How to validate buildpack is having an effect

[ncri]

Just a quick question how to validate the buildpack is in effect. I tried what's suggested in some places:

ruby -r rbconfig -e "puts RbConfig::CONFIG['LIBS']"

But this only gives me:

-lpthread -lgmp -ldl -lcrypt -lm 

Although the buildpack seems to do something, as I saw a pthread error similar to the one in #3 and had to revert to version 5.0.1 as suggested to make it go away.

[gaffneyc]

There was a long discussion in mojodna/issues/6 but I don't believe anyone came up with a good answer.

The most correct answer would probably involve dropping into C to check if some the jemalloc functions were defined or the lib was loaded (this is beyond my depth).

A niece approach would be to check the LD_PRELOAD is being set (below). This won't work if the library doesn't exist (which was an issue before JEMALLOC_ENABLED was an option).

/jemalloc/.match?(ENV["LD_PRELOAD"])

[ncri]

Okay, thx!

[johnsudaar]

A good way i found on docker-library/ruby#182 (comment) is using:

MALLOC_CONF=stats_print:true ruby -e "exit"

If jemalloc is activated it will generate the jemalloc stats overwise it will just exit.