[Mailman-Users] Mailman redundancy setup
david.westlund at axis.com
Thu Oct 25 14:50:31 CEST 2012
I am investigating doing a redundant setup of a mailman installation. We do not care about load balancing, only fail over. I have read through all I can found about this, including the following article on the FAQ:
I am planning to solve this by having an ordinary passive - active with a shared ip number between the hosts. My idea is to have mailman installations on both servers, but point out an NFS area for storing the data that needs to be available on all nodes in the setup.
The big difference between failover and load balancing (described in the FAQ post that I linked to) is of course that whenever there is a fail over, there is a good chance that the other mailman instance exited abruptly, leaving lock files and temporary data. This makes an argument for storing lock files locally. On the other hand, we do not want a situation where data gets corrupted even if both hosts end up running simultaneously. I have some questions, perhaps someone here has an answer:
* If we store lock files on an NFS area and one node goes down without removing any locks, will the other node be able to start mailman?
* According to http://wiki.list.org/pages/viewpage.action?pageId=4030621, qrunner does not use locks. However, I see a file named "master-qrunner" in the locks directory. Suppose that our master node went down without removing any lock files, would the master-qrunner file cause the qrunner on the other node to not start?
* On the page http://wiki.list.org/pages/viewpage.action?pageId=4030621 they mention that "If you set up /usr/local/mailman/qfiles to be shared across NFS and don't set up dedicated slices for each group of queue runners, you will be SERIOUSLY SCREWED." In what way?
* Say that we store locks locally, store data on an NFS node and accidentally start two instances of mailman on two different machines. Do we risk data corruption, or is the worst thing that can happen that changes are overwritten?
* Is there some documentation that I have not found about how locks are used in Mailman?
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