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https://issues.apache.org/jira/browse/CASSANDRA-3706?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13190272#comment-13190272
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Dave Brosius edited comment on CASSANDRA-3706 at 1/21/12 2:24 AM:
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Ah, the fact that system was local-only had escaped me, this makes your
original comments (brandon) make alot more sense to me.
As Jonathan points out, it makes no sense to save this information in the
system keyspace then, as the point of this storage is for easing disaster
recovery, and if the node goes down, the yaml as depicted in the keyspace is no
more likely to survive than the yaml file in the conf directory. If this
feature is to have value at all, it must be replicated, so a secondary
quasi-system keyspace that is replicated would be needed.
I planned to add support for the cassandra-env and log4j files as well, but
wanted to get feed back first before proceeding with those as those files are
not first class files in cassandra as the yaml file is, and thus marginally
more tricky. Glad I did :)
As for an IP being a poor choice for key, I agree it's sub-optimal, however it
was used to ensure uniqueness, and have some tie back to the original machine
(albeit not absolute). The only other choice I could think of is an added field
in the yaml file such as cluster-node-id that had to be set by the
administrator, but then we need to rely on the administrator to choose a unique
one which is far less likely. To enforce this uniqueness that id would need to
be added to the gossip protocol, and nodes need to be rejected with conflicting
unique ids. All of that seems like overkill. While IPs seem problematic, I
don't know how problematic they really are in practice. While these cluster
nodes use gossip for communication, I still would wonder whether the standard
deployment would use dhcp for these machines, as they still would need to be
administered remotely. Thus for static ips, the changing ip problem wouldn't be
one. But perhaps i'm talking out my ear.
Let me know what you want to do, and i'll be glad to go forward, or cancel
whatever is appropriate.
was (Author: dbros...@apache.org):
Ah, the fact that system was local-only had escaped me, this makes your
original comments (brandon) make alot more sense.
As Jonathan points out, it makes no sense to save this information in the
system keyspace then, as the point of this storage is for easing disaster
recovery, and if the node goes down, the yaml as depicted in the keyspace is no
more likely to survive than the yaml file in the conf directory. If this
feature is to have value at all, it must be replicated, so a secondary
quasi-system keyspace that is replicated would be needed.
I planned to add support for the cassandra-env and log4j files as well, but
wanted to get feed back first before proceeding with those as those files are
not first class files in cassandra as the yaml file is, and thus marginally
more tricky. Glad I did :)
Let me know what you want to do, and i'll be glad to go forward, or cancel
whatever is appropriate.
> Back up configuration files on startup
> --------------------------------------
>
> Key: CASSANDRA-3706
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3706
> Project: Cassandra
> Issue Type: New Feature
> Components: Tools
> Reporter: Jonathan Ellis
> Assignee: Dave Brosius
> Priority: Minor
> Labels: lhf
> Fix For: 1.1
>
> Attachments: save_configuration.diff, save_configuration_2.diff,
> save_configuration_3.diff
>
>
> Snapshot can backup user data, but it's also nice to be able to have
> known-good configurations saved as well in case of accidental snafus or even
> catastrophic loss of a cluster. If we check for changes to cassandra.yaml,
> cassandra-env.sh, and maybe log4j-server.properties on startup, we can back
> them up to a columnfamily that can then be handled by normal snapshot/backup
> procedures.
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