balancing strategies should avoid rebalancing segments for such datasources, since
@@ -63,20 +64,81 @@ public interface BalancerStrategy
* NOTE: this should really be handled on a per-segment basis, to properly support
* the interval or period-based broadcast rules. For simplicity of the initial
* implementation, only forever broadcast rules are supported.
+ * @param reservoirSize the reservoir size maintained by the Reservoir Sampling algorithm.
* @param percentOfSegmentsToConsider The percentage of the total number of segments that we will consider when
* choosing which segment to move. {@link CoordinatorDynamicConfig} defines a
* config percentOfSegmentsToConsiderPerMove that will be used as an argument
* for implementations of this method.
- *
- * @return {@link BalancerSegmentHolder} containing segment to move and server it currently resides on, or null if
- * there are no segments to pick from (i. e. all provided serverHolders are empty).
+ * @return Iterator for set of {@link BalancerSegmentHolder} containing segment to move and server they currently
+ * reside on, or empty if there are no segments to pick from (i. e. all provided serverHolders are empty).
*/
- @Nullable
- BalancerSegmentHolder pickSegmentToMove(
+ default Iterator<BalancerSegmentHolder> pickSegmentsToMove(
List<ServerHolder> serverHolders,
Set<String> broadcastDatasources,
+ int reservoirSize,
double percentOfSegmentsToConsider
- );
+ )
+ {
+ if (reservoirSize > 1) {
+ return new Iterator<BalancerSegmentHolder>()
+ {
+ private Iterator<BalancerSegmentHolder> it = sample();
+
+ private Iterator<BalancerSegmentHolder> sample()
+ {
+ return ReservoirSegmentSampler.getRandomBalancerSegmentHolders(
+ serverHolders,
+ broadcastDatasources,
+ reservoirSize
+ ).iterator();
+ }
+
+ @Override
+ public boolean hasNext()
+ {
+ if (it.hasNext()) {
+ return true;
+ }
+ it = sample();
+ return it.hasNext();
+ }
+
+ @Override
+ public BalancerSegmentHolder next()
+ {
+ return it.next();
+ }
+ };
+ }
+
+ return new Iterator<BalancerSegmentHolder>()
+ {
+ private BalancerSegmentHolder next = sample();
+
+ private BalancerSegmentHolder sample()
+ {
+ return ReservoirSegmentSampler.getRandomBalancerSegmentHolder(
+ serverHolders,
+ broadcastDatasources,
+ percentOfSegmentsToConsider
+ );
+ }
+
+ @Override
+ public boolean hasNext()
+ {
+ return next != null;
+ }
+
+ @Override
+ public BalancerSegmentHolder next()
+ {
+ BalancerSegmentHolder ret = next;
+ next = sample();
+ return ret;
+ }
+ };
+ }
/**
* Returns an iterator for a set of servers to drop from, ordered by preference of which server to drop from first
diff --git a/server/src/main/java/org/apache/druid/server/coordinator/CoordinatorDynamicConfig.java b/server/src/main/java/org/apache/druid/server/coordinator/CoordinatorDynamicConfig.java
index d125aa4..d4bf3e8 100644
--- a/server/src/main/java/org/apache/druid/server/coordinator/CoordinatorDynamicConfig.java
+++ b/server/src/main/java/org/apache/druid/server/coordinator/CoordinatorDynamicConfig.java
@@ -55,6 +55,7 @@ public class CoordinatorDynamicConfig
private final int mergeSegmentsLimit;
private final int maxSegmentsToMove;
private final double percentOfSegmentsToConsiderPerMove;
+ private final boolean useBatchedSegmentSampler;
private final int replicantLifetime;
private final int replicationThrottleLimit;
private final int balancerComputeThreads;
@@ -115,6 +116,7 @@ public class CoordinatorDynamicConfig
@JsonProperty("mergeSegmentsLimit") int mergeSegmentsLimit,
@JsonProperty("maxSegmentsToMove") int maxSegmentsToMove,
@JsonProperty("percentOfSegmentsToConsiderPerMove") @Nullable Double percentOfSegmentsToConsiderPerMove,
+ @JsonProperty("useBatchedSegmentSampler") boolean useBatchedSegmentSampler,
@JsonProperty("replicantLifetime") int replicantLifetime,
@JsonProperty("replicationThrottleLimit") int replicationThrottleLimit,
@JsonProperty("balancerComputeThreads") int balancerComputeThreads,
@@ -161,6 +163,7 @@ public class CoordinatorDynamicConfig
);
this.percentOfSegmentsToConsiderPerMove = percentOfSegmentsToConsiderPerMove;
+ this.useBatchedSegmentSampler = useBatchedSegmentSampler;
this.replicantLifetime = replicantLifetime;
this.replicationThrottleLimit = replicationThrottleLimit;
this.balancerComputeThreads = Math.max(balancerComputeThreads, 1);
@@ -273,6 +276,12 @@ public class CoordinatorDynamicConfig
}
@JsonProperty
+ public boolean useBatchedSegmentSampler()
+ {
+ return useBatchedSegmentSampler;
+ }
+
+ @JsonProperty
public int getReplicantLifetime()
{
return replicantLifetime;
@@ -377,6 +386,7 @@ public class CoordinatorDynamicConfig
", mergeSegmentsLimit=" + mergeSegmentsLimit +
", maxSegmentsToMove=" + maxSegmentsToMove +
", percentOfSegmentsToConsiderPerMove=" + percentOfSegmentsToConsiderPerMove +
+ ", useBatchedSegmentSampler=" + useBatchedSegmentSampler +
", replicantLifetime=" + replicantLifetime +
", replicationThrottleLimit=" + replicationThrottleLimit +
", balancerComputeThreads=" + balancerComputeThreads +
@@ -421,6 +431,9 @@ public class CoordinatorDynamicConfig
if (percentOfSegmentsToConsiderPerMove != that.percentOfSegmentsToConsiderPerMove) {
return false;
}
+ if (useBatchedSegmentSampler != that.useBatchedSegmentSampler) {
+ return false;
+ }
if (replicantLifetime != that.replicantLifetime) {
return false;
}
@@ -469,6 +482,7 @@ public class CoordinatorDynamicConfig
mergeSegmentsLimit,
maxSegmentsToMove,
percentOfSegmentsToConsiderPerMove,
+ useBatchedSegmentSampler,
replicantLifetime,
replicationThrottleLimit,
balancerComputeThreads,
@@ -501,6 +515,7 @@ public class CoordinatorDynamicConfig
private static final int DEFAULT_REPLICATION_THROTTLE_LIMIT = 10;
private static final int DEFAULT_BALANCER_COMPUTE_THREADS = 1;
private static final boolean DEFAULT_EMIT_BALANCING_STATS = false;
+ private static final boolean DEFAULT_USE_BATCHED_SEGMENT_SAMPLER = false;
private static final boolean DEFAULT_KILL_UNUSED_SEGMENTS_IN_ALL_DATA_SOURCES = false;
private static final int DEFAULT_MAX_SEGMENTS_IN_NODE_LOADING_QUEUE = 0;
private static final int DEFAULT_DECOMMISSIONING_MAX_SEGMENTS_TO_MOVE_PERCENT = 70;
@@ -513,6 +528,7 @@ public class CoordinatorDynamicConfig
private Integer mergeSegmentsLimit;
private Integer maxSegmentsToMove;
private Double percentOfSegmentsToConsiderPerMove;
+ private Boolean useBatchedSegmentSampler;
private Integer replicantLifetime;
private Integer replicationThrottleLimit;
private Boolean emitBalancingStats;
@@ -539,6 +555,7 @@ public class CoordinatorDynamicConfig
@JsonProperty("mergeSegmentsLimit") @Nullable Integer mergeSegmentsLimit,
@JsonProperty("maxSegmentsToMove") @Nullable Integer maxSegmentsToMove,
@JsonProperty("percentOfSegmentsToConsiderPerMove") @Nullable Double percentOfSegmentsToConsiderPerMove,
+ @JsonProperty("useBatchedSegmentSampler") Boolean useBatchedSegmentSampler,
@JsonProperty("replicantLifetime") @Nullable Integer replicantLifetime,
@JsonProperty("replicationThrottleLimit") @Nullable Integer replicationThrottleLimit,
@JsonProperty("balancerComputeThreads") @Nullable Integer balancerComputeThreads,
@@ -561,6 +578,7 @@ public class CoordinatorDynamicConfig
this.mergeSegmentsLimit = mergeSegmentsLimit;
this.maxSegmentsToMove = maxSegmentsToMove;
this.percentOfSegmentsToConsiderPerMove = percentOfSegmentsToConsiderPerMove;
+ this.useBatchedSegmentSampler = useBatchedSegmentSampler;
this.replicantLifetime = replicantLifetime;
this.replicationThrottleLimit = replicationThrottleLimit;
this.balancerComputeThreads = balancerComputeThreads;
@@ -606,6 +624,12 @@ public class CoordinatorDynamicConfig
return this;
}
+ public Builder withUseBatchedSegmentSampler(boolean useBatchedSegmentSampler)
+ {
+ this.useBatchedSegmentSampler = useBatchedSegmentSampler;
+ return this;
+ }
+
public Builder withReplicantLifetime(int replicantLifetime)
{
this.replicantLifetime = replicantLifetime;
@@ -689,6 +713,7 @@ public class CoordinatorDynamicConfig
maxSegmentsToMove == null ? DEFAULT_MAX_SEGMENTS_TO_MOVE : maxSegmentsToMove,
percentOfSegmentsToConsiderPerMove == null ? DEFAULT_PERCENT_OF_SEGMENTS_TO_CONSIDER_PER_MOVE
: percentOfSegmentsToConsiderPerMove,
+ useBatchedSegmentSampler == null ? DEFAULT_USE_BATCHED_SEGMENT_SAMPLER : useBatchedSegmentSampler,
replicantLifetime == null ? DEFAULT_REPLICANT_LIFETIME : replicantLifetime,
replicationThrottleLimit == null ? DEFAULT_REPLICATION_THROTTLE_LIMIT : replicationThrottleLimit,
balancerComputeThreads == null ? DEFAULT_BALANCER_COMPUTE_THREADS : balancerComputeThreads,
@@ -721,6 +746,7 @@ public class CoordinatorDynamicConfig
mergeSegmentsLimit == null ? defaults.getMergeSegmentsLimit() : mergeSegmentsLimit,
maxSegmentsToMove == null ? defaults.getMaxSegmentsToMove() : maxSegmentsToMove,
percentOfSegmentsToConsiderPerMove == null ? defaults.getPercentOfSegmentsToConsiderPerMove() : percentOfSegmentsToConsiderPerMove,
+ useBatchedSegmentSampler == null ? defaults.useBatchedSegmentSampler() : useBatchedSegmentSampler,
replicantLifetime == null ? defaults.getReplicantLifetime() : replicantLifetime,
replicationThrottleLimit == null ? defaults.getReplicationThrottleLimit() : replicationThrottleLimit,
balancerComputeThreads == null ? defaults.getBalancerComputeThreads() : balancerComputeThreads,
diff --git a/server/src/main/java/org/apache/druid/server/coordinator/CostBalancerStrategy.java b/server/src/main/java/org/apache/druid/server/coordinator/CostBalancerStrategy.java
index ac56544..8ff4f6a 100644
--- a/server/src/main/java/org/apache/druid/server/coordinator/CostBalancerStrategy.java
+++ b/server/src/main/java/org/apache/druid/server/coordinator/CostBalancerStrategy.java
@@ -35,7 +35,6 @@ import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.NavigableSet;
-import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;
import java.util.stream.Collectors;
@@ -210,21 +209,6 @@ public class CostBalancerStrategy implements BalancerStrategy
return totalCost;
}
-
- @Override
- public BalancerSegmentHolder pickSegmentToMove(
- final List<ServerHolder> serverHolders,
- Set<String> broadcastDatasources,
- double percentOfSegmentsToConsider
- )
- {
- return ReservoirSegmentSampler.getRandomBalancerSegmentHolder(
- serverHolders,
- broadcastDatasources,
- percentOfSegmentsToConsider
- );
- }
-
@Override
public Iterator<ServerHolder> pickServersToDrop(DataSegment toDrop, NavigableSet<ServerHolder> serverHolders)
{
diff --git a/server/src/main/java/org/apache/druid/server/coordinator/RandomBalancerStrategy.java b/server/src/main/java/org/apache/druid/server/coordinator/RandomBalancerStrategy.java
index 8f3b96d..d70d850 100644
--- a/server/src/main/java/org/apache/druid/server/coordinator/RandomBalancerStrategy.java
+++ b/server/src/main/java/org/apache/druid/server/coordinator/RandomBalancerStrategy.java
@@ -26,7 +26,6 @@ import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NavigableSet;
-import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;
import java.util.stream.Collectors;
@@ -54,20 +53,6 @@ public class RandomBalancerStrategy implements BalancerStrategy
}
@Override
- public BalancerSegmentHolder pickSegmentToMove(
- List<ServerHolder> serverHolders,
- Set<String> broadcastDatasources,
- double percentOfSegmentsToConsider
- )
- {
- return ReservoirSegmentSampler.getRandomBalancerSegmentHolder(
- serverHolders,
- broadcastDatasources,
- percentOfSegmentsToConsider
- );
- }
-
- @Override
public Iterator<ServerHolder> pickServersToDrop(DataSegment toDropSegment, NavigableSet<ServerHolder> serverHolders)
{
List<ServerHolder> serverList = new ArrayList<>(serverHolders);
diff --git a/server/src/main/java/org/apache/druid/server/coordinator/ReservoirSegmentSampler.java b/server/src/main/java/org/apache/druid/server/coordinator/ReservoirSegmentSampler.java
index dd43760..751f259 100644
--- a/server/src/main/java/org/apache/druid/server/coordinator/ReservoirSegmentSampler.java
+++ b/server/src/main/java/org/apache/druid/server/coordinator/ReservoirSegmentSampler.java
@@ -22,6 +22,7 @@ package org.apache.druid.server.coordinator;
import org.apache.druid.java.util.emitter.EmittingLogger;
import org.apache.druid.timeline.DataSegment;
+import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;
@@ -31,6 +32,42 @@ final class ReservoirSegmentSampler
private static final EmittingLogger log = new EmittingLogger(ReservoirSegmentSampler.class);
+ static List<BalancerSegmentHolder> getRandomBalancerSegmentHolders(
+ final List<ServerHolder> serverHolders,
+ Set<String> broadcastDatasources,
+ int k
+ )
+ {
+ List<BalancerSegmentHolder> holders = new ArrayList<>(k);
+ int numSoFar = 0;
+
+ for (ServerHolder server : serverHolders) {
+ if (!server.getServer().getType().isSegmentReplicationTarget()) {
+ // if the server only handles broadcast segments (which don't need to be rebalanced), we have nothing to do
+ continue;
+ }
+
+ for (DataSegment segment : server.getServer().iterateAllSegments()) {
+ if (broadcastDatasources.contains(segment.getDataSource())) {
+ // we don't need to rebalance segments that were assigned via broadcast rules
+ continue;
+ }
+
+ if (numSoFar < k) {
+ holders.add(new BalancerSegmentHolder(server.getServer(), segment));
+ numSoFar++;
+ continue;
+ }
+ int randNum = ThreadLocalRandom.current().nextInt(numSoFar + 1);
+ if (randNum < k) {
+ holders.set(randNum, new BalancerSegmentHolder(server.getServer(), segment));
+ }
+ numSoFar++;
+ }
+ }
+ return holders;
+ }
+
/**
* Iterates over segments that live on the candidate servers passed in {@link ServerHolder} and (possibly) picks a
* segment to return to caller in a {@link BalancerSegmentHolder} object.
@@ -42,6 +79,7 @@ final class ReservoirSegmentSampler
* returning immediately.
* @return
*/
+ @Deprecated
static BalancerSegmentHolder getRandomBalancerSegmentHolder(
final List<ServerHolder> serverHolders,
Set<String> broadcastDatasources,
diff --git a/server/src/main/java/org/apache/druid/server/coordinator/duty/BalanceSegments.java b/server/src/main/java/org/apache/druid/server/coordinator/duty/BalanceSegments.java
index d1fca19..218cf69 100644
--- a/server/src/main/java/org/apache/druid/server/coordinator/duty/BalanceSegments.java
+++ b/server/src/main/java/org/apache/druid/server/coordinator/duty/BalanceSegments.java
@@ -36,6 +36,7 @@ import org.apache.druid.timeline.DataSegment;
import org.apache.druid.timeline.SegmentId;
import java.util.HashMap;
+import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
@@ -55,6 +56,8 @@ public class BalanceSegments implements CoordinatorDuty
protected final Map<String, ConcurrentHashMap<SegmentId, BalancerSegmentHolder>> currentlyMovingSegments =
new HashMap<>();
+ private static final int DEFAULT_RESERVOIR_SIZE = 1;
+
public BalanceSegments(DruidCoordinator coordinator)
{
this.coordinator = coordinator;
@@ -180,22 +183,30 @@ public class BalanceSegments implements CoordinatorDuty
int maxSegmentsToMove
)
{
+ if (maxSegmentsToMove <= 0) {
+ return new Pair<>(0, 0);
+ }
+
final BalancerStrategy strategy = params.getBalancerStrategy();
final int maxIterations = 2 * maxSegmentsToMove;
final int maxToLoad = params.getCoordinatorDynamicConfig().getMaxSegmentsInNodeLoadingQueue();
int moved = 0, unmoved = 0;
+ Iterator<BalancerSegmentHolder> segmentsToMove = strategy.pickSegmentsToMove(
+ toMoveFrom,
+ params.getBroadcastDatasources(),
+ params.getCoordinatorDynamicConfig().useBatchedSegmentSampler() ? maxSegmentsToMove : DEFAULT_RESERVOIR_SIZE,
+ params.getCoordinatorDynamicConfig().getPercentOfSegmentsToConsiderPerMove()
+ );
+
//noinspection ForLoopThatDoesntUseLoopVariable
for (int iter = 0; (moved + unmoved) < maxSegmentsToMove; ++iter) {
- final BalancerSegmentHolder segmentToMoveHolder = strategy.pickSegmentToMove(
- toMoveFrom,
- params.getBroadcastDatasources(),
- params.getCoordinatorDynamicConfig().getPercentOfSegmentsToConsiderPerMove()
- );
- if (segmentToMoveHolder == null) {
+ if (!segmentsToMove.hasNext()) {
log.info("All servers to move segments from are empty, ending run.");
break;
}
+ final BalancerSegmentHolder segmentToMoveHolder = segmentsToMove.next();
+
// DruidCoordinatorRuntimeParams.getUsedSegments originate from SegmentsMetadataManager, i. e. that's a set of segments
// that *should* be loaded. segmentToMoveHolder.getSegment originates from ServerInventoryView, i. e. that may be
// any segment that happens to be loaded on some server, even if it is not used. (Coordinator closes such
diff --git a/server/src/test/java/org/apache/druid/server/coordinator/BalanceSegmentsTest.java b/server/src/test/java/org/apache/druid/server/coordinator/BalanceSegmentsTest.java
index 26175f6..76b1104 100644
--- a/server/src/test/java/org/apache/druid/server/coordinator/BalanceSegmentsTest.java
+++ b/server/src/test/java/org/apache/druid/server/coordinator/BalanceSegmentsTest.java
@@ -42,6 +42,7 @@ import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
+import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.Executors;
@@ -233,20 +234,26 @@ public class BalanceSegmentsTest
BalancerStrategy strategy = EasyMock.createMock(BalancerStrategy.class);
EasyMock.expect(
- strategy.pickSegmentToMove(
+ strategy.pickSegmentsToMove(
ImmutableList.of(
new ServerHolder(druidServer2, peon2, false)
),
broadcastDatasources,
+ 1,
100
)
).andReturn(
- new BalancerSegmentHolder(druidServer2, segment3)).andReturn(new BalancerSegmentHolder(druidServer2, segment4)
+ ImmutableList.of(
+ new BalancerSegmentHolder(druidServer2, segment3),
+ new BalancerSegmentHolder(druidServer2, segment4)
+ ).iterator()
);
- EasyMock.expect(strategy.pickSegmentToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt()))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment1))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment2));
+ EasyMock.expect(strategy.pickSegmentsToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt(), EasyMock.anyInt()))
+ .andReturn(
+ ImmutableList.of(
+ new BalancerSegmentHolder(druidServer1, segment1),
+ new BalancerSegmentHolder(druidServer1, segment2)).iterator());
EasyMock.expect(strategy.findNewSegmentHomeBalancer(EasyMock.anyObject(), EasyMock.anyObject()))
.andReturn(new ServerHolder(druidServer3, peon3))
@@ -309,11 +316,14 @@ public class BalanceSegmentsTest
mockCoordinator(coordinator);
BalancerStrategy strategy = EasyMock.createMock(BalancerStrategy.class);
- EasyMock.expect(strategy.pickSegmentToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt()))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment1))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment2))
- .andReturn(new BalancerSegmentHolder(druidServer2, segment3))
- .andReturn(new BalancerSegmentHolder(druidServer2, segment4));
+ EasyMock.expect(strategy.pickSegmentsToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt(), EasyMock.anyInt()))
+ .andReturn(ImmutableList.of(new BalancerSegmentHolder(druidServer1, segment1)).iterator());
+ EasyMock.expect(strategy.pickSegmentsToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt(), EasyMock.anyInt()))
+ .andReturn(
+ ImmutableList.of(
+ new BalancerSegmentHolder(druidServer1, segment2),
+ new BalancerSegmentHolder(druidServer2, segment3),
+ new BalancerSegmentHolder(druidServer2, segment4)).iterator());
EasyMock.expect(strategy.findNewSegmentHomeBalancer(EasyMock.anyObject(), EasyMock.anyObject()))
.andReturn(new ServerHolder(druidServer3, peon3))
@@ -358,8 +368,8 @@ public class BalanceSegmentsTest
mockCoordinator(coordinator);
BalancerStrategy strategy = EasyMock.createMock(BalancerStrategy.class);
- EasyMock.expect(strategy.pickSegmentToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt()))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment1))
+ EasyMock.expect(strategy.pickSegmentsToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt(), EasyMock.anyInt()))
+ .andReturn(ImmutableList.of(new BalancerSegmentHolder(druidServer1, segment1)).iterator())
.anyTimes();
EasyMock.expect(strategy.findNewSegmentHomeBalancer(EasyMock.anyObject(), EasyMock.anyObject())).andAnswer(() -> {
List<ServerHolder> holders = (List<ServerHolder>) EasyMock.getCurrentArguments()[1];
@@ -393,8 +403,8 @@ public class BalanceSegmentsTest
ServerHolder holder2 = new ServerHolder(druidServer2, peon2, false);
BalancerStrategy strategy = EasyMock.createMock(BalancerStrategy.class);
- EasyMock.expect(strategy.pickSegmentToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt()))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment1))
+ EasyMock.expect(strategy.pickSegmentsToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt(), EasyMock.anyInt()))
+ .andReturn(ImmutableList.of(new BalancerSegmentHolder(druidServer1, segment1)).iterator())
.once();
EasyMock.expect(strategy.findNewSegmentHomeBalancer(EasyMock.anyObject(), EasyMock.anyObject()))
.andReturn(holder2)
@@ -556,27 +566,29 @@ public class BalanceSegmentsTest
// The first call for decommissioning servers
EasyMock.expect(
- strategy.pickSegmentToMove(
+ strategy.pickSegmentsToMove(
ImmutableList.of(),
broadcastDatasources,
+ 1,
40
)
)
- .andReturn(null);
+ .andReturn(Collections.emptyIterator());
// The second call for the single non decommissioning server move
EasyMock.expect(
- strategy.pickSegmentToMove(
+ strategy.pickSegmentsToMove(
ImmutableList.of(
new ServerHolder(druidServer3, peon3, false),
new ServerHolder(druidServer2, peon2, false),
new ServerHolder(druidServer1, peon1, false)
),
broadcastDatasources,
+ 1,
40
)
)
- .andReturn(new BalancerSegmentHolder(druidServer2, segment3));
+ .andReturn(ImmutableList.of(new BalancerSegmentHolder(druidServer2, segment3)).iterator());
EasyMock.expect(strategy.findNewSegmentHomeBalancer(EasyMock.anyObject(), EasyMock.anyObject()))
.andReturn(new ServerHolder(druidServer3, peon3))
@@ -606,6 +618,30 @@ public class BalanceSegmentsTest
);
}
+ @Test
+ public void testUseBatchedSegmentSampler()
+ {
+ mockDruidServer(druidServer1, "1", "normal", 30L, 100L, segments);
+ mockDruidServer(druidServer2, "2", "normal", 0L, 100L, Collections.emptyList());
+ mockDruidServer(druidServer3, "3", "normal", 0L, 100L, Collections.emptyList());
+ mockDruidServer(druidServer4, "4", "normal", 0L, 100L, Collections.emptyList());
+
+ mockCoordinator(coordinator);
+
+ DruidCoordinatorRuntimeParams params = defaultRuntimeParamsBuilder(druidServers, peons)
+ .withDynamicConfigs(
+ CoordinatorDynamicConfig.builder()
+ .withMaxSegmentsToMove(2)
+ .withUseBatchedSegmentSampler(true)
+ .build()
+ )
+ .withBroadcastDatasources(broadcastDatasources)
+ .build();
+
+ params = new BalanceSegmentsTester(coordinator).run(params);
+ Assert.assertEquals(2L, params.getCoordinatorStats().getTieredStat("movedCount", "normal"));
+ }
+
private DruidCoordinatorRuntimeParams.Builder defaultRuntimeParamsBuilder(
List<ImmutableDruidServer> druidServers,
List<LoadQueuePeon> peons
@@ -716,13 +752,14 @@ public class BalanceSegmentsTest
}
@Override
- public BalancerSegmentHolder pickSegmentToMove(
+ public Iterator<BalancerSegmentHolder> pickSegmentsToMove(
List<ServerHolder> serverHolders,
Set<String> broadcastDatasources,
+ int numberOfSegments,
double percentOfSegmentsToConsider
)
{
- return pickOrder.get(pickCounter.getAndIncrement() % pickOrder.size());
+ return pickOrder.iterator();
}
@Override
@@ -745,18 +782,19 @@ public class BalanceSegmentsTest
// either decommissioning servers list or acitve ones (ie servers list is [2] or [1, 3])
BalancerStrategy strategy = EasyMock.createMock(BalancerStrategy.class);
EasyMock.expect(
- strategy.pickSegmentToMove(
+ strategy.pickSegmentsToMove(
ImmutableList.of(
new ServerHolder(druidServer2, peon2, true)
),
broadcastDatasources,
+ 1,
100
)
).andReturn(
- new BalancerSegmentHolder(druidServer2, segment2)
+ ImmutableList.of(new BalancerSegmentHolder(druidServer2, segment2)).iterator()
);
- EasyMock.expect(strategy.pickSegmentToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt()))
- .andReturn(new BalancerSegmentHolder(druidServer1, segment1));
+ EasyMock.expect(strategy.pickSegmentsToMove(EasyMock.anyObject(), EasyMock.anyObject(), EasyMock.anyInt(), EasyMock.anyDouble()))
+ .andReturn(ImmutableList.of(new BalancerSegmentHolder(druidServer1, segment1)).iterator());
EasyMock.expect(strategy.findNewSegmentHomeBalancer(EasyMock.anyObject(), EasyMock.anyObject()))
.andReturn(new ServerHolder(druidServer3, peon3))
.anyTimes();
diff --git a/server/src/test/java/org/apache/druid/server/coordinator/ReservoirSegmentSamplerTest.java b/server/src/test/java/org/apache/druid/server/coordinator/ReservoirSegmentSamplerTest.java
index f59f242..70086ab 100644
--- a/server/src/test/java/org/apache/druid/server/coordinator/ReservoirSegmentSamplerTest.java
+++ b/server/src/test/java/org/apache/druid/server/coordinator/ReservoirSegmentSamplerTest.java
@@ -174,10 +174,10 @@ public class ReservoirSegmentSamplerTest
Map<DataSegment, Integer> segmentCountMap = new HashMap<>();
for (int i = 0; i < iterations; i++) {
// due to the pseudo-randomness of this method, we may not select a segment every single time no matter what.
- BalancerSegmentHolder balancerSegmentHolder = ReservoirSegmentSampler.getRandomBalancerSegmentHolder(holderList, Collections.emptySet(), 100);
- if (balancerSegmentHolder != null) {
- segmentCountMap.put(balancerSegmentHolder.getSegment(), 1);
- }
+ segmentCountMap.put(
+ ReservoirSegmentSampler.getRandomBalancerSegmentHolders(holderList, Collections.emptySet(), 1).get(0).getSegment(),
+ 1
+ );
}
for (DataSegment segment : segments) {
diff --git a/server/src/test/java/org/apache/druid/server/http/CoordinatorDynamicConfigTest.java b/server/src/test/java/org/apache/druid/server/http/CoordinatorDynamicConfigTest.java
index e022082..b6776a8 100644
--- a/server/src/test/java/org/apache/druid/server/http/CoordinatorDynamicConfigTest.java
+++ b/server/src/test/java/org/apache/druid/server/http/CoordinatorDynamicConfigTest.java
@@ -389,7 +389,7 @@ public class CoordinatorDynamicConfigTest
Assert.assertEquals(
current,
new CoordinatorDynamicConfig
- .Builder(null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null)
+ .Builder(null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null)
.build(current)
);
}
diff --git a/web-console/src/dialogs/coordinator-dynamic-config-dialog/__snapshots__/coordinator-dynamic-config-dialog.spec.tsx.snap b/web-console/src/dialogs/coordinator-dynamic-config-dialog/__snapshots__/coordinator-dynamic-config-dialog.spec.tsx.snap
index 16f0386..b799bb5 100644
--- a/web-console/src/dialogs/coordinator-dynamic-config-dialog/__snapshots__/coordinator-dynamic-config-dialog.spec.tsx.snap
+++ b/web-console/src/dialogs/coordinator-dynamic-config-dialog/__snapshots__/coordinator-dynamic-config-dialog.spec.tsx.snap
@@ -169,6 +169,14 @@ exports[`coordinator dynamic config matches snapshot 1`] = `
"type": "number",
},
Object {
+ "defaultValue": false,
+ "info": <React.Fragment>
+ Boolean flag for whether or not we should use the Reservoir Sampling with a reservoir of size k instead of fixed size 1 to pick segments to move. This option can be enabled to speed up segment balancing process, especially if there are huge number of segments in the cluster or if there are too many segments to move.
+ </React.Fragment>,
+ "name": "useBatchedSegmentSampler",
+ "type": "boolean",
+ },
+ Object {
"defaultValue": 100,
"info": <React.Fragment>
The percentage of the total number of segments in the cluster that are considered every time a segment needs to be selected for a move. Druid orders servers by available capacity ascending (the least available capacity first) and then iterates over the servers. For each server, Druid iterates over the segments on the server, considering them for moving. The default config of 100% means that every segment on every server is a candidate to be moved. This should make sense for m [...]
diff --git a/web-console/src/druid-models/coordinator-dynamic-config.tsx b/web-console/src/druid-models/coordinator-dynamic-config.tsx
index 4ee4296..ee519ca 100644
--- a/web-console/src/druid-models/coordinator-dynamic-config.tsx
+++ b/web-console/src/druid-models/coordinator-dynamic-config.tsx
@@ -195,6 +195,19 @@ export const COORDINATOR_DYNAMIC_CONFIG_FIELDS: Field<CoordinatorDynamicConfig>[
),
},
{
+ name: 'useBatchedSegmentSampler',
+ type: 'boolean',
+ defaultValue: false,
+ info: (
+ <>
+ Boolean flag for whether or not we should use the Reservoir Sampling with a reservoir of
+ size k instead of fixed size 1 to pick segments to move. This option can be enabled to speed
+ up segment balancing process, especially if there are huge number of segments in the cluster
+ or if there are too many segments to move.
+ </>
+ ),
+ },
+ {
name: 'percentOfSegmentsToConsiderPerMove',
type: 'number',
defaultValue: 100,
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