Head chunk pr under feature flag

[Julien Pivotto]

Dear developers,

Do you think we could hide the head chunk PR under a feature flag for
now?

I observe that to run some of the test it creates in my tmpfs
directories of 16GB, then tests just fail.

As far as I know Prometheus should only require Posix compliant file
systems and to the best of my knowledge, tmpfs is Posix compliant.

$ go test -run TestSubquerySelector -v
=== RUN TestSubquerySelector
TestSubquerySelector: test.go:536: closing test storage: sync
/tmp/test_storage431942557/chunks_head/000028: file already closed
--- FAIL: TestSubquerySelector (1.23s)
FAIL
exit status 1
FAIL github.com/prometheus/prometheus/promql 1.237s

Chaning TMPDIR to ext4 make the test work again.

$ du -hs
/tmp/test_storage431942557/*
14G /tmp/test_storage431942557/chunks_head
0 /tmp/test_storage431942557/lock
128K /tmp/test_storage431942557/wal

I think that overall that change might have many other blind spots, so I
am wondering if that would be possible to somehow hide it under a
feature flag, disabled by default?


--
Julien Pivotto
@roidelapluie

[Brian Brazil]

If we've this sort of issue I think we should be looking to fix that prior to release, rather than putting out buggy code.

--

Brian Brazil

www.robustperception.io