* Allow scheduled builds to be cancelled. They're not removed from

the database, just marked as cancelled, because otherwise the
  scheduler would just add them again.

src/lib/Hydra/Controller/Build.pm

@@ -30,7 +30,7 @@ sub view_build : Chained('build') PathPart('') Args(0) {
     $c->stash->{curTime} = time;
     $c->stash->{available} = isValidPath $build->outpath;
     $c->stash->{drvAvailable} = isValidPath $build->drvpath;
-    $c->stash->{flashMsg} = $c->flash->{afterRestart};
+    $c->stash->{flashMsg} = $c->flash->{buildMsg};
 
     if (!$build->finished && $build->schedulingInfo->busy) {
         my $logfile = $build->schedulingInfo->logfile;
@@ -156,17 +156,19 @@ sub nix : Chained('build') PathPart('nix') CaptureArgs(0) {
 }
 
 
-sub restart : Chained('build') PathPart('restart') Args(0) {
+sub restart : Chained('build') PathPart Args(0) {
     my ($self, $c) = @_;
 
     my $build = $c->stash->{build};
 
     requireProjectOwner($c, $build->project);
 
-    error($c, "This build cannot be restarted.")
-        unless $build->finished && $build->resultInfo->buildstatus == 3;
-
     $c->model('DB')->schema->txn_do(sub {
+        error($c, "This build cannot be restarted.")
+            unless $build->finished &&
+              ($build->resultInfo->buildstatus == 3 ||
+               $build->resultInfo->buildstatus == 4);
+
         $build->finished(0);
         $build->timestamp(time());
         $build->update;
@@ -181,7 +183,41 @@ sub restart : Chained('build') PathPart('restart') Args(0) {
             });
     });
 
-    $c->flash->{afterRestart} = "Build has been restarted.";
+    $c->flash->{buildMsg} = "Build has been restarted.";
+    
+    $c->res->redirect($c->uri_for($self->action_for("view_build"), $c->req->captures));
+}
+
+
+sub cancel : Chained('build') PathPart Args(0) {
+    my ($self, $c) = @_;
+
+    my $build = $c->stash->{build};
+
+    requireProjectOwner($c, $build->project);
+
+    $c->model('DB')->schema->txn_do(sub {
+        error($c, "This build cannot be cancelled.")
+            if $build->finished || $build->schedulingInfo->busy;
+
+        # !!! Actually, it would be nice to be able to cancel busy
+        # builds as well, but we would have to send a signal or
+        # something to the build process.
+
+        $build->finished(1);
+        $build->timestamp(time());
+        $build->update;
+
+        $c->model('DB::BuildResultInfo')->create(
+            { id => $build->id
+            , iscachedbuild => 0
+            , buildstatus => 4 # = cancelled
+            });
+
+        $build->schedulingInfo->delete;
+    });
+
+    $c->flash->{buildMsg} = "Build has been cancelled.";
     
     $c->res->redirect($c->uri_for($self->action_for("view_build"), $c->req->captures));
 }

src/root/build.tt

@@ -40,12 +40,17 @@
         [% ELSIF build.resultInfo.buildstatus == 2 %]
           <img src="/static/images/failure.gif" alt="Failed" />
           <span class="error">A dependency of the build failed</span>
+        [% ELSIF build.resultInfo.buildstatus == 4 %]
+          <img src="/static/images/failure.gif" alt="Failed" />
+          <span class="error">Cancelled by user</span>
         [% ELSE %]
           <img src="/static/images/failure.gif" alt="Failed" />
           <span class="error">Build failed</span>
           (see <a href="#nix-error">below</a>)
+        [% END %]
+        [% IF build.resultInfo.buildstatus == 3 || build.resultInfo.buildstatus == 4 %]
           <form action="[% c.uri_for('/build' build.id 'restart') %]" method="post" class="inline">
-            <button id="delete-project" type="submit">Restart</button>
+            <button id="restart" type="submit">Restart</button>
           </form>
         [% END %]
       [% ELSIF build.schedulingInfo.busy %]
@@ -53,6 +58,11 @@
         since [% PROCESS renderDateTime timestamp = build.schedulingInfo.starttime %]
       [% ELSE %]
         <strong>Scheduled to be built</strong>
+        [% IF c.user_exists %]
+          <form action="[% c.uri_for('/build' build.id 'cancel') %]" method="post" class="inline">
+            <button id="cancel" type="submit">Cancel</button>
+          </form>
+        [% END %]
       [% END %]
     </td>
   </tr>
@@ -116,7 +126,7 @@
     <th>Time added:</th>
     <td>[% PROCESS renderDateTime timestamp = build.timestamp %]</td>
   </tr>
-  [% IF build.finished %]
+  [% IF build.finished && build.resultInfo.buildstatus != 4 %]
     <tr>
       <th>Build started:</th>
       <td>[% IF build.resultInfo.starttime %][% PROCESS renderDateTime timestamp = build.resultInfo.starttime %][% ELSE %]<em>(cached build)</em>[% END %]</td>
@@ -143,7 +153,8 @@
         </td>
       </tr>
     [% END %]
-  [% ELSE %]
+  [% END %]
+  [% IF !build.finished %]
     <tr>
       <th>Priority:</th>
       <td>[% build.schedulingInfo.priority %]</td>

src/sql/hydra.sql

@@ -61,6 +61,7 @@ create table BuildResultInfo (
     --   1 = build of this derivation failed
     --   2 = build of some dependency failed
     --   3 = other failure (see errorMsg)
+    --   4 = build cancelled (removed from queue; never built)
     buildStatus   integer,
 
     errorMsg      text, -- error message in case of a Nix failure