Force merges to not happen when indexing a doc / flush

Today, even though our merge policy doesn't return new merge specs on SEGMENT_FLUSH, merge on the scheduler is still called on flush time, and can cause merges to stall indexing during merges. Both for the concurrent merge scheduler (the default) and the serial merge scheduler. This behavior become worse when throttling kicks in (today at 20mb per sec).

In order to solve it (outside of Lucene for now), we wrap the merge scheduler with an EnableMergeScheduler, where, on the thread level, using a thread local, the call to merge can be enabled/disabled.

A Merges helper class is added where all explicit merges operations should go through. If the scheduler is the enabled one, it will enable merges before calling the relevant explicit method call. In order to make sure Merges is the only class that calls the explicit merge calls, the IW variant of them is added to the forbidden APIs list.

closes #5319

core-signatures.txt

@@ -24,3 +24,9 @@ org.apache.lucene.util.RamUsageEstimator#sizeOf(java.lang.Object) @ This can be
 org.apache.lucene.index.IndexReader#decRef()
 org.apache.lucene.index.IndexReader#incRef()
 org.apache.lucene.index.IndexReader#tryIncRef()
+
+org.apache.lucene.index.IndexWriter#maybeMerge() @ use Merges#maybeMerge
+org.apache.lucene.index.IndexWriter#forceMerge(int) @ use Merges#forceMerge
+org.apache.lucene.index.IndexWriter#forceMerge(int,boolean) @ use Merges#forceMerge
+org.apache.lucene.index.IndexWriter#forceMergeDeletes() @ use Merges#forceMergeDeletes
+org.apache.lucene.index.IndexWriter#forceMergeDeletes(boolean) @ use Merges#forceMergeDeletes

pom.xml

@@ -990,6 +990,7 @@
                                 <exclude>org/apache/lucene/search/XReferenceManager.class</exclude>
                                 <exclude>org/apache/lucene/search/XSearcherManager.class</exclude>
                                 <exclude>org/elasticsearch/index/percolator/stats/ShardPercolateService$RamEstimator.class</exclude>
+                                <exclude>org/elasticsearch/index/merge/Merges.class</exclude>
                                 <!-- end excludes for valid system-out -->
                                 <!-- start excludes for Unsafe -->
                                 <exclude>org/elasticsearch/common/util/UnsafeUtils.class</exclude>

src/main/java/org/elasticsearch/index/engine/internal/InternalEngine.java

@@ -56,6 +56,7 @@ import org.elasticsearch.index.deletionpolicy.SnapshotIndexCommit;
 import org.elasticsearch.index.engine.*;
 import org.elasticsearch.index.indexing.ShardIndexingService;
 import org.elasticsearch.index.mapper.Uid;
+import org.elasticsearch.index.merge.Merges;
 import org.elasticsearch.index.merge.OnGoingMerge;
 import org.elasticsearch.index.merge.policy.IndexUpgraderMergePolicy;
 import org.elasticsearch.index.merge.policy.MergePolicyProvider;
@@ -947,7 +948,7 @@ public class InternalEngine extends AbstractIndexShardComponent implements Engin
         rwl.readLock().lock();
         try {
             ensureOpen();
-            indexWriter.maybeMerge();
+            Merges.maybeMerge(indexWriter);
         } catch (OutOfMemoryError e) {
             failEngine(e);
             throw new OptimizeFailedEngineException(shardId, e);
@@ -973,12 +974,12 @@ public class InternalEngine extends AbstractIndexShardComponent implements Engin
             try {
                 ensureOpen();
                 if (optimize.onlyExpungeDeletes()) {
-                    indexWriter.forceMergeDeletes(false);
+                    Merges.forceMergeDeletes(indexWriter, false);
                 } else if (optimize.maxNumSegments() <= 0) {
-                    indexWriter.maybeMerge();
+                    Merges.maybeMerge(indexWriter);
                     possibleMergeNeeded = false;
                 } else {
-                    indexWriter.forceMerge(optimize.maxNumSegments(), false);
+                    Merges.forceMerge(indexWriter, optimize.maxNumSegments(), false);
                 }
             } catch (OutOfMemoryError e) {
                 failEngine(e);

src/main/java/org/elasticsearch/index/merge/EnableMergeScheduler.java

@@ -0,0 +1,86 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.merge;
+
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.index.MergeScheduler;
+
+import java.io.IOException;
+
+/**
+ * A wrapper of another {@link org.apache.lucene.index.MergeScheduler} that allows
+ * to explicitly enable merge and disable on a thread local basis. The default is
+ * to have merges disabled.
+ * <p/>
+ * This merge scheduler can be used to get around the fact that even though a merge
+ * policy can control that no new merges will be created as a result of a segment flush
+ * (during indexing operation for example), the {@link #merge(org.apache.lucene.index.IndexWriter)}
+ * call will still be called, and can result in stalling indexing.
+ */
+public class EnableMergeScheduler extends MergeScheduler {
+
+    private final MergeScheduler mergeScheduler;
+
+    private final ThreadLocal<Boolean> enabled = new ThreadLocal<Boolean>() {
+        @Override
+        protected Boolean initialValue() {
+            return Boolean.FALSE;
+        }
+    };
+
+    public EnableMergeScheduler(MergeScheduler mergeScheduler) {
+        this.mergeScheduler = mergeScheduler;
+    }
+
+    /**
+     * Enable merges on the current thread.
+     */
+    void enableMerge() {
+        assert !enabled.get();
+        enabled.set(Boolean.TRUE);
+    }
+
+    /**
+     * Disable merges on the current thread.
+     */
+    void disableMerge() {
+        assert enabled.get();
+        enabled.set(Boolean.FALSE);
+    }
+
+    @Override
+    public void merge(IndexWriter writer) throws IOException {
+        if (enabled.get()) {
+            mergeScheduler.merge(writer);
+        }
+    }
+
+    @Override
+    public void close() throws IOException {
+        mergeScheduler.close();
+    }
+
+    @Override
+    public MergeScheduler clone() {
+        // Lucene IW makes a clone internally but since we hold on to this instance
+        // the clone will just be the identity.
+        return this;
+    }
+}

src/main/java/org/elasticsearch/index/merge/Merges.java

@@ -0,0 +1,107 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.merge;
+
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.index.MergeScheduler;
+
+import java.io.IOException;
+
+/**
+ * A helper to execute explicit merges of the {@link org.apache.lucene.index.IndexWriter} APIs. It
+ * holds additional logic which in case the merge scheduler is an {@link org.elasticsearch.index.merge.EnableMergeScheduler}
+ * then merges are explicitly enabled and disabled back at the end.
+ * <p/>
+ * In our codebase, at least until we can somehow use this logic in Lucene IW itself, we should only use
+ * this class to execute explicit merges. The explicit merge calls have been added to the forbidden APIs
+ * list to make sure we don't call them unless we use this class.
+ */
+public class Merges {
+
+    /**
+     * See {@link org.apache.lucene.index.IndexWriter#maybeMerge()}, with the additional
+     * logic of explicitly enabling merges if the scheduler is {@link org.elasticsearch.index.merge.EnableMergeScheduler}.
+     */
+    public static void maybeMerge(IndexWriter writer) throws IOException {
+        MergeScheduler mergeScheduler = writer.getConfig().getMergeScheduler();
+        if (mergeScheduler instanceof EnableMergeScheduler) {
+            ((EnableMergeScheduler) mergeScheduler).enableMerge();
+            try {
+                writer.maybeMerge();
+            } finally {
+                ((EnableMergeScheduler) mergeScheduler).disableMerge();
+            }
+        } else {
+            writer.maybeMerge();
+        }
+    }
+
+    /**
+     * See {@link org.apache.lucene.index.IndexWriter#forceMerge(int)}, with the additional
+     * logic of explicitly enabling merges if the scheduler is {@link org.elasticsearch.index.merge.EnableMergeScheduler}.
+     */
+    public static void forceMerge(IndexWriter writer, int maxNumSegments) throws IOException {
+        forceMerge(writer, maxNumSegments, true);
+    }
+
+    /**
+     * See {@link org.apache.lucene.index.IndexWriter#forceMerge(int, boolean)}, with the additional
+     * logic of explicitly enabling merges if the scheduler is {@link org.elasticsearch.index.merge.EnableMergeScheduler}.
+     */
+    public static void forceMerge(IndexWriter writer, int maxNumSegments, boolean doWait) throws IOException {
+        MergeScheduler mergeScheduler = writer.getConfig().getMergeScheduler();
+        if (mergeScheduler instanceof EnableMergeScheduler) {
+            ((EnableMergeScheduler) mergeScheduler).enableMerge();
+            try {
+                writer.forceMerge(maxNumSegments, doWait);
+            } finally {
+                ((EnableMergeScheduler) mergeScheduler).disableMerge();
+            }
+        } else {
+            writer.forceMerge(maxNumSegments, doWait);
+        }
+    }
+
+    /**
+     * See {@link org.apache.lucene.index.IndexWriter#forceMergeDeletes()}, with the additional
+     * logic of explicitly enabling merges if the scheduler is {@link org.elasticsearch.index.merge.EnableMergeScheduler}.
+     */
+    public static void forceMergeDeletes(IndexWriter writer) throws IOException {
+        forceMergeDeletes(writer, true);
+    }
+
+    /**
+     * See {@link org.apache.lucene.index.IndexWriter#forceMergeDeletes(boolean)}, with the additional
+     * logic of explicitly enabling merges if the scheduler is {@link org.elasticsearch.index.merge.EnableMergeScheduler}.
+     */
+    public static void forceMergeDeletes(IndexWriter writer, boolean doWait) throws IOException {
+        MergeScheduler mergeScheduler = writer.getConfig().getMergeScheduler();
+        if (mergeScheduler instanceof EnableMergeScheduler) {
+            ((EnableMergeScheduler) mergeScheduler).enableMerge();
+            try {
+                writer.forceMergeDeletes(doWait);
+            } finally {
+                ((EnableMergeScheduler) mergeScheduler).disableMerge();
+            }
+        } else {
+            writer.forceMergeDeletes(doWait);
+        }
+    }
+}

src/main/java/org/elasticsearch/index/merge/scheduler/ConcurrentMergeSchedulerProvider.java

@@ -59,7 +59,7 @@ public class ConcurrentMergeSchedulerProvider extends MergeSchedulerProvider {
     }
 
     @Override
-    public MergeScheduler newMergeScheduler() {
+    public MergeScheduler buildMergeScheduler() {
         CustomConcurrentMergeScheduler concurrentMergeScheduler = new CustomConcurrentMergeScheduler(logger, shardId, this);
         concurrentMergeScheduler.setMaxMergesAndThreads(maxMergeCount, maxThreadCount);
         schedulers.add(concurrentMergeScheduler);

src/main/java/org/elasticsearch/index/merge/scheduler/MergeSchedulerModule.java

@@ -22,16 +22,13 @@ package org.elasticsearch.index.merge.scheduler;
 import org.elasticsearch.common.inject.AbstractModule;
 import org.elasticsearch.common.settings.Settings;
 
-import static org.elasticsearch.index.merge.scheduler.MergeSchedulerModule.MergeSchedulerSettings.TYPE;
-
 /**
  *
  */
 public class MergeSchedulerModule extends AbstractModule {
 
-    public static class MergeSchedulerSettings {
-        public static final String TYPE = "index.merge.scheduler.type";
-    }
+    public static final String MERGE_SCHEDULER_TYPE_KEY = "index.merge.scheduler.type";
+    public static final Class<? extends MergeSchedulerProvider> DEFAULT = ConcurrentMergeSchedulerProvider.class;
 
     private final Settings settings;
 
@@ -42,7 +39,7 @@ public class MergeSchedulerModule extends AbstractModule {
     @Override
     protected void configure() {
         bind(MergeSchedulerProvider.class)
-                .to(settings.getAsClass(TYPE, ConcurrentMergeSchedulerProvider.class, "org.elasticsearch.index.merge.scheduler.", "MergeSchedulerProvider"))
+                .to(settings.getAsClass(MERGE_SCHEDULER_TYPE_KEY, DEFAULT, "org.elasticsearch.index.merge.scheduler.", "MergeSchedulerProvider"))
                 .asEagerSingleton();
     }
 }

src/main/java/org/elasticsearch/index/merge/scheduler/MergeSchedulerProvider.java

@@ -22,6 +22,7 @@ package org.elasticsearch.index.merge.scheduler;
 import org.apache.lucene.index.MergePolicy;
 import org.apache.lucene.index.MergeScheduler;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.merge.EnableMergeScheduler;
 import org.elasticsearch.index.merge.MergeStats;
 import org.elasticsearch.index.merge.OnGoingMerge;
 import org.elasticsearch.index.settings.IndexSettings;
@@ -36,7 +37,9 @@ import java.util.concurrent.CopyOnWriteArrayList;
 /**
  *
  */
-public abstract class MergeSchedulerProvider<T extends MergeScheduler> extends AbstractIndexShardComponent implements IndexShardComponent {
+public abstract class MergeSchedulerProvider extends AbstractIndexShardComponent implements IndexShardComponent {
+
+    public static final String FORCE_ASYNC_MERGE = "index.merge.force_async_merge";
 
     public static interface FailureListener {
         void onFailedMerge(MergePolicy.MergeException e);
@@ -110,7 +113,16 @@ public abstract class MergeSchedulerProvider<T extends MergeScheduler> extends A
         }
     }
 
-    public abstract T newMergeScheduler();
+    public final MergeScheduler newMergeScheduler() {
+        MergeScheduler scheduler = buildMergeScheduler();
+        // an internal settings, that would allow us to disable this behavior if really needed
+        if (indexSettings.getAsBoolean(FORCE_ASYNC_MERGE, true)) {
+            scheduler = new EnableMergeScheduler(scheduler);
+        }
+        return scheduler;
+    }
+
+    protected abstract MergeScheduler buildMergeScheduler();
 
     public abstract MergeStats stats();
 

src/main/java/org/elasticsearch/index/merge/scheduler/SerialMergeSchedulerProvider.java

@@ -48,7 +48,7 @@ public class SerialMergeSchedulerProvider extends MergeSchedulerProvider {
     }
 
     @Override
-    public MergeScheduler newMergeScheduler() {
+    public MergeScheduler buildMergeScheduler() {
         CustomSerialMergeScheduler scheduler = new CustomSerialMergeScheduler(logger, this);
         schedulers.add(scheduler);
         return scheduler;

src/test/java/org/elasticsearch/benchmark/fielddata/LongFieldDataBenchmark.java

@@ -37,6 +37,7 @@ import org.elasticsearch.index.fielddata.IndexNumericFieldData;
 import org.elasticsearch.index.mapper.ContentPath;
 import org.elasticsearch.index.mapper.Mapper.BuilderContext;
 import org.elasticsearch.index.mapper.core.LongFieldMapper;
+import org.elasticsearch.index.merge.Merges;
 import org.elasticsearch.indices.fielddata.breaker.DummyCircuitBreakerService;
 
 import java.util.Random;
@@ -51,6 +52,7 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return 1;
             }
+
             @Override
             public long nextValue() {
                 return RANDOM.nextInt(16);
@@ -60,6 +62,7 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return 1;
             }
+
             @Override
             public long nextValue() {
                 // somewhere in-between 2010 and 2012
@@ -70,6 +73,7 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return RANDOM.nextInt(3);
             }
+
             @Override
             public long nextValue() {
                 // somewhere in-between 2010 and 2012
@@ -80,6 +84,7 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return RANDOM.nextInt(3);
             }
+
             @Override
             public long nextValue() {
                 return 3 + RANDOM.nextInt(8);
@@ -89,6 +94,7 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return RANDOM.nextFloat() < 0.1f ? 1 : 0;
             }
+
             @Override
             public long nextValue() {
                 return RANDOM.nextLong();
@@ -98,6 +104,7 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return RANDOM.nextFloat() < 0.1f ? 1 + RANDOM.nextInt(5) : 0;
             }
+
             @Override
             public long nextValue() {
                 return RANDOM.nextLong();
@@ -107,12 +114,15 @@ public class LongFieldDataBenchmark {
             public int numValues() {
                 return 1 + RANDOM.nextInt(3);
             }
+
             @Override
             public long nextValue() {
                 return RANDOM.nextLong();
             }
         };
+
         public abstract int numValues();
+
         public abstract long nextValue();
     }
 
@@ -132,7 +142,7 @@ public class LongFieldDataBenchmark {
                 }
                 indexWriter.addDocument(doc);
             }
-            indexWriter.forceMerge(1);
+            Merges.forceMerge(indexWriter, 1);
             indexWriter.close();
 
             final DirectoryReader dr = DirectoryReader.open(dir);

src/test/java/org/elasticsearch/common/lucene/uid/VersionsTests.java

@@ -34,6 +34,7 @@ import org.elasticsearch.common.Numbers;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.index.mapper.internal.UidFieldMapper;
 import org.elasticsearch.index.mapper.internal.VersionFieldMapper;
+import org.elasticsearch.index.merge.Merges;
 import org.elasticsearch.index.merge.policy.IndexUpgraderMergePolicy;
 import org.elasticsearch.test.ElasticsearchLuceneTestCase;
 import org.hamcrest.MatcherAssert;
@@ -266,7 +267,7 @@ public class VersionsTests extends ElasticsearchLuceneTestCase {
                 .put("1", 0L).put("2", 0L).put("3", 0L).put("4", 4L).put("5", 5L).put("6", 6L).build();
 
         // Force merge and check versions
-        iw.forceMerge(1);
+        Merges.forceMerge(iw, 1);
         final AtomicReader ir = SlowCompositeReaderWrapper.wrap(DirectoryReader.open(iw.getDirectory()));
         final NumericDocValues versions = ir.getNumericDocValues(VersionFieldMapper.NAME);
         assertThat(versions, notNullValue());

src/test/java/org/elasticsearch/index/codec/postingformat/DefaultPostingsFormatTests.java

@@ -32,6 +32,7 @@ import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.index.codec.postingsformat.BloomFilterPostingsFormat;
 import org.elasticsearch.index.codec.postingsformat.Elasticsearch090PostingsFormat;
 import org.elasticsearch.index.mapper.internal.UidFieldMapper;
+import org.elasticsearch.index.merge.Merges;
 import org.elasticsearch.test.ElasticsearchTestCase;
 import org.junit.Test;
 
@@ -93,7 +94,7 @@ public class DefaultPostingsFormatTests extends ElasticsearchTestCase {
         for (int i = 0; i < 100; i++) {
             writer.addDocument(Arrays.asList(new TextField("foo", "foo bar foo bar", Store.YES), new TextField("some_other_field", "1234", Store.YES)));
         }
-        writer.forceMerge(1);
+        Merges.forceMerge(writer, 1);
         writer.commit();
         
         DirectoryReader reader = DirectoryReader.open(writer, false);

src/test/java/org/elasticsearch/index/engine/internal/InternalEngineTests.java

@@ -185,7 +185,7 @@ public class InternalEngineTests extends ElasticsearchTestCase {
         return new LogByteSizeMergePolicyProvider(store, new IndexSettingsService(new Index("test"), EMPTY_SETTINGS));
     }
 
-    protected MergeSchedulerProvider<?> createMergeScheduler() {
+    protected MergeSchedulerProvider createMergeScheduler() {
         return new SerialMergeSchedulerProvider(shardId, EMPTY_SETTINGS, threadPool);
     }
 
@@ -193,7 +193,7 @@ public class InternalEngineTests extends ElasticsearchTestCase {
         return createEngine(indexSettingsService, store, translog, createMergeScheduler());
     }
 
-    protected Engine createEngine(IndexSettingsService indexSettingsService, Store store, Translog translog, MergeSchedulerProvider<?> mergeSchedulerProvider) {
+    protected Engine createEngine(IndexSettingsService indexSettingsService, Store store, Translog translog, MergeSchedulerProvider mergeSchedulerProvider) {
         return new InternalEngine(shardId, defaultSettings, threadPool, indexSettingsService, new ShardIndexingService(shardId, EMPTY_SETTINGS, new ShardSlowLogIndexingService(shardId, EMPTY_SETTINGS, indexSettingsService)), null, store, createSnapshotDeletionPolicy(), translog, createMergePolicy(), mergeSchedulerProvider,
                 new AnalysisService(shardId.index()), new SimilarityService(shardId.index()), new CodecService(shardId.index()));
     }

src/test/java/org/elasticsearch/index/fielddata/FilterFieldDataTest.java

@@ -26,6 +26,7 @@ import org.elasticsearch.common.settings.ImmutableSettings;
 import org.elasticsearch.index.fielddata.AtomicFieldData.WithOrdinals;
 import org.elasticsearch.index.fielddata.ScriptDocValues.Strings;
 import org.elasticsearch.index.fielddata.ordinals.Ordinals.Docs;
+import org.elasticsearch.index.merge.Merges;
 import org.junit.Test;
 
 import java.util.Random;
@@ -60,7 +61,7 @@ public class FilterFieldDataTest extends AbstractFieldDataTests {
             }
             writer.addDocument(d);
         }
-        writer.forceMerge(1);
+        Merges.forceMerge(writer, 1);
         AtomicReaderContext context = refreshReader();
         String[] formats = new String[] { "fst", "paged_bytes"};
         
@@ -163,7 +164,7 @@ public class FilterFieldDataTest extends AbstractFieldDataTests {
             writer.addDocument(d);
         }
         System.out.println(hundred + " " + ten + " " + five);
-        writer.forceMerge(1);
+        Merges.forceMerge(writer, 1);
         AtomicReaderContext context = refreshReader();
         String[] formats = new String[] { "fst", "paged_bytes"};
         for (String format : formats) {

src/test/java/org/elasticsearch/index/fielddata/LongFieldDataTests.java

@@ -28,6 +28,7 @@ import org.apache.lucene.document.StringField;
 import org.apache.lucene.index.Term;
 import org.elasticsearch.common.settings.ImmutableSettings;
 import org.elasticsearch.index.fielddata.plain.PackedArrayAtomicFieldData;
+import org.elasticsearch.index.merge.Merges;
 import org.joda.time.DateTimeZone;
 import org.junit.Test;
 
@@ -325,7 +326,7 @@ public class LongFieldDataTests extends AbstractNumericFieldDataTests {
             }
             writer.addDocument(doc);
         }
-        writer.forceMerge(1);
+        Merges.forceMerge(writer, 1);
 
         final IndexNumericFieldData indexFieldData = getForField("value");
         final AtomicNumericFieldData atomicFieldData = indexFieldData.load(refreshReader());

src/test/java/org/elasticsearch/search/suggest/completion/CompletionPostingsFormatTest.java

@@ -41,6 +41,7 @@ import org.elasticsearch.index.codec.postingsformat.PreBuiltPostingsFormatProvid
 import org.elasticsearch.index.mapper.FieldMapper.Names;
 import org.elasticsearch.index.mapper.core.AbstractFieldMapper;
 import org.elasticsearch.index.mapper.core.CompletionFieldMapper;
+import org.elasticsearch.index.merge.Merges;
 import org.elasticsearch.search.suggest.SuggestUtils;
 import org.elasticsearch.search.suggest.completion.Completion090PostingsFormat.LookupFactory;
 import org.elasticsearch.test.ElasticsearchTestCase;
@@ -265,7 +266,7 @@ public class CompletionPostingsFormatTest extends ElasticsearchTestCase {
             writer.addDocument(doc);
         }
         writer.commit();
-        writer.forceMerge(1);
+        Merges.forceMerge(writer, 1);
         writer.commit();
         DirectoryReader reader = DirectoryReader.open(writer, true);
         assertThat(reader.leaves().size(), equalTo(1));

src/test/java/org/elasticsearch/test/ElasticsearchIntegrationTest.java

@@ -33,7 +33,6 @@ import org.elasticsearch.action.admin.cluster.health.ClusterHealthStatus;
 import org.elasticsearch.action.admin.cluster.node.stats.NodeStats;
 import org.elasticsearch.action.admin.cluster.node.stats.NodesStatsResponse;
 import org.elasticsearch.action.admin.cluster.state.ClusterStateResponse;
-import org.elasticsearch.action.admin.indices.cache.clear.ClearIndicesCacheResponse;
 import org.elasticsearch.action.admin.indices.create.CreateIndexRequestBuilder;
 import org.elasticsearch.action.admin.indices.exists.indices.IndicesExistsResponse;
 import org.elasticsearch.action.admin.indices.flush.FlushResponse;
@@ -61,6 +60,10 @@ import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.index.mapper.FieldMapper.Loading;
 import org.elasticsearch.index.merge.policy.*;
+import org.elasticsearch.index.merge.scheduler.ConcurrentMergeSchedulerProvider;
+import org.elasticsearch.index.merge.scheduler.MergeSchedulerModule;
+import org.elasticsearch.index.merge.scheduler.MergeSchedulerProvider;
+import org.elasticsearch.index.merge.scheduler.SerialMergeSchedulerProvider;
 import org.elasticsearch.indices.IndexMissingException;
 import org.elasticsearch.indices.IndexTemplateMissingException;
 import org.elasticsearch.repositories.RepositoryMissingException;
@@ -295,7 +298,7 @@ public abstract class ElasticsearchIntegrationTest extends ElasticsearchTestCase
             client().admin().indices().preparePutTemplate("random_index_template")
                     .setTemplate("*")
                     .setOrder(0)
-                    .setSettings(setRandomNormsLoading(setRandomMergePolicy(getRandom(), ImmutableSettings.builder())
+                    .setSettings(setRandomNormsLoading(setRandomMerge(getRandom(), ImmutableSettings.builder())
                             .put(INDEX_SEED_SETTING, randomLong())))
                     .execute().actionGet();
         }
@@ -308,24 +311,38 @@ public abstract class ElasticsearchIntegrationTest extends ElasticsearchTestCase
         return builder;
     }
 
-    private static ImmutableSettings.Builder setRandomMergePolicy(Random random, ImmutableSettings.Builder builder) {
+    private static ImmutableSettings.Builder setRandomMerge(Random random, ImmutableSettings.Builder builder) {
         if (random.nextBoolean()) {
             builder.put(AbstractMergePolicyProvider.INDEX_COMPOUND_FORMAT,
                     random.nextBoolean() ? random.nextDouble() : random.nextBoolean());
         }
-        Class<? extends MergePolicyProvider<?>> clazz = TieredMergePolicyProvider.class;
+        Class<? extends MergePolicyProvider<?>> mergePolicy = TieredMergePolicyProvider.class;
         switch (random.nextInt(5)) {
             case 4:
-                clazz = LogByteSizeMergePolicyProvider.class;
+                mergePolicy = LogByteSizeMergePolicyProvider.class;
                 break;
             case 3:
-                clazz = LogDocMergePolicyProvider.class;
+                mergePolicy = LogDocMergePolicyProvider.class;
                 break;
             case 0:
-                return builder; // don't set the setting at all
+                mergePolicy = null;
         }
-        assert clazz != null;
-        builder.put(MergePolicyModule.MERGE_POLICY_TYPE_KEY, clazz.getName());
+        if (mergePolicy != null) {
+            builder.put(MergePolicyModule.MERGE_POLICY_TYPE_KEY, mergePolicy.getName());
+        }
+
+        if (random.nextBoolean()) {
+            builder.put(MergeSchedulerProvider.FORCE_ASYNC_MERGE, random.nextBoolean());
+        }
+        switch (random.nextInt(5)) {
+            case 4:
+                builder.put(MergeSchedulerModule.MERGE_SCHEDULER_TYPE_KEY, SerialMergeSchedulerProvider.class.getName());
+                break;
+            case 3:
+                builder.put(MergeSchedulerModule.MERGE_SCHEDULER_TYPE_KEY, ConcurrentMergeSchedulerProvider.class.getName());
+                break;
+        }
+
         return builder;
     }