Fix race between hydra-eval-jobs and hydra-update-gc-roots

Dependencies

• [2] PMNWRTGJ Add multiple output support
• [3] ACFFJUAN hydra-update-gc-roots: Keep more evals
• [4] WZ3AEJ67 * hydra_update_gc_roots.pl registers build outputs that should be kept
• [5] FP72ASZX No wonder our disk was filling up
• [6] IN272KZW * Automatically keep all builds in the latest successful release in
• [7] KJQWSRCC Speed up hydra-update-gc-roots
• [8] SZPBGW2N Fix a race condition in hydra-update-gc-roots
• [9] 4X6NS66Q * Keep the most recent builds for each job.

Change contents

• edit in src/script/hydra-update-gc-roots at line 5
  [3.544]

  [3.544]
  + use File::stat;
• replacement in src/script/hydra-update-gc-roots at line 52
  [3.1148]→[3.0:149](∅→∅)
  − # Read the current GC roots. We need to do that here so that we don't

  − # delete roots that were added while we were determining the desired

  − # roots.
  [3.1148]

  [3.149]
  + # Read the current GC roots.
• edit in src/script/hydra-update-gc-roots at line 124
  [3.2766]

  [3.2064]
  + my $now = time();
• replacement in src/script/hydra-update-gc-roots at line 130
  [3.2221]→[3.2221:2267](∅→∅),[3.2267]→[2.19656:19681](∅→∅),[2.19681]→[3.0:78](∅→∅),[3.2864]→[3.0:78](∅→∅)
  − print STDERR "removing root $path\n";

  − $rootsDeleted++;

  − unlink "$gcRootsDir/$link" or warn "cannot remove $gcRootsDir/$link";
  [3.2221]

  [3.2942]
  + # Don't delete roots that are less than a day old, to prevent

  + # a race where hydra-eval-jobs has added a root but

  + # hydra-evaluator hasn't added them to the database yet.

  + if (lstat($path)->ctime < $now - 24 * 60 * 60) {

  + print STDERR "removing root $path\n";

  + $rootsDeleted++;

  + unlink "$gcRootsDir/$link" or warn "cannot remove $gcRootsDir/$link";

  + } else {

  + print STDERR "NOT removing recent root $path\n";

  + $rootsKept++;

  + }