If this isn't installed, celery workers never see the sample_task used
for the extended heartbeat api call. Since the celery heartbeat check is
turned on by default, we should also make sure this djangoapp and thus
sample_task is installed by default.
Currently, the default configuration causes extended heartbeat to be broken by default.
*Sandbox URL*: TBD - sandbox is being provisioned.
*Merge deadline*: None
1. deploy edx-platform *on latest master* with the default configuration (ie. no overrides/additions for the installed apps or extended heartbeat checks).
2. visit the extended heartbeat api endpoint (`/heartbeat?extended=true`)
3. verify that the celery heartbeat check is present and fails with `"message": "expired"`
4. verify that `KeyError: u'openedx.core.djangoapps.heartbeat.tasks.sample_task'` is shown in the logs
5. apply the patch from this branch and restart/redeploy the devstack.
*Author notes and concerns*:
it is recommended to test this on a local devstack rather than the sandbox (haproxy configuration hides the response when it fails, and ocim adds overrides to installed_apps and extended heartbeat checks by default). If running on a sandbox, you will need to check the extended heartbeat api call locally on the sandbox - eg. `curl localhost:80/heartbeat?extended=true`
[ ] @viadanna
[ ] edX reviewer[s] TBD