[ROCKETMQ-195] concurrency bug when send data to slave.

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Duplicate
• Affects Version/s: 4.0.0-incubating
• Component/s: rocketmq-store
• Flags: Important
• Assignee: Xinyu Zhou
• Reporter: wenqi.huang
• Created: 10/May/17 01:43
• Updated: 10/May/17 11:52
• Resolved: 10/May/17 11:52

Description

when I test it，I found this error：

2017-05-09 18:38:55 ERROR SendMessageThread_4 - do sync transfer other node, wait return, but failed, topic: BenchmarkTest tags: null client address: 10.24.19.87
2017-05-09 18:38:55 WARN SendMessageThread_4 - putMessage not in lock eclipse time(ms)=1000, bodyLength=130
2017-05-09 18:38:55 WARN GroupTransferService - GroupTransferService service has exception.
java.lang.NullPointerException: null
at org.apache.rocketmq.store.ha.HAService$GroupTransferService.doWaitTransfer(HAService.java:278) ~[rocketmq-store-4.1.0-incubating-SNAPSHOT.jar:4.1.0-incubating-SNAPSHOT]
at org.apache.rocketmq.store.ha.HAService$GroupTransferService.run(HAService.java:301) ~[rocketmq-store-4.1.0-incubating-SNAPSHOT.jar:4.1.0-incubating-SNAPSHOT]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]

And I watch into this code and found that there is some concurrency bug,
then I try to fix it. pull request is:
https://github.com/apache/incubator-rocketmq/pull/102

as the code shows, the class pointer is volatile does not means ArrayList itself is threadsafe, so we need more job to ensure threadsafe.
(this pull request also fix some other bugs, the concurrency bug may cause NullPointerException or ConcurrentModificationException.)