Version checking for features can be dangerous because a commands output or availability may change in the future and now your charm also needs a "max-version", or "version-range" etc. A more robust solution could be something along the lines of a "feature-supported" query which would return whether that command is indeed supported in the active environment with the necessary syntax.
In JS this is a common workflow when dealing with cross browser compatibility issues and this issue is similar. The use could be something like... IS_LEADER_SUPPORTED=`juju supported-command is_leader` if [ "$IS_LEADER_SUPPORTED" == "true" ]; then # Do stuff else juju-log "Requires is_leader Juju command" fi -Jeff On Mon, Aug 10, 2015 at 2:32 PM, Matt Bruzek <[email protected]> wrote: > > We wrote a charm that needed election logic, so we used the new Juju > feature "is_leader". A user was interested in using a bundle that > contained this charm and it failed on them. It was hard to track down the > cause of the problem. It appears they were using an earlier version of > Juju that is available from universe and only the PPA had the more current > version. > > Read more about the problem here: > https://bugs.launchpad.net/charms/+source/etcd/+bug/1483380 > > I heard the "min-version" feature discussed at previous Cloud sprints but > to my knowledge we do not have it implemented yet. The idea was a charm > could specify in metadata.yaml what min-version of Juju they support. > > There are a lot of new features that juju-core are cranking out (and that > is *awesome*)! We have already run into this problem with a real user, and > will have the problem in the future. > > Can we reopen the discussion of min-version? Or some other method of > preventing this kind of problem in the future? > > - Matt Bruzek <[email protected]> > > -- > Juju-dev mailing list > [email protected] > Modify settings or unsubscribe at: > https://lists.ubuntu.com/mailman/listinfo/juju-dev > >
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