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Ensuring that the ShrinkAction does not hang if total shards per node is too low #76732

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Aug 20, 2021
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5 changes: 5 additions & 0 deletions docs/reference/ilm/actions/ilm-shrink.asciidoc
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,11 @@ stream. You cannot perform the `shrink` action on a write index.
To use the `shrink` action in the `hot` phase, the `rollover` action *must* be
present. If no rollover action is configured, {ilm-init} will reject the policy.

The shrink action will unset the index's index.routing.allocation.total_shards_per_node
setting, meaning that there will be no limit. This is to ensure that all shards of the
index can be copied to a single node. This setting change will persist on the index
even after the step completes.

[IMPORTANT]
If the shrink action is used on a <<ccr-put-follow,follower index>>, policy
execution waits until the leader index rolls over (or is <<skipping-rollover,
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
import org.elasticsearch.cluster.routing.allocation.decider.FilterAllocationDecider;
import org.elasticsearch.cluster.routing.allocation.decider.NodeShutdownAllocationDecider;
import org.elasticsearch.cluster.routing.allocation.decider.NodeVersionAllocationDecider;
import org.elasticsearch.cluster.routing.allocation.decider.ShardsLimitAllocationDecider;
import org.elasticsearch.common.Randomness;
import org.elasticsearch.common.settings.ClusterSettings;
import org.elasticsearch.common.settings.Settings;
Expand Down Expand Up @@ -95,7 +96,8 @@ public void performAction(IndexMetadata indexMetadata, ClusterState clusterState

if (nodeId.isPresent()) {
Settings settings = Settings.builder()
.put(IndexMetadata.INDEX_ROUTING_REQUIRE_GROUP_SETTING.getKey() + "_id", nodeId.get()).build();
.put(IndexMetadata.INDEX_ROUTING_REQUIRE_GROUP_SETTING.getKey() + "_id", nodeId.get())
.putNull(ShardsLimitAllocationDecider.INDEX_TOTAL_SHARDS_PER_NODE_SETTING.getKey()).build();
UpdateSettingsRequest updateSettingsRequest = new UpdateSettingsRequest(indexName)
.masterNodeTimeout(TimeValue.MAX_VALUE)
.settings(settings);
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,7 @@ public static void assertSettingsRequestContainsValueFrom(UpdateSettingsRequest
assertArrayEquals(expectedIndices, request.indices());
assertThat(request.settings().get(settingsKey), anyOf(acceptableValues.stream().map(e -> equalTo(e)).collect(Collectors.toList())));
if (assertOnlyKeyInSettings) {
assertEquals(1, request.settings().size());
assertEquals(2, request.settings().size());
}
}

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
import org.elasticsearch.client.Request;
import org.elasticsearch.client.ResponseException;
import org.elasticsearch.cluster.metadata.IndexMetadata;
import org.elasticsearch.cluster.routing.allocation.decider.ShardsLimitAllocationDecider;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.settings.Settings;
Expand Down Expand Up @@ -302,4 +303,33 @@ public void testAutomaticRetryFailedShrinkAction() throws Exception {
});
expectThrows(ResponseException.class, () -> indexDocument(client(), index));
}

/*
* This test verifies that we can still shrink an index even if the total number of shards in the index is greater than
* index.routing.allocation.total_shards_per_node.
*/
public void testTotalShardsPerNodeTooLow() throws Exception {
int numShards = 4;
int divisor = randomFrom(2, 4);
int expectedFinalShards = numShards / divisor;
createIndexWithSettings(client(), index, alias, Settings.builder().put(SETTING_NUMBER_OF_SHARDS, numShards)
.put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
.put(ShardsLimitAllocationDecider.INDEX_TOTAL_SHARDS_PER_NODE_SETTING.getKey(), numShards - 2));
createNewSingletonPolicy(client(), policy, "warm", new ShrinkAction(expectedFinalShards, null));
updatePolicy(client(), index, policy);

String shrunkenIndexName = waitAndGetShrinkIndexName(client(), index);
assertBusy(() -> assertTrue(indexExists(shrunkenIndexName)), 60, TimeUnit.SECONDS);
assertBusy(() -> assertTrue(aliasExists(shrunkenIndexName, index)));
assertBusy(() -> assertThat(getStepKeyForIndex(client(), shrunkenIndexName),
equalTo(PhaseCompleteStep.finalStep("warm").getKey())));
assertBusy(() -> {
Map<String, Object> settings = getOnlyIndexSettings(client(), shrunkenIndexName);
assertThat(settings.get(SETTING_NUMBER_OF_SHARDS), equalTo(String.valueOf(expectedFinalShards)));
assertThat(settings.get(IndexMetadata.INDEX_BLOCKS_WRITE_SETTING.getKey()), equalTo("true"));
assertThat(settings.get(IndexMetadata.INDEX_ROUTING_REQUIRE_GROUP_SETTING.getKey() + "_id"), nullValue());
assertNull(settings.get(ShardsLimitAllocationDecider.INDEX_TOTAL_SHARDS_PER_NODE_SETTING.getKey()));
});
expectThrows(ResponseException.class, () -> indexDocument(client(), index));
}
}