Redo, buildroot, and serializing parallel logs

Correct, both the technique described in that article and the feature that eventually wound up in GNU make only disentangle output from concurrently executing build processes. With significantly more work GNU make could probably be made to enforce a deterministic order.

However, Electric Make does emit the output in a deterministic order, in fact in exactly the same order as the build would have produced had it run serially. In practice the delayed output is not such a big deal -- people just don't really seem to care that much, when the build overall finishes 20x - 30x faster than it used to. Electric Make also generates an annotated build log, essentially an XML-marked-up version of the log, which contains a tremendous amount of additional information about the build and vastly simplifies debugging, actually.

A lot of devops tools, including Ansible and Salt, have higher-level concepts of ordering across hosts. In some cases this is implicit in the way the tool operates and people just take advantage of it, but in others (like Salt's orchestrate runner) the ordering of operations across hosts is explicitly defined by users. That can be useful for scripting blue/green deployment cutovers, pushing out new load balancer rules, etc.

> I'm actually curious about things like ansible; what exactly does it do that you couldn't just do with a bunch of redo scripts?

That might be more of a philosophical question :-) Most of those tools could be replaced with a sufficiently intelligent set of scripts. I think they get their popularity from providing more convenient syntax, building in parallelism for applying changes across hosts, offering cross-platform ways of doing common admin actions like creating accounts, etc.

But if you look at them the right way, they definitely share a lot in common with build systems, particularly when it comes to managing dependent actions.