Make BackgroundIndexer more Efficient (#57781) (#57789)

Improve efficiency of background indexer by allowing to add
an assertion for failures while they are produced to prevent
queuing them up.
Also, add non-blocking stop to the background indexer so that when
stopping multiple indexers we don't needlessly continue indexing
on some indexers while stopping another one.

Closes #57766

server/src/internalClusterTest/java/org/elasticsearch/discovery/DiskDisruptionIT.java

@@ -137,7 +137,7 @@ public class DiskDisruptionIT extends AbstractDisruptionTestCase {
             false, random())) {
             indexer.setRequestTimeout(TimeValue.ZERO);
             indexer.setIgnoreIndexingFailures(true);
-            indexer.setAssertNoFailuresOnStop(false);
+            indexer.setFailureAssertion(e -> {});
             indexer.start(-1);
 
             waitForDocs(randomIntBetween(1, 100), indexer);

server/src/internalClusterTest/java/org/elasticsearch/indices/state/CloseIndexIT.java

@@ -201,19 +201,12 @@ public class CloseIndexIT extends ESIntegTestCase {
 
         int nbDocs = 0;
         try (BackgroundIndexer indexer = new BackgroundIndexer(indexName, "_doc", client(), MAX_DOCS)) {
-            indexer.setAssertNoFailuresOnStop(false);
+            indexer.setFailureAssertion(t -> assertException(t, indexName));
 
             waitForDocs(randomIntBetween(10, 50), indexer);
             assertBusy(() -> closeIndices(indexName));
-            indexer.stop();
+            indexer.stopAndAwaitStopped();
             nbDocs += indexer.totalIndexedDocs();
-
-            final Throwable[] failures = indexer.getFailures();
-            if (failures != null) {
-                for (Throwable failure : failures) {
-                    assertException(failure, indexName);
-                }
-            }
         }
 
         assertIndexIsClosed(indexName);
@@ -280,6 +273,7 @@ public class CloseIndexIT extends ESIntegTestCase {
         createIndex(indexName);
 
         final BackgroundIndexer indexer = new BackgroundIndexer(indexName, "_doc", client(), MAX_DOCS);
+        indexer.setFailureAssertion(e -> {});
         waitForDocs(1, indexer);
 
         final CountDownLatch latch = new CountDownLatch(1);
@@ -321,8 +315,7 @@ public class CloseIndexIT extends ESIntegTestCase {
             thread.join();
         }
 
-        indexer.setAssertNoFailuresOnStop(false);
+        indexer.stopAndAwaitStopped();
-        indexer.stop();
 
         final ClusterState clusterState = client().admin().cluster().prepareState().get().getState();
         if (clusterState.metadata().indices().get(indexName).getState() == IndexMetadata.State.CLOSE) {

server/src/internalClusterTest/java/org/elasticsearch/indices/state/CloseWhileRelocatingShardsIT.java

@@ -112,6 +112,7 @@ public class CloseWhileRelocatingShardsIT extends ESIntegTestCase {
                     logger.debug("creating index {} with background indexing", indexName);
                     final BackgroundIndexer indexer = new BackgroundIndexer(indexName, "_doc", client(), -1, 1);
                     indexers.put(indexName, indexer);
+                    indexer.setFailureAssertion(t -> assertException(t, indexName));
                     waitForDocs(1, indexer);
             }
             docsPerIndex.put(indexName, (long) nbDocs);
@@ -225,20 +226,15 @@ public class CloseWhileRelocatingShardsIT extends ESIntegTestCase {
                 thread.join();
             }
 
+            // stop indexers first without waiting for stop to not redundantly index on some while waiting for another one to stop
+            for (BackgroundIndexer indexer : indexers.values()) {
+                indexer.stop();
+            }
             for (Map.Entry<String, BackgroundIndexer> entry : indexers.entrySet()) {
                 final BackgroundIndexer indexer = entry.getValue();
-                indexer.setAssertNoFailuresOnStop(false);
+                indexer.awaitStopped();
-                indexer.stop();
-
                 final String indexName = entry.getKey();
                 docsPerIndex.computeIfPresent(indexName, (key, value) -> value + indexer.totalIndexedDocs());
-
-                final Throwable[] failures = indexer.getFailures();
-                if (failures != null) {
-                    for (Throwable failure : failures) {
-                        assertException(failure, indexName);
-                    }
-                }
             }
 
             for (String index : indices) {

server/src/internalClusterTest/java/org/elasticsearch/recovery/RecoveryWhileUnderLoadIT.java

@@ -128,7 +128,7 @@ public class RecoveryWhileUnderLoadIT extends ESIntegTestCase {
             logger.info("--> {} docs indexed", totalNumDocs);
 
             logger.info("--> marking and waiting for indexing threads to stop ...");
-            indexer.stop();
+            indexer.stopAndAwaitStopped();
             logger.info("--> indexing threads stopped");
 
             logger.info("--> refreshing the index");
@@ -183,7 +183,7 @@ public class RecoveryWhileUnderLoadIT extends ESIntegTestCase {
             logger.info("--> {} docs indexed", totalNumDocs);
 
             logger.info("--> marking and waiting for indexing threads to stop ...");
-            indexer.stop();
+            indexer.stopAndAwaitStopped();
             logger.info("--> indexing threads stopped");
 
             logger.info("--> refreshing the index");
@@ -261,7 +261,7 @@ public class RecoveryWhileUnderLoadIT extends ESIntegTestCase {
                     .setWaitForNoRelocatingShards(true));
 
             logger.info("--> marking and waiting for indexing threads to stop ...");
-            indexer.stop();
+            indexer.stopAndAwaitStopped();
             logger.info("--> indexing threads stopped");
 
             assertNoTimeout(client().admin().cluster().prepareHealth()
@@ -302,7 +302,7 @@ public class RecoveryWhileUnderLoadIT extends ESIntegTestCase {
             }
 
             logger.info("--> marking and waiting for indexing threads to stop ...");
-            indexer.stop();
+            indexer.stopAndAwaitStopped();
 
             logger.info("--> indexing threads stopped");
             logger.info("--> bump up number of replicas to 1 and allow all nodes to hold the index");

server/src/internalClusterTest/java/org/elasticsearch/recovery/RelocationIT.java

@@ -236,7 +236,7 @@ public class RelocationIT extends ESIntegTestCase {
             }
             logger.info("--> done relocations");
             logger.info("--> waiting for indexing threads to stop ...");
-            indexer.stop();
+            indexer.stopAndAwaitStopped();
             logger.info("--> indexing threads stopped");
 
             logger.info("--> refreshing the index");

test/framework/src/main/java/org/elasticsearch/test/BackgroundIndexer.java

@@ -39,14 +39,16 @@ import org.elasticsearch.common.xcontent.XContentFactory;
 import org.junit.Assert;
 
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Random;
 import java.util.Set;
-import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.Consumer;
 
 import static org.hamcrest.Matchers.emptyIterable;
 import static org.hamcrest.Matchers.equalTo;
@@ -58,7 +60,7 @@ public class BackgroundIndexer implements AutoCloseable {
     final Thread[] writers;
     final Client client;
     final CountDownLatch stopLatch;
-    final CopyOnWriteArrayList<Exception> failures;
+    final Collection<Exception> failures = new ArrayList<>();
     final AtomicBoolean stop = new AtomicBoolean(false);
     final AtomicLong idGenerator = new AtomicLong();
     final CountDownLatch startLatch = new CountDownLatch(1);
@@ -66,7 +68,7 @@ public class BackgroundIndexer implements AutoCloseable {
     final Semaphore availableBudget = new Semaphore(0);
     final boolean useAutoGeneratedIDs;
     private final Set<String> ids = ConcurrentCollections.newConcurrentSet();
-    private boolean assertNoFailuresOnStop = true;
+    private volatile Consumer<Exception> failureAssertion = null;
 
     volatile int minFieldSize = 10;
     volatile int maxFieldSize = 140;
@@ -118,7 +120,6 @@ public class BackgroundIndexer implements AutoCloseable {
         }
         this.client = client;
         useAutoGeneratedIDs = random.nextBoolean();
-        failures = new CopyOnWriteArrayList<>();
         writers = new Thread[writerCount];
         stopLatch = new CountDownLatch(writers.length);
         logger.info("--> creating {} indexing threads (auto start: [{}], numOfDocs: [{}])", writerCount, autoStart, numOfDocs);
@@ -162,7 +163,7 @@ public class BackgroundIndexer implements AutoCloseable {
                                             boolean add = ids.add(bulkItemResponse.getId());
                                             assert add : "ID: " + bulkItemResponse.getId() + " already used";
                                         } else {
-                                            failures.add(bulkItemResponse.getFailure().getCause());
+                                            trackFailure(bulkItemResponse.getFailure().getCause());
                                         }
                                     }
                                 } catch (Exception e) {
@@ -204,7 +205,7 @@ public class BackgroundIndexer implements AutoCloseable {
                         }
                         logger.info("**** done indexing thread {}  stop: {} numDocsIndexed: {}", indexerId, stop.get(), ids.size());
                     } catch (Exception e) {
-                        failures.add(e);
+                        trackFailure(e);
                         final long docId = id;
                         logger.warn(
                             (Supplier<?>)
@@ -222,6 +223,16 @@ public class BackgroundIndexer implements AutoCloseable {
         }
     }
 
+    private void trackFailure(Exception e) {
+        synchronized (failures) {
+            if (failureAssertion != null) {
+                failureAssertion.accept(e);
+            } else {
+                failures.add(e);
+            }
+        }
+    }
+
     private XContentBuilder generateSource(long id, Random random) throws IOException {
         int contentLength = RandomNumbers.randomIntBetween(random, minFieldSize, maxFieldSize);
         StringBuilder text = new StringBuilder(contentLength);
@@ -287,32 +298,55 @@ public class BackgroundIndexer implements AutoCloseable {
         setBudget(numOfDocs);
     }
 
-    /** Stop all background threads * */
+    /** Stop all background threads but don't wait for ongoing indexing operations to finish * */
-    public void stop() throws InterruptedException {
+    public void stop() {
-        if (stop.get()) {
-            return;
-        }
         stop.set(true);
+    }
+
+    public void awaitStopped() throws InterruptedException {
+        assert stop.get();
         Assert.assertThat("timeout while waiting for indexing threads to stop", stopLatch.await(6, TimeUnit.MINUTES), equalTo(true));
-        if (assertNoFailuresOnStop) {
+        if (failureAssertion == null) {
             assertNoFailures();
         }
     }
 
+    /** Stop all background threads and wait for ongoing indexing operations to finish * */
+    public void stopAndAwaitStopped() throws InterruptedException {
+        stop();
+        awaitStopped();
+    }
+
     public long totalIndexedDocs() {
         return ids.size();
     }
 
-    public Throwable[] getFailures() {
-        return failures.toArray(new Throwable[failures.size()]);
-    }
-
     public void assertNoFailures() {
+        synchronized (failures) {
             Assert.assertThat(failures, emptyIterable());
         }
+    }
 
-    public void setAssertNoFailuresOnStop(final boolean assertNoFailuresOnStop) {
+    /**
-        this.assertNoFailuresOnStop = assertNoFailuresOnStop;
+     * Set a consumer that can be used to run assertions on failures during indexing. If such a consumer is set then it disables adding
+     * failures to {@link #failures}. Should be used if the number of expected failures during indexing could become very large.
+     */
+    public void setFailureAssertion(Consumer<Exception> failureAssertion) {
+        synchronized (failures) {
+            this.failureAssertion = failureAssertion;
+            boolean success = false;
+            try {
+                for (Exception failure : failures) {
+                    failureAssertion.accept(failure);
+                }
+                failures.clear();
+                success = true;
+            } finally {
+                if (success == false) {
+                    stop();
+                }
+            }
+        }
     }
 
     @Override