x/build/cmd/tip: deploy instructions for talks.golang.org are non-functional

[dmitshur]

(Factoring this out from #36825 to describe this problem in more detail, without derailing the higher level decision in that issue.)

The deploy instructions for talks.golang.org that are in the x/cmd/tip README have become outdated and cannot be used today.

Doing gcloud --project golang-org app deploy --no-promote talks.yaml in x/build/cmd/tip directory results in:

ERROR: (gcloud.app.deploy) INVALID_ARGUMENT: Legacy health checks are no longer supported for the App Engine Flexible environment. Please remove the 'health_check' section from your app.yaml and configure updated health checks. For instructions on migrating to split health checks see https://cloud.google.com/appengine/docs/flexible/java/migrating-to-split-health-checks

That is easily fixable with:

--- a/cmd/tip/talks.yaml
+++ b/cmd/tip/talks.yaml
@@ -8,5 +8,7 @@ manual_scaling:
 env_variables:
   TIP_BUILDER: 'talks'
 
-health_check:
-  enable_health_check: False
+liveness_check:
+  path: /_ah/health
+readiness_check:
+  path: /_ah/health

The next problem is that the Dockerfile in x/build/cmd/tip directory was modified in CL 176257 with the assumption that it would be called with the x/build root directory as the working directory. That CL modified cmd/tip/Makefile like this:

 docker-image: Dockerfile *.go
-	docker build --force-rm -f Dockerfile --tag=$(IMAGE_PROD):$(VERSION) .
+	docker build --force-rm -f Dockerfile --tag=$(IMAGE_PROD):$(VERSION) ../..

However, that's not compatible with the App Engine-based deploy for talks.golang.org, because doing gcloud app deploy in x/build/cmd/tip causes Cloud Build to try to run Dockerfile with x/build/cmd/tip as the working directory, so statements like COPY go.mod /go/src/golang.org/x/build/go.mod produce errors:

Step #1: Step 6/20 : COPY go.mod /go/src/golang.org/x/build/go.mod
Step #1: COPY failed: stat /var/lib/docker/tmp/docker-builder636121389/go.mod: no such file or directory

/cc @cagedmantis @toothrot @andybons

[dmitshur]

I revisited and investigated this in some depth last week.

As a reminder, the tip.golang.org website was migrated from App Engine to GKE in CL 37754, but doing the same migration for the talks server was left as a TODO.

That means there are two paths to fix x/build/cmd/tip deployment for talks:

1. stay with App Engine and fix the paths (without breaking tip.golang.org in the process)
2. complete the TODO to move talks.golang.org to GKE

I primarily investigated path 2, and did the work of completing the migration to GKE on a staging instance. It worked. However, I found that there's some overhead in updating the DNS entries that would need to be done if we move the talks.golang.org deployment to GKE.

In the end, it seems better to make the decision in #36825 to stick with deployment instructions in x/talks README, and remove the x/build/cmd/tip version for now. If we need to, we can bring it back in the future. Closing because there's nothing more to do here for now.

[gopherbot]

Change https://golang.org/cl/290529 mentions this issue: cmd/tip: remove ability to serve talks.golang.org