Add FailedShardEntry info to shard-failed task source string

docs/changelog/125520.yaml

@@ -0,0 +1,6 @@
+pr: 125520
+summary: Add `FailedShardEntry` info to shard-failed task source string
+area: Allocation
+type: enhancement
+issues:
+ - 102606

server/src/internalClusterTest/java/org/elasticsearch/cluster/routing/allocation/ShardStateIT.java

@@ -8,14 +8,21 @@
  */
 package org.elasticsearch.cluster.routing.allocation;
 
+import org.elasticsearch.ElasticsearchException;
+import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.health.ClusterHealthStatus;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
+import org.elasticsearch.cluster.metadata.Metadata;
+import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.Priority;
 import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.test.ESIntegTestCase;
 
+import java.util.concurrent.CyclicBarrier;
+
 import static org.hamcrest.Matchers.equalTo;
 
 public class ShardStateIT extends ESIntegTestCase {
@@ -76,4 +83,58 @@ protected void assertPrimaryTerms(long shard0Term, long shard1Term) {
             }
         }
     }
+
+    public void testGetPendingTasksSourceStringDataForFailedShard() throws Exception {
+        internalCluster().ensureAtLeastNumDataNodes(1);
+        prepareCreate("test").setSettings(indexSettings(1, 0)).get();
+        ensureGreen();
+
+        final var masterNodeClusterService = internalCluster().getCurrentMasterNodeInstance(ClusterService.class);
+        final var barrier = new CyclicBarrier(2);
+
+        // Used to block the master service task processing so we have a chance to get the pending shard-failed task.
+        masterNodeClusterService.createTaskQueue("initial-block", Priority.NORMAL, batchExecutionContext -> {
+            safeAwait(barrier);
+            safeAwait(barrier);
+            batchExecutionContext.taskContexts().forEach(c -> c.success(() -> {}));
+            return batchExecutionContext.initialState();
+        }).submitTask("initial-block", e -> fail(e, "unexpected"), null);
+
+        // Sync up with the blocking executor.
+        safeAwait(barrier);
+
+        // Obtain a reference to the IndexShard for shard 0.
+        final var state = masterNodeClusterService.state();
+        final var shard0RoutingTable = state.routingTable(Metadata.DEFAULT_PROJECT_ID).index("test").shard(0);
+        assertNotNull(shard0RoutingTable);
+        final var nodeId = shard0RoutingTable.primaryShard().currentNodeId();
+        final var node = state.nodes().get(nodeId).getName();
+        final var indicesService = internalCluster().getInstance(IndicesService.class, node);
+        final var shard0 = indicesService.indexService(resolveIndex("test")).getShard(0);
+        assertNotNull(shard0);
+
+        // Create a failed shard state action for shard 0.
+        final var shardFailedReason = "simulated test failure";
+        final var shardFailedException = new ElasticsearchException("simulated exception");
+        shard0.failShard(shardFailedReason, shardFailedException);
+
+        // Get the pending tasks and verify we see the shard-failed state action and expected source string components.
+        final var masterService = masterNodeClusterService.getMasterService();
+        assertBusy(() -> {
+            assertTrue(masterService.pendingTasks().stream().anyMatch(task -> {
+                final var src = task.getSource().string();
+                // We expect the failure reason and exception message, but not the stack trace.
+                return src.startsWith("shard-failed ")
+                    && src.contains("[test][0]")
+                    && src.contains(shardFailedReason)
+                    && src.contains(shardFailedException.getMessage())
+                    && src.contains(ExceptionsHelper.stackTrace(shardFailedException)) == false;
+            }));
+        });
+
+        // Unblock the master service from the executor above.
+        safeAwait(barrier);
+        // Wait for the failed shard task to get processed and then for the shard and cluster to recover.
+        ensureGreen();
+    }
 }

server/src/main/java/org/elasticsearch/cluster/action/shard/ShardStateAction.java

@@ -283,16 +283,14 @@ private static class ShardFailedTransportHandler implements TransportRequestHand
             ClusterService clusterService,
             ShardFailedClusterStateTaskExecutor shardFailedClusterStateTaskExecutor
         ) {
-            taskQueue = clusterService.createTaskQueue(TASK_SOURCE, Priority.HIGH, shardFailedClusterStateTaskExecutor);
+            taskQueue = clusterService.createTaskQueue("shard-failed", Priority.HIGH, shardFailedClusterStateTaskExecutor);
         }
 
-        private static final String TASK_SOURCE = "shard-failed";
-
         @Override
         public void messageReceived(FailedShardEntry request, TransportChannel channel, Task task) {
             logger.debug(() -> format("%s received shard failed for [%s]", request.getShardId(), request), request.failure);
             taskQueue.submitTask(
-                TASK_SOURCE,
+                "shard-failed " + request.toStringNoFailureStackTrace(),
                 new FailedShardUpdateTask(request, new ChannelActionListener<>(channel).map(ignored -> TransportResponse.Empty.INSTANCE)),
                 null
             );
@@ -501,14 +499,22 @@ public void writeTo(StreamOutput out) throws IOException {
 
         @Override
         public String toString() {
+            return toString(true);
+        }
+
+        public String toStringNoFailureStackTrace() {
+            return toString(false);
+        }
+
+        private String toString(boolean includeStackTrace) {
             return Strings.format(
                 "FailedShardEntry{shardId [%s], allocationId [%s], primary term [%d], message [%s], markAsStale [%b], failure [%s]}",
                 shardId,
                 allocationId,
                 primaryTerm,
                 message,
                 markAsStale,
-                failure != null ? ExceptionsHelper.stackTrace(failure) : null
+                failure == null ? null : (includeStackTrace ? ExceptionsHelper.stackTrace(failure) : failure.getMessage())
             );
         }