(feat) Set segment file to be read-only after write and sync (#409)

* (feat) Set segment file to be read-only after write and sync

* (feat) use CopyOnWriteArrayList for hooks

jraft-core/src/main/java/com/alipay/sofa/jraft/storage/impl/RocksDBLogStorage.java

@@ -105,6 +105,13 @@ default void startJob() {
  default void finishJob() {
  }
 
+ /**
+ * Adds a callback that will be invoked after all sub jobs finish.
+ */
+ default void addFinishHook(final Runnable r) {
+
+ }
+
  /**
  * Set an exception to context.
  * @param e

jraft-core/src/main/java/com/alipay/sofa/jraft/storage/log/RocksDBSegmentLogStorage.java

@@ -24,6 +24,7 @@
 import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -83,14 +84,23 @@ public AllocatedResult(final IOException ie) {
  }
 
  public static class BarrierWriteContext implements WriteContext {
- private final CountDownEvent events = new CountDownEvent();
- private volatile Exception e;
+ private final CountDownEvent events = new CountDownEvent();
+ private volatile Exception e;
+ private volatile List<Runnable> hooks;
 
  @Override
  public void startJob() {
  this.events.incrementAndGet();
  }
 
+ @Override
+ public synchronized void addFinishHook(final Runnable r) {
+ if (this.hooks == null) {
+ this.hooks = new CopyOnWriteArrayList<>();
+ }
+ this.hooks.add(r);
+ }
+
  @Override
  public void finishJob() {
  this.events.countDown();
@@ -104,6 +114,11 @@ public void setError(final Exception e) {
  @Override
  public void joinAll() throws InterruptedException, IOException {
  this.events.await();
+ if (this.hooks != null) {
+ for (Runnable r : this.hooks) {
+ r.run();
+ }
+ }
  if (this.e != null) {
  throw new IOException("Fail to apppend entries", this.e);
  }
@@ -358,10 +373,11 @@ private SegmentFile createNewSegmentFile(final long logIndex, final int oldSegme
  final SegmentFile currLastFile = this.segments.get(this.segments.size() - 1);
  currLastFile.setLastLogIndex(logIndex - 1);
  ctx.startJob();
+ // Attach a finish hook to set last segment file to be read-only.
+ ctx.addFinishHook(() -> currLastFile.setReadOnly(true));
  // Run sync in parallel
  this.writeExecutor.execute(() -> {
  try {
- currLastFile.setReadOnly(true);
  currLastFile.sync(isSync());
  } catch (final IOException e) {
  ctx.setError(e);