make config names unique

[evanmcc]

when using RELX_REPLACE_OS_VARS to start multiple release nodes, there
is a startup race since all of the releases are attempting to use the
same release file ($name.2.config). This code generates a random
identifier so that each release start uses a separate file, then cleans
up after itself so it doesn't leak config files.

I'm not super pleased by the rm at line 100. I think that it's safe enough, but ugly and potentially fragile. Any other suggestions are welcomed. I did it that way because it's rather hard to clean up since there are so many paths, and several of them end in exec. I wonder if this entire code path shouldn't additionally be walled off behind a MULTINODE_TESTING flag, since this isn't ideal behavior in production.

[tsloughter]

Been meaning to merge this. Kind of agree about the rm thing but also not as happy with having to set MULTINODE_TESTING...

[evanmcc]

could just change the config dir to /tmp/relx/ or something if you're replacing variables.

[saleyn]

Perhaps the generated vm.2.args and sys.2.config could just be saved to vm.${NAME}.args and sys.${NAME}.config and this wouldn't require that randomness and removal business?

[evanmcc]

that would better limit the number of files, I'll give it a shot.

[saleyn]

Actually @tsloughter just merged my PR, that affected some of this logic. Let me do another commit/PR that addresses this as I have a pretty clear idea of how to evaluate NAME properly, so that it's available before vm.*.args is generated.

[saleyn]

See this: #427

[evanmcc]

closing in favor of #427