metrics

gistfile1.txt

$ cat metrics.nix
with (import <nixpkgs> {});

runCommand "test-metrics" {} ''
performance-metrics() {
  thingname=$1
  shift
  if [ -n "${enablePhaseMetrics:-}" ]; then
    TIMEFORMAT="time.$thingname.user %U
time.$thingname.system %S
time.$thingname.real %R"
    exec {fd}<&2; time ( $@ 2>&$fd; ) 2>> $out/metrics; exec {fd}<&-
  else
    "$@"
  fi
}

mkdir $out
performance-metrics "simple-echo" echo hello
''
$ nix-build metrics.nix
these derivations will be built:
  /nix/store/npgf9igg0rg3d0njnbvxz0g9935301mf-test-metrics.drv
building '/nix/store/npgf9igg0rg3d0njnbvxz0g9935301mf-test-metrics.drv'...
hello
/nix/store/mvy92i4hsncjwrz3lq6bmwcgz47nbpyr-test-metrics
$ cat result/metrics
time.simple-echo.user 0.000
time.simple-echo.system 0.000
time.simple-echo.real 0.000
$ nix-info
system: "x86_64-darwin", multi-user?: yes, version: nix-env (Nix) 2.0.4, channels(me): "darwin, nixpkgs-18.09pre149653.dc1b036c962", channels(root): "", nixpkgs: /Users/me/.nix-defexpr/channels/nixpkgs