runzhiwang commented on a change in pull request #709: HDDS-3244. Improve write
efficiency by opening RocksDB only once
URL: https://github.com/apache/hadoop-ozone/pull/709#discussion_r397568527
##########
File path:
hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/keyvalue/helpers/KeyValueContainerUtil.java
##########
@@ -73,14 +71,6 @@ public static void createContainerMetaData(File
containerMetaDataPath, File
throw new IOException("Unable to create directory for metadata storage."
+
" Path: " + containerMetaDataPath);
}
- MetadataStore store = MetadataStoreBuilder.newBuilder().setConf(conf)
- .setCreateIfMissing(true).setDbFile(dbFile).build();
Review comment:
@bshashikant @mukul1987
1. From the code, the [future
thread](https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java#L672)
do `getCachedStateMachineData ` in `readStateMachineData `and the [future
thread](https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java#L459)
do `createContainer` in `writeStateMachineData `are the same
[thread](https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java#L505).
Because `writeStateMachineData `called before `readStateMachineData`. So
leader must wait `createContainer `finish then `getCachedStateMachineData `and
append logs to the follower, so leader and follower are not independent,
follower must wait leader finish `createContainer`.
**How to improve it:**
I think this order can be improved by distinguishing the thread used by
`getCachedStateMachineData ` and `createContainer `, and if
[stateMachineDataCache.get(logIndex)](https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java#L617)
does not return null, leader can get stateMachineData from cache and need not
wait createContainer finish, thus leader and follower can be independent. But
if it return null, leader must finish createContaer than apennd logs to the
follower. So I think [data = readStateMachineData(requestProto, term,
logIndex)](https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java#L619)
should use the same thread with `createContainer` rather than the whole
[getCachedStateMachineData](https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java#L614).
What do you think ?
2. From the jaeger UI, you can also see follower create container after
leader finishing it.
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