Cache modification time of translog writer file

docs/changelog/95107.yaml

@@ -0,0 +1,5 @@
+pr: 95107
+summary: Cache modification time of translog writer file
+area: Engine
+type: enhancement
+issues: []

server/src/main/java/org/elasticsearch/index/translog/TranslogWriter.java

@@ -84,6 +84,12 @@ public class TranslogWriter extends BaseTranslogReader implements Closeable {
 
  private final DiskIoBufferPool diskIoBufferPool;
 
+ // package private for testing
+ LastModifiedTimeCache lastModifiedTimeCache;
+
+ // package private for testing
+ record LastModifiedTimeCache(long lastModifiedTime, long totalOffset, long syncedOffset) {}
+
  private TranslogWriter(
  final ShardId shardId,
  final Checkpoint initialCheckpoint,
@@ -127,6 +133,7 @@ private TranslogWriter(
  this.seenSequenceNumbers = Assertions.ENABLED ? new HashMap<>() : null;
  this.tragedy = tragedy;
  this.operationListener = operationListener;
+ this.lastModifiedTimeCache = new LastModifiedTimeCache(-1, -1, -1);
  }
 
  public static TranslogWriter create(
@@ -642,4 +649,13 @@ public final void close() throws IOException {
  protected final boolean isClosed() {
  return closed.get();
  }
+
+ @Override
+ public long getLastModifiedTime() throws IOException {
+ if (lastModifiedTimeCache.totalOffset() != totalOffset || lastModifiedTimeCache.syncedOffset() != lastSyncedCheckpoint.offset) {
+ long mtime = super.getLastModifiedTime();
+ lastModifiedTimeCache = new LastModifiedTimeCache(mtime, totalOffset, lastSyncedCheckpoint.offset);
+ }
+ return lastModifiedTimeCache.lastModifiedTime();
+ }
 }

server/src/test/java/org/elasticsearch/index/translog/TranslogTests.java

@@ -1586,6 +1586,40 @@ ChannelFactory getChannelFactory() {
  }
  }
 
+ public void testTranslogWriterLastModifiedTime() throws IOException {
+ Path tempDir = createTempDir();
+ try (Translog translog = create(tempDir)) {
+ long mtime = translog.getCurrent().getLastModifiedTime();
+ TranslogWriter.LastModifiedTimeCache mtimeCache = translog.getCurrent().lastModifiedTimeCache;
+ // no ops
+ long lastMtime = translog.getCurrent().getLastModifiedTime();
+ TranslogWriter.LastModifiedTimeCache lastMtimeCache = translog.getCurrent().lastModifiedTimeCache;
+ assertThat(lastMtime, equalTo(mtime));
+ assertEquals(lastMtimeCache, mtimeCache);
+
+ mtime = lastMtime;
+ mtimeCache = lastMtimeCache;
+ // add ops
+ int count = randomIntBetween(1, 100);
+ for (int i = 0; i < count; i++) {
+ translog.add(indexOp(randomAlphaOfLength(128), i, primaryTerm.get()));
+ }
+ lastMtime = translog.getCurrent().getLastModifiedTime();
+ lastMtimeCache = translog.getCurrent().lastModifiedTimeCache;
+ assertThat(lastMtime, greaterThanOrEqualTo(mtime));
+ assertThat(lastMtimeCache.totalOffset(), greaterThan(mtimeCache.totalOffset()));
+
+ mtime = lastMtime;
+ mtimeCache = lastMtimeCache;
+ // sync ops
+ translog.sync();
+ lastMtime = translog.getCurrent().getLastModifiedTime();
+ lastMtimeCache = translog.getCurrent().lastModifiedTimeCache;
+ assertThat(lastMtime, greaterThanOrEqualTo(mtime));
+ assertThat(lastMtimeCache.syncedOffset(), greaterThan(mtimeCache.syncedOffset()));
+ }
+ }
+
  public void testTranslogOperationListener() throws IOException {
  Path tempDir = createTempDir();
  final Settings settings = Settings.builder().put(IndexMetadata.SETTING_VERSION_CREATED, org.elasticsearch.Version.CURRENT).build();