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https://issues.apache.org/jira/browse/HDDS-2199?focusedWorklogId=321795&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-321795
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ASF GitHub Bot logged work on HDDS-2199:
----------------------------------------
Author: ASF GitHub Bot
Created on: 02/Oct/19 10:19
Start Date: 02/Oct/19 10:19
Worklog Time Spent: 10m
Work Description: elek commented on 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_r330472747
##########
File path:
hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/server/SCMBlockProtocolServer.java
##########
@@ -295,7 +297,33 @@ public ScmInfo getScmInfo() throws IOException {
boolean auditSuccess = true;
try{
NodeManager nodeManager = scm.getScmNodeManager();
- Node client = nodeManager.getNodeByAddress(clientMachine);
Review comment:
I am trying to understand why is this big block is not just as simple:
```
Node client = null;
List<DatanodeDetails> possibleClients =
nodeManager.getNodesByAddress(clientMachine);
if (possibleClients.size()>0){
client = possibleClients.get(0);
}
```
It seems to be a logic to find a datanode which is on the same host as the
client. I am not sure if we need this tricky randomization (or choosing the
first possible datanodes): if client is null, we don't need sort (handled by
the sort method below), if there are multiple datanodes on the same client we
can choose the first one as in the topology sort it doesn't matter which one is
chosen.
But please fix me if I am wrong.
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Issue Time Tracking
-------------------
Worklog Id: (was: 321795)
Time Spent: 1h 40m (was: 1.5h)
> In SCMNodeManager dnsToUuidMap cannot track multiple DNs on the same host
> -------------------------------------------------------------------------
>
> Key: HDDS-2199
> URL: https://issues.apache.org/jira/browse/HDDS-2199
> Project: Hadoop Distributed Data Store
> Issue Type: Bug
> Affects Versions: 0.5.0
> Reporter: Stephen O'Donnell
> Assignee: Stephen O'Donnell
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> Often in test clusters and tests, we start multiple datanodes on the same
> host.
> In SCMNodeManager.register() there is a map of hostname -> datanode UUID
> called dnsToUuidMap.
> If several DNs register from the same host, the entry in the map will be
> overwritten and the last DN to register will 'win'.
> This means that the method getNodeByAddress() does not return the correct
> DatanodeDetails object when many hosts are registered from the same address.
> This method is only used in SCMBlockProtocolServer.sortDatanodes() to allow
> it to see if one of the nodes matches the client, but it need to be used by
> the Decommission code.
> Perhaps we could change the getNodeByAddress() method to returns a list of
> DNs? In normal production clusters, there should only be one returned, but in
> test clusters, there may be many. Any code looking for a specific DN entry
> would need to iterate the list and match on the port number too, as host:port
> would be the unique definition of a datanode.
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