sodonnel commented on a change in pull request #1551: HDDS-2199 In
SCMNodeManager dnsToUuidMap cannot track multiple DNs on the same host
URL: https://github.com/apache/hadoop/pull/1551#discussion_r331163439
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File path:
hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/server/SCMBlockProtocolServer.java
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@@ -295,7 +297,33 @@ public ScmInfo getScmInfo() throws IOException {
boolean auditSuccess = true;
try{
NodeManager nodeManager = scm.getScmNodeManager();
- Node client = nodeManager.getNodeByAddress(clientMachine);
Review comment:
Reflecting on this issue some more, I think the simplified logic you have
suggested is better and the problem is better solved in getDistanceByCost -
rather than comparing just the node objects are the same, we should test if
they are the same hostname and if so treat that as a zero distance match too.
Unfortunately, as that method takes Node objects rather than
DatanodeDetails, this is not trivial to do.
The code path under question here is only relevant for clusters with more
than one datanode on the same host, and by definition that is a non-production
setup. The only consequence of the change you have suggested over my original
code, is that the client may get the wrong 'cost to reach a datanode' sometimes
on test clusters - nothing will fail, so the impact of this issue is very low.
Therefore if you are happy, I think we should commit the latest version
(which has your simplified logic) and create a followup Jira to look into
fixing getDistanceByCost somehow.
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