arp7 commented on a change in pull request #949: HDDS-1672. Improve locking in
OzoneManager.
URL: https://github.com/apache/hadoop/pull/949#discussion_r295930273
##########
File path:
hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/OzoneManagerLock.java
##########
@@ -154,79 +178,137 @@ public void releaseVolumeLock(String volume) {
}
/**
- * Acquires S3 Bucket lock on the given resource.
+ * Acquires bucket lock on the given resource.
*
* <p>If the lock is not available then the current thread becomes
- * disabled for thread scheduling purposes and lies dormant until the lock
has
- * been acquired.
+ * disabled for thread scheduling purposes and lies dormant until the
+ * lock has been acquired.
*
- * @param s3BucketName S3Bucket Name on which the lock has to be acquired
+ * @param bucket Bucket on which the lock has to be acquired
*/
- public void acquireS3Lock(String s3BucketName) {
- // Calling thread should not hold any bucket lock.
- // You can take an Volume while holding S3 bucket lock, since
- // semantically an S3 bucket maps to the ozone volume. So we check here
- // only if ozone bucket lock is taken.
- if (hasAnyBucketLock()) {
+ public void acquireBucketLock(String volume, String bucket) {
+ if (hasAnyUserLock()) {
throw new RuntimeException(
"Thread '" + Thread.currentThread().getName() +
- "' cannot acquire S3 bucket lock while holding Ozone bucket " +
- "lock(s).");
+ "' cannot acquire bucket lock while holding User lock.");
}
- manager.lock(OM_S3_PREFIX + s3BucketName);
- myLocks.get().get(S3_BUCKET_LOCK).incrementAndGet();
+ manager.lock(OM_KEY_PREFIX + volume + OM_KEY_PREFIX + bucket);
+ myLocks.get().get(BUCKET_LOCK).incrementAndGet();
}
/**
- * Releases the volume lock on given resource.
+ * Releases the bucket lock on given resource.
*/
- public void releaseS3Lock(String s3BucketName) {
- manager.unlock(OM_S3_PREFIX + s3BucketName);
- myLocks.get().get(S3_BUCKET_LOCK).decrementAndGet();
+ public void releaseBucketLock(String volume, String bucket) {
+ manager.unlock(OM_KEY_PREFIX + volume + OM_KEY_PREFIX + bucket);
+ myLocks.get().get(BUCKET_LOCK).decrementAndGet();
}
/**
- * Acquires bucket lock on the given resource.
+ * Acquires user lock on the given resource.
*
* <p>If the lock is not available then the current thread becomes
* disabled for thread scheduling purposes and lies dormant until the
* lock has been acquired.
*
- * @param bucket Bucket on which the lock has to be acquired
+ * @param user User on which the lock has to be acquired
*/
- public void acquireBucketLock(String volume, String bucket) {
- manager.lock(OM_KEY_PREFIX + volume + OM_KEY_PREFIX + bucket);
- myLocks.get().get(BUCKET_LOCK).incrementAndGet();
+ public void acquireUserLock(String user) {
+ // In order to not maintain username's on which we have acquired lock,
+ // just checking have we acquired userLock before. If user want's to
+ // acquire user lock on multiple user's they should use
+ // acquireMultiUserLock. This is just a protection logic, to let not users
+ // use this if acquiring lock on multiple users. As currently, we have only
+ // use case we have for this is during setOwner operation in VolumeManager.
+ if (hasAnyUserLock()) {
+ LOG.error("Already have userLock");
+ throw new RuntimeException("For acquiring lock on multiple users, use " +
+ "acquireMultiLock method");
+ }
+ manager.lock(OM_USER_PREFIX + user);
+ myLocks.get().get(USER_LOCK).incrementAndGet();
}
/**
- * Releases the bucket lock on given resource.
+ * Releases the user lock on given resource.
*/
- public void releaseBucketLock(String volume, String bucket) {
- manager.unlock(OM_KEY_PREFIX + volume + OM_KEY_PREFIX + bucket);
- myLocks.get().get(BUCKET_LOCK).decrementAndGet();
+ public void releaseUserLock(String user) {
+ manager.unlock(OM_USER_PREFIX + user);
+ myLocks.get().get(USER_LOCK).decrementAndGet();
}
/**
- * Returns true if the current thread holds any volume lock.
- * @return true if current thread holds volume lock, else false
+ * Acquire user lock on 2 users. In this case, we compare 2 strings
+ * lexicographically, and acquire the locks according to the sorted order of
+ * the user names. In this way, when acquiring locks on multiple user's, we
+ * can avoid dead locks. This method should be called when single thread is
+ * acquiring lock on 2 users at a time.
+ *
+ * Example:
+ * ozone, hdfs -> lock acquire order will be hdfs, ozone
+ * hdfs, ozone -> lock acquire order will be hdfs, ozone
+ *
+ * @param newUser
+ * @param oldUser
*/
- private boolean hasAnyVolumeLock() {
- return myLocks.get().get(VOLUME_LOCK).get() != 0;
+ public void acquireMultiUserLock(String newUser, String oldUser) {
+ Preconditions.checkNotNull(newUser);
+ Preconditions.checkNotNull(oldUser);
+ int compare = newUser.compareTo(oldUser);
+
+ if (compare < 0) {
+ manager.lock(OM_USER_PREFIX + newUser);
+ manager.lock(OM_USER_PREFIX + oldUser);
Review comment:
If the second lock call fails then we should release the first lock before
returning.
The method should either get both locks or none.
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