* Register builds as GC roots so they don't get deleted.

src/Hydra/lib/Hydra/Helper/Nix.pm

@@ -2,11 +2,13 @@ package Hydra::Helper::Nix;
 
 use strict;
 use Exporter;
+use File::Path;
 use File::Basename;
 
 our @ISA = qw(Exporter);
 our @EXPORT = qw(
     isValidPath getHydraPath getHydraDBPath openHydraDB
+    registerRoot getGCRootsDir
     getPrimaryBuildsForReleaseSet getRelease getLatestSuccessfulRelease );
 
 
@@ -42,6 +44,28 @@ sub openHydraDB {
 }
 
 
+sub getGCRootsDir {
+    die unless defined $ENV{LOGNAME};
+    return "/nix/var/nix/gcroots/per-user/$ENV{LOGNAME}/hydra-roots";
+}
+
+
+sub registerRoot {
+    my ($path) = @_;
+
+    my $gcRootsDir = getGCRootsDir;
+    
+    mkpath($gcRootsDir) if !-e $gcRootsDir;
+
+    my $link = "$gcRootsDir/" . basename $path;
+        
+    if (!-l $link) {
+        symlink($path, $link)
+            or die "cannot create symlink in $gcRootsDir to $path";
+    }
+}
+
+
 sub attrsToSQL {
     my ($attrs, $id) = @_;
     my @attrs = split / /, $attrs;

src/Hydra/script/hydra_build.pl

@@ -25,6 +25,8 @@ sub doBuild {
 
     my $errormsg = undef;
     
+    registerRoot $outPath;
+    
     if (!isValidPath($outPath)) {
         $isCachedBuild = 0;
 

src/Hydra/script/hydra_scheduler.pl

@@ -248,6 +248,9 @@ sub checkJob {
                 , sha256hash => $input->{sha256hash}
                 });
         }
+
+        # !!! this should really by done by nix-instantiate to prevent a GC race.
+        registerRoot $drvPath;
     });
 };
 

src/Hydra/script/hydra_update_gc_roots.pl

@@ -9,25 +9,12 @@ use POSIX qw(strftime);
 
 my $db = openHydraDB;
 
-die unless defined $ENV{LOGNAME};
-my $gcRootsDir = "/nix/var/nix/gcroots/per-user/$ENV{LOGNAME}/hydra-roots";
-
 
 my %roots;
 
 sub registerRoot {
     my ($path) = @_;
-    #print "$path\n";
+    Hydra::Helper::Nix::registerRoot($path);
-
-    mkpath($gcRootsDir) if !-e $gcRootsDir;
-
-    my $link = "$gcRootsDir/" . basename $path;
-        
-    if (!-l $link) {
-        symlink($path, $link)
-            or die "cannot create symlink in $gcRootsDir to $path";
-    }
-
     $roots{$path} = 1;
 }
 
@@ -97,11 +84,14 @@ my @buildsToKeep = $db->resultset('Builds')->search({finished => 1, keep => 1},
 keepBuild $_ foreach @buildsToKeep;
 
 
-# For scheduled builds, we register the derivation as a GC root.
+# For scheduled builds, we register the derivation and the output as a GC root.
 print "*** looking for scheduled builds\n";
 foreach my $build ($db->resultset('Builds')->search({finished => 0}, {join => 'schedulingInfo'})) {
     if (isValidPath($build->drvpath)) {
+        print "keeping scheduled build ", $build->id, " (",
+            strftime("%Y-%m-%d %H:%M:%S", localtime($build->timestamp)), ")\n";
         registerRoot $build->drvpath;
+        registerRoot $build->outpath;
     } else {
         print STDERR "warning: derivation ", $build->drvpath, " has disappeared\n";
     }
@@ -109,6 +99,10 @@ foreach my $build ($db->resultset('Builds')->search({finished => 0}, {join => 's
 
 
 # Remove existing roots that are no longer wanted.  !!! racy
+print "*** removing unneeded GC roots\n";
+
+my $gcRootsDir = getGCRootsDir;
+
 opendir DIR, $gcRootsDir or die;
 
 foreach my $link (readdir DIR) {