Small cleanup in PRTS#doRecovery (#93549)

Renames `failureHandler` to `cleanupOnly` and makes use of
`ActionListener#run` where appropriate.

Author: DaveCTurner

server/src/main/java/org/elasticsearch/indices/recovery/PeerRecoveryTargetService.java

@@ -222,7 +222,8 @@ private void doRecovery(final long recoveryId, final StartRecoveryRequest preExi
         final IndexShard indexShard = recoveryTarget.indexShard();
         final Releasable onCompletion = Releasables.wrap(recoveryTarget.disableRecoveryMonitor(), recoveryRef);
 
-        final var failureHandler = ActionListener.notifyOnce(ActionListener.runBefore(ActionListener.noop().delegateResponse((l, e) -> {
+        // async version of the catch/finally structure we need, but this does nothing with successes so needs further modification below
+        final var cleanupOnly = ActionListener.notifyOnce(ActionListener.runBefore(ActionListener.noop().delegateResponse((l, e) -> {
             // this will be logged as warning later on...
             logger.trace("unexpected error while preparing shard for peer recovery, failing recovery", e);
             onGoingRecoveries.failRecovery(
@@ -235,28 +236,23 @@ private void doRecovery(final long recoveryId, final StartRecoveryRequest preExi
         if (indexShard.routingEntry().isPromotableToPrimary() == false) {
             assert preExistingRequest == null;
             assert indexShard.indexSettings().getIndexMetadata().isSearchableSnapshot() == false;
-            try {
-                indexShard.preRecovery(failureHandler.map(v -> {
-                    logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());
-                    indexShard.prepareForIndexRecovery();
-                    // Skip unnecessary intermediate stages
-                    recoveryState.setStage(RecoveryState.Stage.VERIFY_INDEX);
-                    recoveryState.setStage(RecoveryState.Stage.TRANSLOG);
-                    indexShard.openEngineAndSkipTranslogRecovery();
-                    recoveryState.getIndex().setFileDetailsComplete();
-                    recoveryState.setStage(RecoveryState.Stage.FINALIZE);
-                    onGoingRecoveries.markRecoveryAsDone(recoveryId);
-                    return null;
-                }));
-            } catch (Exception e) {
-                failureHandler.onFailure(e);
-            }
-
+            ActionListener.run(cleanupOnly.map(v -> {
+                logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());
+                indexShard.prepareForIndexRecovery();
+                // Skip unnecessary intermediate stages
+                recoveryState.setStage(RecoveryState.Stage.VERIFY_INDEX);
+                recoveryState.setStage(RecoveryState.Stage.TRANSLOG);
+                indexShard.openEngineAndSkipTranslogRecovery();
+                recoveryState.getIndex().setFileDetailsComplete();
+                recoveryState.setStage(RecoveryState.Stage.FINALIZE);
+                onGoingRecoveries.markRecoveryAsDone(recoveryId);
+                return null;
+            }), indexShard::preRecovery);
             return;
         }
 
         record StartRecoveryRequestToSend(StartRecoveryRequest startRecoveryRequest, String actionName, TransportRequest requestToSend) {}
-        final ActionListener<StartRecoveryRequestToSend> toSendListener = failureHandler.map(r -> {
+        final ActionListener<StartRecoveryRequestToSend> toSendListener = cleanupOnly.map(r -> {
             logger.trace(
                 "{} [{}]: recovery from {}",
                 r.startRecoveryRequest().shardId(),
@@ -273,30 +269,26 @@ record StartRecoveryRequestToSend(StartRecoveryRequest startRecoveryRequest, Str
         });
 
         if (preExistingRequest == null) {
-            try {
-                indexShard.preRecovery(toSendListener.delegateFailure((l, v) -> ActionListener.completeWith(l, () -> {
-                    logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());
-                    indexShard.prepareForIndexRecovery();
-                    if (indexShard.indexSettings().getIndexMetadata().isSearchableSnapshot()) {
-                        // for searchable snapshots, peer recovery is treated similarly to recovery from snapshot
-                        indexShard.getIndexEventListener().afterFilesRestoredFromRepository(indexShard);
-                        final Store store = indexShard.store();
-                        store.incRef();
-                        try {
-                            StoreRecovery.bootstrap(indexShard, store);
-                        } finally {
-                            store.decRef();
-                        }
+            ActionListener.run(toSendListener.map(v -> {
+                logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());
+                indexShard.prepareForIndexRecovery();
+                if (indexShard.indexSettings().getIndexMetadata().isSearchableSnapshot()) {
+                    // for searchable snapshots, peer recovery is treated similarly to recovery from snapshot
+                    indexShard.getIndexEventListener().afterFilesRestoredFromRepository(indexShard);
+                    final Store store = indexShard.store();
+                    store.incRef();
+                    try {
+                        StoreRecovery.bootstrap(indexShard, store);
+                    } finally {
+                        store.decRef();
                     }
-                    final long startingSeqNo = indexShard.recoverLocallyUpToGlobalCheckpoint();
-                    assert startingSeqNo == UNASSIGNED_SEQ_NO || recoveryTarget.state().getStage() == RecoveryState.Stage.TRANSLOG
-                        : "unexpected recovery stage [" + recoveryTarget.state().getStage() + "] starting seqno [ " + startingSeqNo + "]";
-                    final var startRequest = getStartRecoveryRequest(logger, clusterService.localNode(), recoveryTarget, startingSeqNo);
-                    return new StartRecoveryRequestToSend(startRequest, PeerRecoverySourceService.Actions.START_RECOVERY, startRequest);
-                })));
-            } catch (Exception e) {
-                toSendListener.onFailure(e);
-            }
+                }
+                final long startingSeqNo = indexShard.recoverLocallyUpToGlobalCheckpoint();
+                assert startingSeqNo == UNASSIGNED_SEQ_NO || recoveryTarget.state().getStage() == RecoveryState.Stage.TRANSLOG
+                    : "unexpected recovery stage [" + recoveryTarget.state().getStage() + "] starting seqno [ " + startingSeqNo + "]";
+                final var startRequest = getStartRecoveryRequest(logger, clusterService.localNode(), recoveryTarget, startingSeqNo);
+                return new StartRecoveryRequestToSend(startRequest, PeerRecoverySourceService.Actions.START_RECOVERY, startRequest);
+            }), indexShard::preRecovery);
         } else {
             toSendListener.onResponse(
                 new StartRecoveryRequestToSend(