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https://issues.apache.org/jira/browse/CASSANDRA-5171?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis updated CASSANDRA-5171:
--------------------------------------
Priority: Critical (was: Trivial)
Affects Version/s: (was: 1.2.0)
0.7.1
Fix Version/s: (was: 1.2.1)
1.2.6
Issue Type: Bug (was: Improvement)
Summary: Save EC2Snitch topology information in system table
(was: Enhance Ec2Snitch gossip info.)
This was reverted in CASSANDRA-5432, but I think the problem it solves is
actually pretty severe, so I'm reopening it.
The problem is that pretty much everything from TokenMetadata to
NetworkTopologyStrategy assumes that once we see a node, the snitch can tell us
where it lives, and in particular that once the snitch tells us where a node
lives it won't change its answer.
So this is problematic:
{code}
public String getDatacenter(InetAddress endpoint)
{
if (endpoint.equals(FBUtilities.getBroadcastAddress()))
return ec2region;
EndpointState state =
Gossiper.instance.getEndpointStateForEndpoint(endpoint);
if (state == null || state.getApplicationState(ApplicationState.DC) ==
null)
return DEFAULT_DC;
return state.getApplicationState(ApplicationState.DC).value;
}
{code}
That is, if we don't know where a node belongs (e.g., we just restarted and
haven't been gosipped to yet), assume it's in {{DEFAULT_DC}}.
This can lead to data loss. Consider node X in DC1, where keyspace KS is
replicated. Suddenly X is yanked out of DC1 and placed in DC2, where KS is not
replicated. Nobody will bother querying X for the data in KS that was formerly
replicated to it. Even repair will not see it.
> Save EC2Snitch topology information in system table
> ---------------------------------------------------
>
> Key: CASSANDRA-5171
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5171
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.7.1
> Environment: EC2
> Reporter: Vijay
> Assignee: Vijay
> Priority: Critical
> Fix For: 1.2.6
>
> Attachments: 0001-CASSANDRA-5171.patch
>
>
> EC2Snitch currently waits for the Gossip information to understand the
> cluster information every time we restart. It will be nice to use already
> available system table info similar to GPFS.
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