rmdmattingly commented on code in PR #6651:
URL: https://github.com/apache/hbase/pull/6651#discussion_r1932832072
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hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalancerClusterState.java:
##########
@@ -711,6 +726,44 @@ enum LocalityType {
RACK
}
+ public List<RegionPlan> convertActionToPlans(BalanceAction action) {
Review Comment:
RegionPlans are much simpler than balance actions because they can represent
the consequences of every type of balance action. With that in mind, I chose to
have balancer conditionals only be concerned with RegionPlans so that their
implementations could be simpler — but it means that I need to convert
BalanceActions to region plans, without applying the plans, for evaluation
against conditionals. Thus, this method needed to be added
##########
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalancerClusterState.java:
##########
@@ -905,6 +975,52 @@ int[] addRegion(int[] regions, int regionIndex) {
return newRegions;
}
+ int[] removeRegions(int[] regions, Set<Integer> regionIndicesToRemove) {
Review Comment:
This method, and the below addRegions, are just a nicer way to add/remove
regions from the BCS arrays in bulk
##########
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalancerConditionals.java:
##########
@@ -0,0 +1,203 @@
+/*
+ * 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.hadoop.hbase.master.balancer;
+
+import java.lang.reflect.Constructor;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+import org.apache.hadoop.conf.Configurable;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.master.RegionPlan;
+import org.apache.hadoop.hbase.util.ReflectionUtils;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableSet;
+
+/**
+ * Balancer conditionals supplement cost functions in the {@link
StochasticLoadBalancer}. Cost
+ * functions are insufficient and difficult to work with when making discrete
decisions; this is
+ * because they operate on a continuous scale, and each cost function's
multiplier affects the
+ * relative importance of every other cost function. So it is difficult to
meaningfully and clearly
+ * value many aspects of your region distribution via cost functions alone.
Conditionals allow you
+ * to very clearly define discrete rules that your balancer would ideally
follow. To clarify, a
+ * conditional violation will not block a region assignment because we would
prefer to have uptime
+ * than have perfectly intentional balance. But conditionals allow you to, for
example, define that
+ * a region's primary and secondary should not live on the same rack. Another
example, conditionals
+ * make it easy to define that system tables will ideally be isolated on their
own RegionServer
+ * (without needing to manage distinct RegionServer groups). Use of
conditionals may cause an
+ * extremely unbalanced cluster to exceed its max balancer runtime. This is
necessary because
+ * conditional candidate generation is quite expensive, and cutting it off
early could prevent us
+ * from finding a solution.
+ */
[email protected]
+final class BalancerConditionals implements Configurable {
Review Comment:
This acts as a unified interface for interacting with whatever
conditional(s) one might have enabled
##########
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/RegionPlanConditional.java:
##########
@@ -0,0 +1,125 @@
+/*
+ * 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.hadoop.hbase.master.balancer;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.master.RegionPlan;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
[email protected]
[email protected]
+public abstract class RegionPlanConditional {
+ private static final Logger LOG =
LoggerFactory.getLogger(RegionPlanConditional.class);
+ private BalancerClusterState cluster;
+
+ RegionPlanConditional(Configuration conf, BalancerClusterState cluster) {
+ this.cluster = cluster;
+ }
+
+ public enum ValidationLevel {
+ SERVER, // Just check server
+ HOST, // Check host and server
+ RACK // Check rack, host, and server
+ }
Review Comment:
All 3 checks will be necessary for replica balancing, but for most
conditionals (I envision a system table isolation conditional, for example) my
guess is that only server validation will be necessary. So I figured that this
is a nice way to let implementations be as simple as possible
##########
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BalanceAction.java:
##########
@@ -28,6 +28,7 @@ enum Type {
ASSIGN_REGION,
MOVE_REGION,
SWAP_REGIONS,
+ MOVE_BATCH,
Review Comment:
Conditional candidate generators will look at the entire cluster state, and
produce a series of moves that should move us towards compliance. To support
this, I thought a "batch move" balance action made sense
##########
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/SlopFixingCandidateGenerator.java:
##########
@@ -0,0 +1,104 @@
+/*
+ * 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.hadoop.hbase.master.balancer;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import org.apache.hadoop.hbase.ServerName;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A simple candidate generator that attempts to move regions from the
most-loaded servers to the
+ * least-loaded servers.
+ */
[email protected]
+final class SlopFixingCandidateGenerator extends
RegionPlanConditionalCandidateGenerator {
Review Comment:
This is a very time-effective way to resolve the sloppy servers that may be
produced by randomly distributing replicas across the cluster. I probably
anticipate this being useful in future conditionals too
##########
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java:
##########
@@ -515,6 +557,7 @@ private long calculateMaxSteps(BalancerClusterState
cluster) {
* approach the optimal state given enough steps.
*/
@Override
+ @SuppressWarnings("checkstyle:MethodLength")
Review Comment:
Open to the idea that we should actually clean this up a bit instead of
suppressing this warning, but the diff here is already big so I didn't want to
add a bunch of refactoring that made it harder to read
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