Open Stack

On 2021-01-19 12:56:41 +0000 (+0000), Sean Mooney wrote:
> On Tue, 2021-01-19 at 12:37 +0100, Dmitry Tantsur wrote:
[...]
> > I wonder if we could also run the plugin that shows the live
> > progress (it was mentioned somewhere in the thread).
> 
> i belive showing the live progress of the jobs is effectivly a
> ddos vector. infra have ask that we not use javascript to pool the
> the live status of the jobs in our browser in the past.
[...]
> i know that we previously tried enbeding the zuul job status
> directly into gerrit a few years ago and that had to be qickly
> reverted as it does not take many developers leave review open in
> a tab to quickly make that unworkable. i know i for one often
> leave review open over night if im pinged to review something
> shortly before i finish for the day so that its open on my screen
> when i log in the next day.
[...]

I think it's probably worth trying again. The previous attempts hit
a wall because of several challenges:

1. The available Zuul status API returned data on all enqueued refs
(a *very* large JSON blob when the system is under heavy use)

2. Calls to the API were handled by a thread of the scheduler
daemon, so often blocked or were blocked by other things going on,
especially when Zuul was already under significant load

3. Browsers at the time continued running Javascript payloads in
"background" tabs so the volume of queries was multiplied not just
by the number of users but also by the average number of review tabs
they had open

Over time we added a ref-scoped status method so callers could
request the status of a specific change. The Zuul REST API is now
served by a separate zuul-web daemon, which we can move to a
different server entirely if load demands that (and can even scale
horizontally with more than one instance of it, I think?). Browser
tech has also improved, and popular ones these days suspend
Javascript stacks when tabs are not exposed. We may also be caching
status API responses more aggressively than we used to do. All of
these factors combined could make live status info in a Gerrit
plug-in entirely tractable, we'll just need someone with time to try
it and see... and be prepared for multiple Gerrit service restarts
to enable/disable it, so probably not when utilization is as high as
it has been the past couple of weeks.
-- 
Jeremy Stanley
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