[jira] [Commented] (CASSANDRA-19394) Rethink dumping of cluster metadata via CMSOperationsMBean

["Marcus Eriksson (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-19394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17817404#comment-17817404 ] 

Marcus Eriksson commented on CASSANDRA-19394:
---------------------------------------------

This is used for emergencies - you dump a metadata, modify it and then boot an instance with it - it requires local access to the machine to be able to start with the modified cluster metadata.

Don't think we should change this.

We should at some point add a way to dump the cluster metadata in a human readable format though

> Rethink dumping of cluster metadata via CMSOperationsMBean
> ----------------------------------------------------------
>
>                 Key: CASSANDRA-19394
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-19394
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Tool/nodetool, Transactional Cluster Metadata
>            Reporter: Stefan Miklosovic
>            Priority: Normal
>
> I think there are two problems in the implementation of dumping ClusterMetadata in CMSOperationsMBean
> 1) A dump is saved in a file and dumpClusterMetadata methods will return just a file name where that dump is. However, nodetool / JMX call to MBean (or any place this method is invoked from, we would like to offer a command in nodetool which returns the dump) is meant to be used from anywhere, remotely, so what happens when we execute nodetool or call these methods on a machine different from a machine a node runs on? E.g. admins can just have some jumpbox to a cluster they manage, they do not necessarily have access to nodes themselves. So they would not be able to read it.
> 2) It creates temp file which is not deleted so /tmp will be populated with these dumps until node is turned off which might take a lot of time and can consume a lot of disk space if dumps are done frequently and they are big. An adversary might just dump cluster metadata until no disk space is left.
> What I propose is that we would return all dump string, not just a filename where we save it. We can also format the output on the client or we can tell server what format we want the dump to be returned in. 
> If there is a concern about size of data to be returned, we might optionally allow dumps to be returned as compressed by simple zipping on server and unzipping on client where "zipper" is a standard java.util.zip so it basically doesn't matter what jvm runs on client and server.



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