default java.io.tmp location is too long

I have an issue with files created at temp directory having too long pathname. Please kindly see this SO question.

I managed to solve that by explicitly adding to my test target

"jvm_flags" = ["-Djava.io.tmpdir=/tmp"],

But that hurts the hermetical principle of testing. I suggest we offer much shorter yet unique tmp location for tests (somehting like /tmp/bazel-<unique-7-chars>)

WDYT?

[laszlocsomor]

FYI, I decided to roll back the --local_tmp_root flag, see: https://github.com/bazelbuild/bazel/issues/4621#issuecomment-366217321

For the record, there’s already a --test_tmpdir flag, which allows going down to a 42-character-long temp root, see https://github.com/bazelbuild/bazel/issues/4621#issuecomment-366217799

I’ll discuss with the team how to go forward.

[jmmv]

I generally agree with the sentiment that Bazel should be using TMPDIR-compliant paths. Unfortunately, Bazel as currently implemented, loves long paths. Addressing this specific issue here would add inconsistency, and it doesn’t seem trivial in this context. I also suspect several things would break given the current model in Bazel.

We have encountered this too in some tests and have fixed it by making any such affected test use /tmp directly, and then using mkdtemp or mkstemp to create directories or files safely within that. /tmp is open for writes from the sandbox, so this works.

Also, given that Unix domain socket names are restricted in length, any test that wants to create them must ensure that they fit within those limits. Relying on any environment variable or the cwd configured by Bazel to be “short enough” is bound to fail in some cases, so I’d say that we shouldn’t get into that business and that any tests relying on this specific limit must explicitly account for it.