How we upgraded a CFEngine cluster

blog-cfengine-logoThis post describes how we performed, on a cluster of ours, an upgrade of both the CFEngine policies, and of the CFEngine software itself from 3.3.5 to 3.4.4. The tools we used for the job were an editor and meld to edit the policies and merge changes from different branches, and cfengine itself (in particular cf-runagent), and clusterssh to apply the changes. I don’t claim this is a perfect procedure, and it wouldn’t scale to very big clusters; but in our case, the cluster was small enough to allow for some manual operations, and we took the opportunity to do things step by step, ensuring that nothing bad could happen to the production nodes at any time. On bigger clusters, with a better test environment, and with more “instrumentation” to monitor the changes, handwork could be reduced further, and the whole update would take less time. In our case, the bigger part was done between the workday start and the lunch break (about 3 hours). Continue reading