refactor(ops/pipelines): Move :anchor: into postBuildSteps r/3659

There is no need for this step to be part of the static pipeline (it
should not run if the build fails anyways).

Change-Id: I71400a452d6f8f4708d146b346eaffda5da2f766
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5049
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: ezemtsov <eugene.zemtsov@gmail.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/ops/pipelines/depot.nix b/ops/pipelines/depot.nix
index 036ddada0ed7..b6941ba38aa7 100644
--- a/ops/pipelines/depot.nix
+++ b/ops/pipelines/depot.nix
@@ -19,6 +19,24 @@ let
     parentTargetMap = if (externalArgs ? parentTargetMap)
       then builtins.fromJSON (builtins.readFile externalArgs.parentTargetMap)
       else {};
+
+    postBuildSteps = [
+      # After successful builds, create a gcroot for builds on canon.
+      #
+      # This anchors *most* of the depot, in practice it's unimportant
+      # if there is a build race and we get +-1 of the targets.
+      #
+      # Unfortunately this requires a third evaluation of the graph, but
+      # since it happens after :duck: it should not affect the timing of
+      # status reporting back to Gerrit.
+      {
+        label = ":anchor:";
+        branches = "refs/heads/canon";
+        command = ''
+          nix-build -A ci.gcroot --out-link /nix/var/nix/gcroots/depot/canon
+        '';
+      }
+    ];
   };
 
   drvmap = depot.nix.buildkite.mkDrvmap depot.ci.targets;