draft PR to fix cluster not able to spin up issue when disk usage exceeds threshold

Signed-off-by: zane-neo <zaniu@amazon.com>

Author: zane-neo

server/src/main/java/org/opensearch/cluster/InternalClusterInfoService.java

@@ -155,13 +155,17 @@ void setUpdateFrequency(TimeValue updateFrequency) {
 
     @Override
     public void clusterChanged(ClusterChangedEvent event) {
-        if (event.localNodeClusterManager() && refreshAndRescheduleRunnable.get() == null) {
-            logger.trace("elected as cluster-manager, scheduling cluster info update tasks");
-            executeRefresh(event.state(), "became cluster-manager");
-
-            final RefreshAndRescheduleRunnable newRunnable = new RefreshAndRescheduleRunnable();
-            refreshAndRescheduleRunnable.set(newRunnable);
-            threadPool.scheduleUnlessShuttingDown(updateFrequency, REFRESH_EXECUTOR, newRunnable);
+        if (event.localNodeClusterManager()) {
+            if (!event.state().blocks().indices().isEmpty()) {
+                executeRefreshImmediately(event.state());
+            } else if (refreshAndRescheduleRunnable.get() == null) {
+                logger.trace("elected as cluster-manager, scheduling cluster info update tasks");
+                executeRefresh(event.state(), "became cluster-manager");
+
+                final RefreshAndRescheduleRunnable newRunnable = new RefreshAndRescheduleRunnable();
+                refreshAndRescheduleRunnable.set(newRunnable);
+                threadPool.scheduleUnlessShuttingDown(updateFrequency, REFRESH_EXECUTOR, newRunnable);
+            }
         } else if (event.localNodeClusterManager() == false) {
             refreshAndRescheduleRunnable.set(null);
             return;
@@ -204,6 +208,14 @@ private void executeRefresh(ClusterState clusterState, String reason) {
         }
     }
 
+    private void executeRefreshImmediately(ClusterState clusterState) {
+        String reason = "became cluster-manager with indices blocked";
+        if (!clusterState.nodes().getDataNodes().isEmpty()) {
+            logger.trace("refreshing cluster info immediately [{}]", reason);
+            new RefreshRunnable(reason).run();
+        }
+    }
+
     @Override
     public ClusterInfo getClusterInfo() {
         final IndicesStatsSummary indicesStatsSummary = this.indicesStatsSummary; // single volatile read

server/src/main/java/org/opensearch/cluster/block/ClusterBlocks.java

@@ -67,9 +67,9 @@ public class ClusterBlocks extends AbstractDiffable<ClusterBlocks> {
 
     private final Set<ClusterBlock> global;
 
-    private final Map<String, Set<ClusterBlock>> indicesBlocks;
+    private Map<String, Set<ClusterBlock>> indicesBlocks;
 
-    private final EnumMap<ClusterBlockLevel, ImmutableLevelHolder> levelHolders;
+    private EnumMap<ClusterBlockLevel, ImmutableLevelHolder> levelHolders;
 
     ClusterBlocks(Set<ClusterBlock> global, final Map<String, Set<ClusterBlock>> indicesBlocks) {
         this.global = global;
@@ -161,6 +161,24 @@ public boolean hasIndexBlock(String index, ClusterBlock block) {
         return indicesBlocks.containsKey(index) && indicesBlocks.get(index).contains(block);
     }
 
+    public void removeIndexBlock(String index, ClusterBlock block) {
+        Map<String, Set<ClusterBlock>> newIndicesBlocks = new HashMap<>(indicesBlocks); // copy to avoid UnsupportedOperationException>
+        for (Map.Entry<String, Set<ClusterBlock>> entry : indicesBlocks.entrySet()) {
+            String indexName = entry.getKey();
+            Set<ClusterBlock> clusterBlockSet = new HashSet<>(entry.getValue());
+            if (indexName.equals(index)) {
+                clusterBlockSet.remove(block);
+                if (clusterBlockSet.isEmpty()) {
+                    newIndicesBlocks.remove(indexName);
+                } else {
+                    newIndicesBlocks.put(indexName, Collections.unmodifiableSet(clusterBlockSet));
+                }
+            }
+        }
+        this.indicesBlocks = Collections.unmodifiableMap(newIndicesBlocks);
+        this.levelHolders = generateLevelHolders(global, indicesBlocks);
+    }
+
     public boolean hasIndexBlockWithId(String index, int blockId) {
         final Set<ClusterBlock> clusterBlocks = indicesBlocks.get(index);
         if (clusterBlocks != null) {

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

@@ -40,7 +40,9 @@
 import org.opensearch.cluster.ClusterInfo;
 import org.opensearch.cluster.ClusterState;
 import org.opensearch.cluster.DiskUsage;
+import org.opensearch.cluster.block.ClusterBlock;
 import org.opensearch.cluster.block.ClusterBlockLevel;
+import org.opensearch.cluster.block.ClusterBlocks;
 import org.opensearch.cluster.metadata.IndexMetadata;
 import org.opensearch.cluster.metadata.Metadata;
 import org.opensearch.cluster.routing.RerouteService;
@@ -253,6 +255,9 @@ public void onNewInfo(ClusterInfo info) {
                     }
 
                 } else {
+                    for (Map.Entry<String, Set<ClusterBlock>> indexBlockEntry : state.blocks().indices().entrySet()) {
+                        state.blocks().removeIndexBlock(indexBlockEntry.getKey(), IndexMetadata.INDEX_READ_ONLY_ALLOW_DELETE_BLOCK);
+                    }
 
                     nodesOverHighThresholdAndRelocating.remove(node);