Fixing unblock condition for index create block

Signed-off-by: Rishav Sagar <rissag@amazon.com>

CHANGELOG.md

@@ -157,6 +157,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Fixed
 - Fix flaky ResourceAwareTasksTests.testBasicTaskResourceTracking test ([#8993](https://github.com/opensearch-project/OpenSearch/pull/8993))
 - Fix memory leak when using Zstd Dictionary ([#9403](https://github.com/opensearch-project/OpenSearch/pull/9403))
+- Fix condition to remove index create block ([#9437](https://github.com/opensearch-project/OpenSearch/pull/9437))
 
 ### Security
 

server/src/main/java/org/opensearch/cluster/routing/allocation/DiskThresholdMonitor.java

@@ -380,9 +380,17 @@ public void onNewInfo(ClusterInfo info) {
         if ((state.getBlocks().hasGlobalBlockWithId(Metadata.CLUSTER_CREATE_INDEX_BLOCK.id()) == false)
             && nodes.size() > 0
             && nodesOverHighThreshold.size() == nodes.size()) {
+            logger.warn(
+                "Enabling index create block on cluster as all nodes are breaching high disk watermark. "
+                    + "Number of nodes above high watermark: {}. Total numbers of node: {}.",
+                nodesOverHighThreshold.size(),
+                nodes.size()
+            );
             setIndexCreateBlock(listener, true);
         } else if (state.getBlocks().hasGlobalBlockWithId(Metadata.CLUSTER_CREATE_INDEX_BLOCK.id())
-            && diskThresholdSettings.isCreateIndexBlockAutoReleaseEnabled()) {
+            && diskThresholdSettings.isCreateIndexBlockAutoReleaseEnabled()
+            && nodesOverHighThreshold.size() < nodes.size()) {
+                logger.warn("Removing index create block on cluster as all nodes are no longer breaching high disk watermark.");
                 setIndexCreateBlock(listener, false);
             } else {
                 listener.onResponse(null);

server/src/test/java/org/opensearch/cluster/routing/allocation/DiskThresholdMonitorTests.java

@@ -55,10 +55,12 @@
 import org.opensearch.test.MockLogAppender;
 import org.opensearch.test.junit.annotations.TestLogging;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -67,6 +69,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.LongSupplier;
 
+import static org.opensearch.cluster.routing.allocation.DiskThresholdSettings.CLUSTER_CREATE_INDEX_BLOCK_AUTO_RELEASE;
 import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.equalTo;
 
@@ -581,12 +584,16 @@ protected void setIndexCreateBlock(ActionListener<Void> listener, boolean indexC
         );
 
         advanceTime.set(false); // will do one reroute and emit warnings, but subsequent reroutes and associated messages are delayed
-        assertSingleWarningMessage(
-            monitor,
-            aboveHighWatermark,
+        final List<String> messages = new ArrayList<>();
+        messages.add(
             "high disk watermark [90%] exceeded on * shards will be relocated away from this node* "
                 + "the node is expected to continue to exceed the high disk watermark when these relocations are complete"
         );
+        messages.add(
+            "Enabling index create block on cluster as all nodes are breaching high disk watermark. "
+                + "Number of nodes above high watermark: 1. Total numbers of node: 1."
+        );
+        assertMultipleWarningMessages(monitor, aboveHighWatermark, messages);
 
         advanceTime.set(true);
         assertRepeatedWarningMessages(
@@ -605,22 +612,11 @@ protected void setIndexCreateBlock(ActionListener<Void> listener, boolean indexC
 
         relocatingShardSizeRef.set(-5L);
         advanceTime.set(true);
-        assertSingleInfoMessage(
-            monitor,
-            aboveHighWatermark,
-            "high disk watermark [90%] exceeded on * shards will be relocated away from this node* "
-                + "the node is expected to be below the high disk watermark when these relocations are complete"
-        );
 
         relocatingShardSizeRef.set(0L);
         timeSupplier.getAsLong(); // advance time long enough to do another reroute
         advanceTime.set(false); // will do one reroute and emit warnings, but subsequent reroutes and associated messages are delayed
-        assertSingleWarningMessage(
-            monitor,
-            aboveHighWatermark,
-            "high disk watermark [90%] exceeded on * shards will be relocated away from this node* "
-                + "the node is expected to continue to exceed the high disk watermark when these relocations are complete"
-        );
+        assertMultipleWarningMessages(monitor, aboveHighWatermark, messages);
 
         advanceTime.set(true);
         assertRepeatedWarningMessages(
@@ -722,6 +718,113 @@ protected void setIndexCreateBlock(ActionListener<Void> listener, boolean indexC
         assertTrue(countBlocksCalled.get() == 0);
     }
 
+    public void testIndexCreateBlockRemovedOnlyWhenAnyNodeAboveHighWatermark() {
+        AllocationService allocation = createAllocationService(
+            Settings.builder()
+                .put("cluster.routing.allocation.node_concurrent_recoveries", 10)
+                .put("cluster.blocks.create_index.enabled", false)
+                .build()
+        );
+        Metadata metadata = Metadata.builder()
+            .put(
+                IndexMetadata.builder("test")
+                    .settings(settings(Version.CURRENT).put("index.routing.allocation.require._id", "node2"))
+                    .numberOfShards(1)
+                    .numberOfReplicas(0)
+            )
+            .put(
+                IndexMetadata.builder("test_1")
+                    .settings(settings(Version.CURRENT).put("index.routing.allocation.require._id", "node1"))
+                    .numberOfShards(1)
+                    .numberOfReplicas(0)
+            )
+            .put(
+                IndexMetadata.builder("test_2")
+                    .settings(settings(Version.CURRENT).put("index.routing.allocation.require._id", "node1"))
+                    .numberOfShards(1)
+                    .numberOfReplicas(0)
+            )
+            .build();
+        RoutingTable routingTable = RoutingTable.builder()
+            .addAsNew(metadata.index("test"))
+            .addAsNew(metadata.index("test_1"))
+            .addAsNew(metadata.index("test_2"))
+            .build();
+
+        final ClusterState clusterState = applyStartedShardsUntilNoChange(
+            ClusterState.builder(ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
+                .metadata(metadata)
+                .routingTable(routingTable)
+                .blocks(ClusterBlocks.builder().addGlobalBlock(Metadata.CLUSTER_CREATE_INDEX_BLOCK).build())
+                .nodes(DiscoveryNodes.builder().add(newNode("node1")).add(newNode("node2")))
+                .build(),
+            allocation
+        );
+        AtomicReference<Set<String>> indices = new AtomicReference<>();
+        AtomicInteger countBlocksCalled = new AtomicInteger();
+        AtomicInteger countUnblockBlocksCalled = new AtomicInteger();
+        AtomicLong currentTime = new AtomicLong();
+        Settings settings = Settings.builder().put(CLUSTER_CREATE_INDEX_BLOCK_AUTO_RELEASE.getKey(), true).build();
+        DiskThresholdMonitor monitor = new DiskThresholdMonitor(
+            settings,
+            () -> clusterState,
+            new ClusterSettings(settings, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS),
+            null,
+            currentTime::get,
+            (reason, priority, listener) -> {
+                listener.onResponse(null);
+            }
+        ) {
+
+            @Override
+            protected void updateIndicesReadOnly(Set<String> indicesToMarkReadOnly, ActionListener<Void> listener, boolean readOnly) {
+                assertTrue(indices.compareAndSet(null, indicesToMarkReadOnly));
+                assertTrue(readOnly);
+                listener.onResponse(null);
+            }
+
+            @Override
+            protected void setIndexCreateBlock(ActionListener<Void> listener, boolean indexCreateBlock) {
+                if (indexCreateBlock == true) {
+                    countBlocksCalled.set(countBlocksCalled.get() + 1);
+                } else {
+                    countUnblockBlocksCalled.set(countUnblockBlocksCalled.get() + 1);
+                }
+
+                listener.onResponse(null);
+            }
+        };
+
+        Map<String, DiskUsage> builder = new HashMap<>();
+
+        // Initially all the nodes are breaching high watermark and IndexCreateBlock is already present on the cluster.
+        // Since block is already present, DiskThresholdMonitor should not again try to apply block.
+        builder.put("node1", new DiskUsage("node1", "node1", "/foo/bar", 100, 9));
+        builder.put("node2", new DiskUsage("node2", "node2", "/foo/bar", 100, 9));
+        monitor.onNewInfo(clusterInfo(builder));
+        // Since Block is already present and nodes are below high watermark so neither block nor unblock will be called.
+        assertEquals(countBlocksCalled.get(), 0);
+        assertEquals(countUnblockBlocksCalled.get(), 0);
+
+        // Ensure DiskThresholdMonitor does not try to remove block in the next iteration if all nodes are breaching high watermark.
+        monitor.onNewInfo(clusterInfo(builder));
+        assertEquals(countBlocksCalled.get(), 0);
+        assertEquals(countUnblockBlocksCalled.get(), 0);
+
+        builder = new HashMap<>();
+
+        // If any node is no longer breaching high watermark, DiskThresholdMonitor should remove IndexCreateBlock.
+        builder.put("node1", new DiskUsage("node1", "node1", "/foo/bar", 100, 19));
+        builder.put("node2", new DiskUsage("node2", "node2", "/foo/bar", 100, 1));
+        // Need to add delay in current time to allow nodes to be removed high watermark list.
+        currentTime.addAndGet(randomLongBetween(60001, 120000));
+
+        monitor.onNewInfo(clusterInfo(builder));
+        // Block will be removed if any nodes is no longer breaching high watermark.
+        assertEquals(countBlocksCalled.get(), 0);
+        assertEquals(countUnblockBlocksCalled.get(), 1);
+    }
+
     private void assertNoLogging(DiskThresholdMonitor monitor, final Map<String, DiskUsage> diskUsages) throws IllegalAccessException {
         try (MockLogAppender mockAppender = MockLogAppender.createForLoggers(LogManager.getLogger(DiskThresholdMonitor.class))) {
             mockAppender.addExpectation(
@@ -756,10 +859,11 @@ private void assertRepeatedWarningMessages(DiskThresholdMonitor monitor, final M
         }
     }
 
-    private void assertSingleWarningMessage(DiskThresholdMonitor monitor, final Map<String, DiskUsage> diskUsages, String message)
+    private void assertMultipleWarningMessages(DiskThresholdMonitor monitor, final Map<String, DiskUsage> diskUsages, List<String> messages)
         throws IllegalAccessException {
-        assertLogging(monitor, diskUsages, Level.WARN, message);
-        assertNoLogging(monitor, diskUsages);
+        for (int index = 0; index < messages.size(); index++) {
+            assertLogging(monitor, diskUsages, Level.WARN, messages.get(index));
+        }
     }
 
     private void assertSingleInfoMessage(DiskThresholdMonitor monitor, final Map<String, DiskUsage> diskUsages, String message)