playground: slurp binary to memory in gvisor mode

Slurp the binary to memory before POSTing it. This simplifies retries
a bit (doesn't need to re-open the file) and sets a Content-Length
header, and checks the file size early, rather than having the backend

None of this should matter for correctness (and unnecessarily uses
more memory than before), but we're sometimes seeing timeout errors
followed by this frontend returning (and caching!) an empty response
where the backend never sees a binary arrive, so this is somewhat a
shot in the dark for now. Something's up with our internal load
balancer, perhaps. Still debugging.

Also update/add some comments.

Updates golang/go#25224

Change-Id: I12f08db8ac77743b555fe7ef56bccf8cbc45742c
Reviewed-by: Alexander Rakoczy <>
1 file changed
tree: acc8cd2d7a43ac5ef20ed6b3d93dbc334d0cc847
  1. cmd/
  2. deploy/
  3. sandbox/
  4. static/
  5. .gitignore
  6. app.yaml
  8. cache.go
  9. client.go
  10. codereview.cfg
  13. Dockerfile
  14. edit.go
  15. edit.html
  16. enable-fake-time.patch
  17. fake_fs.lst
  18. fmt.go
  19. fmt_test.go
  20. go.mod
  21. go.sum
  23. logger.go
  24. main.go
  25. Makefile
  27. play.go
  28. play_test.go
  30. sandbox.go
  31. server.go
  32. server_test.go
  33. share.go
  34. store.go
  35. tests.go
  36. txtar.go
  37. txtar_test.go
  38. vet.go


This subrepository holds the source for the Go playground:


# build the image
docker build -t playground .


docker run --name=play --rm -p 8080:8080 golang/playground &
# run some Go code
cat /path/to/code.go | go run client.go | curl -s --upload-file - localhost:8080/compile


Deployment Triggers

Playground releases automatically triggered when new Go repository tags are pushed to GitHub, or when master is pushed on the playground repository.

For details, see deploy/go_trigger.json, deploy/playground_trigger.json, and deploy/deploy.json.

After making changes to trigger configuration, update configuration by running the following Make target:

make update-cloudbuild-trigger

Deploy via Cloud Build

The Cloud Build configuration will always build and deploy with the latest supported release of Go.

gcloud builds submit --config deploy/deploy.json .

Deploy via gcloud app deploy

Building the playground Docker container takes more than the default 10 minute time limit of cloud build, so increase its timeout first (note, app/cloud_build_timeout is a global configuration value):

gcloud config set app/cloud_build_timeout 1200  # 20 mins

Alternatively, to avoid Cloud Build and build locally:

make docker
docker tag golang/playground:latest
docker push
gcloud --project=golang-org app deploy app.yaml


gcloud --project=golang-org app deploy app.yaml


To submit changes to this repository, see