This PR adds a `WatchAllWorkspaces` function with `watch-all-workspaces`
endpoint, which can be used to listen on a single global pubsub channel
for _all_ workspace build updates, and makes use of it in the autostart
scaletest.
This negates the need to use a workspace watch pubsub channel _per_
workspace, which has auth overhead associated with each call. This is
especially relevant in situations such as the autostart scaletest, where
we need to start/stop a set of workspaces before we can configure their
autostart config. The overhead associated with all the watch requests
skews the scaletest results and makes it harder to reason about the
performance of the autostart feature itself.
The autostart scaletest also no longer generates its own metrics nor
does it wait for all the workspaces to actually start via autostart. We
should update the scaletest dashboard after both PRs are merged to
measure autostart performance via the new metrics.
The new function/endpoint and its usage in the autostart scaletest are
gated behind an experiment feature flag, this is something we should
discuss whether we want to enable the endpoint in prod by default or
not. If so, we can remove the experiment.
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Signed-off-by: Callum Styan <callumstyan@gmail.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Callum Styan <callum@coder.com>
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