backup bouncer test suite

[jtk]

Originally Posted by dnanian

We're aware of the fifos and devices not passing. It's something we'll look at in the future, but they -- unlike the other items -- tend not to be the kinds of things you'd want to copy.

That's true for devices, but FIFOs should be recreated or ignored (and the fact that it was ignored logged) otherwise things that depend on the FIFO's behavior tend to break in very strange and hard to diagnose ways.

[FIFOs] don't really have "meaning" across an execution (they don't even have any contents), so we decided not to handle them (they're kind of like VM swap files and temporary files, to our mind).

That's not strictly true. FIFOs are often used to allow asynchronous communication between processes and often should be retained between executions. In fact, they're usually only created when persistence is desired -- otherwise there are other, more efficient, mechanisms available.

Here's a (real) example:

Say I want to know what a system process is doing by reading its log and performing some action based on that. I can configure syslog to record that daemon's process to a FIFO in addition to the standard log files, then point my process at the fifo and parse the byte stream as I get it, allowing me to do what I need to do without hacking the daemon or executing my process in a privileged mode. Since I want my process to run at startup and I don't really have much control of when it starts relative to the syslogd or the daemon process I'm watching, the FIFO needs to be persistent. Otherwise syslogd will create it as a standard file and my process will be SOL when it tries to open it.

Very useful.

Oh, and put my vote in the "I'd really like to see FIFOs copied correctly" bin. Thanks!