Make DistributorDirectory not call fsync on sub directories and missing files.

Related to #9145

src/main/java/org/elasticsearch/index/store/DistributorDirectory.java

@@ -25,8 +25,11 @@ import org.elasticsearch.index.store.distributor.Distributor;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.IdentityHashMap;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 
 /**
@@ -102,8 +105,20 @@ public final class DistributorDirectory extends Directory {
     @Override
     public void sync(Collection<String> names) throws IOException {
         // no need to sync this operation it could be long running too
-        for (Directory dir : distributor.all()) {
+        final Map<Directory, Collection<String>> perDirectory = new IdentityHashMap<>();
-            dir.sync(names);
+        for (String name : names) {
+            final Directory dir = getDirectory(name);
+            Collection<String> dirNames = perDirectory.get(dir);
+            if (dirNames == null) {
+                dirNames = new ArrayList<>();
+                perDirectory.put(dir, dirNames);
+            }
+            dirNames.add(name);
+        }
+        for (Map.Entry<Directory, Collection<String>> entry : perDirectory.entrySet()) {
+            final Directory dir = entry.getKey();
+            final Collection<String> dirNames = entry.getValue();
+            dir.sync(dirNames);
         }
     }
 

src/test/java/org/elasticsearch/index/store/DistributorDirectoryTest.java

@@ -19,7 +19,10 @@
 package org.elasticsearch.index.store;
 
 import com.carrotsearch.randomizedtesting.annotations.*;
+import com.carrotsearch.randomizedtesting.generators.RandomInts;
 import com.carrotsearch.randomizedtesting.generators.RandomPicks;
+import com.google.common.collect.ImmutableSet;
+
 import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.store.*;
 import org.apache.lucene.util.IOUtils;
@@ -36,6 +39,9 @@ import java.io.IOException;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
 
 @ThreadLeakFilters(defaultFilters = true, filters = {ElasticsearchThreadFilter.class})
 @ThreadLeakScope(ThreadLeakScope.Scope.SUITE)
@@ -157,4 +163,41 @@ public class DistributorDirectoryTest extends BaseDirectoryTestCase {
             IOUtils.close(dd);
         }
     }
+
+    public void testSync() throws IOException {
+        final Set<String> syncedFiles = new HashSet<>();
+        final Directory[] directories = new Directory[RandomInts.randomIntBetween(random(), 1, 5)];
+        for (int i = 0; i < directories.length; ++i) {
+            final Directory dir = newDirectory();
+            directories[i] = new FilterDirectory(dir) {
+                @Override
+                public void sync(Collection<String> names) throws IOException {
+                    super.sync(names);
+                    syncedFiles.addAll(names);
+                }
+            };
+        }
+
+        final Directory directory = new DistributorDirectory(directories);
+
+        for (String file : Arrays.asList("a.bin", "b.bin")) {
+            try (IndexOutput out = directory.createOutput(file, IOContext.DEFAULT)) {
+                out.writeInt(random().nextInt());
+            }
+        }
+
+        // syncing on a missing file throws an exception
+        try {
+            directory.sync(Arrays.asList("a.bin", "c.bin"));
+        } catch (FileNotFoundException e) {
+            // expected
+        }
+        assertEquals(ImmutableSet.of(), syncedFiles);
+
+        // but syncing on existing files actually delegates
+        directory.sync(Arrays.asList("a.bin", "b.bin"));
+        assertEquals(ImmutableSet.of("a.bin", "b.bin"), syncedFiles);
+
+        directory.close();
+    }
 }