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Allow routing commands with ?retry_failed=true (#42658)
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We respect allocation deciders, including the `MaxRetryAllocationDecider`, when
executing reroute commands. If you specify `?retry_failed=true` then the retry
counter is reset, but today this does not happen until after trying to execute
the reroute commands. This means that if an allocation has repeatedly failed,
but you want to take control and assign a shard to a particular node to work
around the repeated failures, you cannot execute the routing command in the
same call to `POST /_cluster/reroute` as the one that resets the failure
counter.

This commit fixes this by resetting the failure counter first, meaning that you
can now explicitly allocate a repeatedly-failed shard like this:

```
POST /_cluster/reroute?retry_failed=true
{
  "commands": [
    {
      "allocate_replica": {
        "index": "blahblah",
        "shard": 2,
        "node": "node-4"
      }
    }
  ]
}
```

Fixes #39546
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vigyasharma authored and DaveCTurner committed Jun 10, 2019
1 parent 036f9c4 commit 2521873
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Original file line number Diff line number Diff line change
Expand Up @@ -337,16 +337,16 @@ public CommandsResult reroute(final ClusterState clusterState, AllocationCommand
allocation.debugDecision(true);
// we ignore disable allocation, because commands are explicit
allocation.ignoreDisable(true);
RoutingExplanations explanations = commands.execute(allocation, explain);
// we revert the ignore disable flag, since when rerouting, we want the original setting to take place
allocation.ignoreDisable(false);
// the assumption is that commands will move / act on shards (or fail through exceptions)
// so, there will always be shard "movements", so no need to check on reroute

if (retryFailed) {
resetFailedAllocationCounter(allocation);
}

RoutingExplanations explanations = commands.execute(allocation, explain);
// we revert the ignore disable flag, since when rerouting, we want the original setting to take place
allocation.ignoreDisable(false);
// the assumption is that commands will move / act on shards (or fail through exceptions)
// so, there will always be shard "movements", so no need to check on reroute
reroute(allocation);
return new CommandsResult(explanations, buildResultAndLogHealthChange(clusterState, allocation, "reroute commands"));
}
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Original file line number Diff line number Diff line change
@@ -0,0 +1,97 @@
/*
* Licensed to Elasticsearch under one or more contributor
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* this work for additional information regarding copyright
* ownership. Elasticsearch 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
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*/

package org.elasticsearch.cluster.routing.allocation;

import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.Version;
import org.elasticsearch.cluster.ClusterName;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.ESAllocationTestCase;
import org.elasticsearch.cluster.metadata.IndexMetaData;
import org.elasticsearch.cluster.metadata.MetaData;
import org.elasticsearch.cluster.node.DiscoveryNodes;
import org.elasticsearch.cluster.routing.RoutingTable;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.ShardRoutingState;
import org.elasticsearch.cluster.routing.allocation.command.AllocateReplicaAllocationCommand;
import org.elasticsearch.cluster.routing.allocation.command.AllocationCommands;
import org.elasticsearch.cluster.routing.allocation.decider.MaxRetryAllocationDecider;
import org.elasticsearch.common.settings.Settings;

import java.util.Collections;
import java.util.List;

import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.sameInstance;

public class RetryFailedAllocationTests extends ESAllocationTestCase {

private MockAllocationService strategy;
private ClusterState clusterState;
private final String INDEX_NAME = "index";

@Override
public void setUp() throws Exception {
super.setUp();
MetaData metaData = MetaData.builder().put(IndexMetaData.builder(INDEX_NAME)
.settings(settings(Version.CURRENT)).numberOfShards(1).numberOfReplicas(1)).build();
RoutingTable routingTable = RoutingTable.builder().addAsNew(metaData.index(INDEX_NAME)).build();
clusterState = ClusterState.builder(ClusterName.DEFAULT).metaData(metaData).routingTable(routingTable)
.nodes(DiscoveryNodes.builder().add(newNode("node1")).add(newNode("node2"))).build();
strategy = createAllocationService(Settings.EMPTY);
}

private ShardRouting getPrimary() {
return clusterState.getRoutingTable().index(INDEX_NAME).shard(0).primaryShard();
}

private ShardRouting getReplica() {
return clusterState.getRoutingTable().index(INDEX_NAME).shard(0).replicaShards().get(0);
}

public void testRetryFailedResetForAllocationCommands() {
final int retries = MaxRetryAllocationDecider.SETTING_ALLOCATION_MAX_RETRY.get(Settings.EMPTY);
clusterState = strategy.reroute(clusterState, "initial allocation");
clusterState = strategy.applyStartedShards(clusterState, Collections.singletonList(getPrimary()));

// Exhaust all replica allocation attempts with shard failures
for (int i = 0; i < retries; i++) {
List<FailedShard> failedShards = Collections.singletonList(
new FailedShard(getReplica(), "failing-shard::attempt-" + i,
new ElasticsearchException("simulated"), randomBoolean()));
clusterState = strategy.applyFailedShards(clusterState, failedShards);
clusterState = strategy.reroute(clusterState, "allocation retry attempt-" + i);
}
assertThat("replica should not be assigned", getReplica().state(), equalTo(ShardRoutingState.UNASSIGNED));
assertThat("reroute should be a no-op", strategy.reroute(clusterState, "test"), sameInstance(clusterState));

// Now allocate replica with retry_failed flag set
AllocationService.CommandsResult result = strategy.reroute(clusterState,
new AllocationCommands(new AllocateReplicaAllocationCommand(INDEX_NAME, 0,
getPrimary().currentNodeId().equals("node1") ? "node2" : "node1")),
false, true);
clusterState = result.getClusterState();

assertEquals(ShardRoutingState.INITIALIZING, getReplica().state());
clusterState = strategy.applyStartedShards(clusterState, Collections.singletonList(getReplica()));
assertEquals(ShardRoutingState.STARTED, getReplica().state());
assertFalse(clusterState.getRoutingNodes().hasUnassignedShards());
}
}

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