[HDFS-14279] [SBN Read] Race condition in ObserverReadProxyProvider

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Component/s: hdfs, namenode
• Target Version/s: 3.3.0
• Assignee: Erik Krogen Assign to me
• Reporter: Erik Krogen
• Created: 14/Feb/19 16:57
• Updated: 22/Feb/19 22:14
• Resolved: 22/Feb/19 22:00

Description

There is a race condition in ObserverReadProxyProvider#getCurrentProxy():

  private NNProxyInfo<T> getCurrentProxy() {
    if (currentProxy == null) {
      changeProxy(null);
    }
    return currentProxy;
  }

currentProxy is a volatile. Another changeProxy() could occur after the changeProxy() and before the return, thus making the return value incorrect. I have seen this result in an NPE.

Issue Links

• is related to: HDFS-12943 Consistent Reads from Standby Node