[HDDS-1843] Undetectable corruption after restart of a datanode

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 0.5.0
• Fix Version/s: 0.5.0
• Component/s: Ozone Datanode
• Labels: pull-request-available
• Target Version/s: 0.5.0
• Assignee: Shashikant Banerjee
• Reporter: Shashikant Banerjee
• Created: 22/Jul/19 15:20
• Updated: 24/Feb/20 20:54
• Resolved: 09/Sep/19 17:16

Description

Right now, all write chunks use BufferedIO ie, sync flag is disabled by default. Also, Rocks Db metadata updates are done in Rocks DB cache first at Datanode. In case, there comes a situation where the buffered chunk data as well as the corresponding metadata update is lost as a part of datanode restart, it may lead to a situation where, it will not be possible to detect the corruption (not even with container scanner) of this nature in a reasonable time frame, until and unless there is a client IO failure or Recon server detects it over time. In order to atleast to detect the problem, Ratis snapshot on datanode should sync the rocks db file . In such a way, ContainerScanner will be able to detect this.We can also add a metric around sync to measure how much of a throughput loss it can incurr.

Thanks msingh for suggesting this.

Issue Links

• links to: GitHub Pull Request #1364