* Register GC roots properly.

src/script/hydra_build.pl

@@ -28,8 +28,6 @@ sub doBuild {
     my $failedDepBuild;
     my $failedDepStepNr;
     
-    registerRoot $outPath;
-    
     if (!isValidPath($outPath)) {
         $isCachedBuild = 0;
 
@@ -75,7 +73,8 @@ sub doBuild {
         # to get notifications about specific build steps, the
         # associated log files, etc.
         my $cmd = "nix-store --max-silent-time 1800 --keep-going --no-build-output " .
-            "--log-type flat --print-build-trace --realise $drvPath 2>&1";
+            "--log-type flat --print-build-trace --realise $drvPath " .
+            "--add-root " . gcRootFor $outPath . " 2>&1";
 
         my $buildStepNr = 1;
         

src/script/hydra_scheduler.pl

@@ -267,9 +267,6 @@ sub checkJob {
                 , sha256hash => $input->{sha256hash}
                 });
         }
-        
-        # !!! this should really by done by nix-instantiate to prevent a GC race.
-        registerRoot $drvPath;
     });
 };
 
@@ -330,9 +327,12 @@ sub checkJobSet {
     $nixExprPath .= "/" . $jobset->nixexprpath;
 
     (my $res, my $jobsXml, my $stderr) = captureStdoutStderr(
-        "hydra_eval_jobs", $nixExprPath, inputsToArgs($inputInfo));
+        "hydra_eval_jobs", $nixExprPath, "--gc-roots-dir", getGCRootsDir,
+        inputsToArgs($inputInfo));
     die "cannot evaluate the Nix expression containing the jobs:\n$stderr" unless $res;
 
+    print STDERR "$stderr";
+
     my $jobs = XMLin($jobsXml,
                      ForceArray => ['error', 'job', 'arg'],
                      KeyAttr => [],

src/script/hydra_update_gc_roots.pl

@@ -83,14 +83,14 @@ my @buildsToKeep = $db->resultset('Builds')->search({finished => 1, keep => 1},
 keepBuild $_ foreach @buildsToKeep;
 
 
-# For scheduled builds, we register the derivation and the output as a GC root.
+# For scheduled builds, we register the derivation as a GC root.
 print STDERR "*** looking for scheduled builds\n";
 foreach my $build ($db->resultset('Builds')->search({finished => 0}, {join => 'schedulingInfo'})) {
     if (isValidPath($build->drvpath)) {
         print STDERR "keeping scheduled build ", $build->id, " (",
             strftime("%Y-%m-%d %H:%M:%S", localtime($build->timestamp)), ")\n";
         registerRoot $build->drvpath;
-        registerRoot $build->outpath;
+        registerRoot $build->outpath if -e $build->outpath;
     } else {
         print STDERR "warning: derivation ", $build->drvpath, " has disappeared\n";
     }