Remove ALL shard check in CheckShrinkReadyStep (#35346)

Since it's still possible to shrink an index when replicas are unassigned, we
should not check that all copies are available when performing the shrink, since
we set the allocation requirement for a single node.

Resolves #35321

Author: dakrone

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/indexlifecycle/CheckShrinkReadyStep.java

@@ -8,7 +8,6 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.elasticsearch.action.support.ActiveShardCount;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.cluster.routing.IndexRoutingTable;
@@ -53,12 +52,6 @@ public Result isConditionMet(Index index, ClusterState clusterState) {
         // How many shards the node should have
         int expectedShardCount = idxMeta.getNumberOfShards();
 
-        if (ActiveShardCount.ALL.enoughShardsActive(clusterState, index.getName()) == false) {
-            logger.debug("[{}] shrink action for [{}] cannot make progress because not all shards are active",
-                getKey().getAction(), index.getName());
-            return new Result(false, new CheckShrinkReadyStep.Info("", expectedShardCount, -1));
-        }
-
         // The id of the node the shards should be on
         final String idShardsShouldBeOn = idxMeta.getSettings().get(IndexMetaData.INDEX_ROUTING_REQUIRE_GROUP_PREFIX + "._id");
         if (idShardsShouldBeOn == null) {

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/indexlifecycle/CheckShrinkReadyStepTests.java

@@ -221,7 +221,7 @@ public void testExecuteAllocateNotCompleteOnlyOneCopyAllocated() throws Exceptio
             new ClusterStateWaitStep.Result(false, new CheckShrinkReadyStep.Info("node1", 2, 1)));
     }
 
-    public void testExecuteAllocateUnassigned() throws Exception {
+    public void testExecuteAllocateReplicaUnassigned() {
         Index index = new Index(randomAlphaOfLengthBetween(1, 20), randomAlphaOfLengthBetween(1, 20));
         Map<String, String> requires = AllocateActionTests.randomMap(1, 5);
         Settings.Builder existingSettings = Settings.builder()
@@ -239,12 +239,12 @@ public void testExecuteAllocateUnassigned() throws Exception {
 
         IndexRoutingTable.Builder indexRoutingTable = IndexRoutingTable.builder(index)
             .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), "node1", true, ShardRoutingState.STARTED))
-            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 1), null, null, true, ShardRoutingState.UNASSIGNED,
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), null, null, false, ShardRoutingState.UNASSIGNED,
                 new UnassignedInfo(randomFrom(UnassignedInfo.Reason.values()), "the shard is intentionally unassigned")));
 
         CheckShrinkReadyStep step = createRandomInstance();
-        assertAllocateStatus(index, 2, 0, step, existingSettings, node1Settings, node2Settings, indexRoutingTable,
-            new ClusterStateWaitStep.Result(false, new CheckShrinkReadyStep.Info("", 2, -1)));
+        assertAllocateStatus(index, 1, 1, step, existingSettings, node1Settings, node2Settings, indexRoutingTable,
+            new ClusterStateWaitStep.Result(true, null));
     }
 
     /**
@@ -267,7 +267,9 @@ public void testExecuteAllocateUnassigned() throws Exception {
     public void testExecuteReplicasNotAllocatedOnSingleNode() {
         Index index = new Index(randomAlphaOfLengthBetween(1, 20), randomAlphaOfLengthBetween(1, 20));
         Map<String, String> requires = Collections.singletonMap("_id", "node1");
-        Settings.Builder existingSettings = Settings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT.id)
+        Settings.Builder existingSettings = Settings.builder()
+            .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT.id)
+            .put(IndexMetaData.INDEX_ROUTING_REQUIRE_GROUP_PREFIX + "._id", "node1")
             .put(IndexMetaData.SETTING_INDEX_UUID, index.getUUID());
         Settings.Builder expectedSettings = Settings.builder();
         Settings.Builder node1Settings = Settings.builder();
@@ -278,12 +280,40 @@ public void testExecuteReplicasNotAllocatedOnSingleNode() {
 
         IndexRoutingTable.Builder indexRoutingTable = IndexRoutingTable.builder(index)
             .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), "node1", true, ShardRoutingState.STARTED))
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 1), "node1", false, ShardRoutingState.STARTED))
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 1), "node2", true, ShardRoutingState.STARTED))
             .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), null, null, false, ShardRoutingState.UNASSIGNED,
                 new UnassignedInfo(UnassignedInfo.Reason.REPLICA_ADDED, "no attempt")));
 
         CheckShrinkReadyStep step = createRandomInstance();
-        assertAllocateStatus(index, 1, 1, step, existingSettings, node1Settings, node2Settings, indexRoutingTable,
-            new ClusterStateWaitStep.Result(false, new CheckShrinkReadyStep.Info("", 1, -1)));
+        assertAllocateStatus(index, 2, 1, step, existingSettings, node1Settings, node2Settings, indexRoutingTable,
+            new ClusterStateWaitStep.Result(true, null));
+    }
+
+    public void testExecuteReplicasButCopiesNotPresent() {
+        Index index = new Index(randomAlphaOfLengthBetween(1, 20), randomAlphaOfLengthBetween(1, 20));
+        Map<String, String> requires = Collections.singletonMap("_id", "node1");
+        Settings.Builder existingSettings = Settings.builder()
+            .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT.id)
+            .put(IndexMetaData.INDEX_ROUTING_REQUIRE_GROUP_PREFIX + "._id", "node1")
+            .put(IndexMetaData.SETTING_INDEX_UUID, index.getUUID());
+        Settings.Builder expectedSettings = Settings.builder();
+        Settings.Builder node1Settings = Settings.builder();
+        Settings.Builder node2Settings = Settings.builder();
+        requires.forEach((k, v) -> {
+            expectedSettings.put(IndexMetaData.INDEX_ROUTING_REQUIRE_GROUP_SETTING.getKey() + k, v);
+        });
+
+        IndexRoutingTable.Builder indexRoutingTable = IndexRoutingTable.builder(index)
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), "node1", true, ShardRoutingState.STARTED))
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 1), "node2", false, ShardRoutingState.STARTED))
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 1), "node3", true, ShardRoutingState.STARTED))
+            .addShard(TestShardRouting.newShardRouting(new ShardId(index, 0), null, null, false, ShardRoutingState.UNASSIGNED,
+                new UnassignedInfo(UnassignedInfo.Reason.REPLICA_ADDED, "no attempt")));
+
+        CheckShrinkReadyStep step = createRandomInstance();
+        assertAllocateStatus(index, 2, 1, step, existingSettings, node1Settings, node2Settings, indexRoutingTable,
+            new ClusterStateWaitStep.Result(false, new CheckShrinkReadyStep.Info("node1", 2, 1)));
     }
 
     public void testExecuteIndexMissing() throws Exception {