These are build steps that remain "busy" in the database even though
they have finished, because they couldn't be updated (e.g. due to a
PostgreSQL connection problem). To prevent them from showing up as
busy in the "Machine status" page, we now periodically purge them.
Previously, if the queue monitor thread encounters a build that Hydra
has previously built, it downloaded the output paths from the binary
cache, just to determine the build products and metrics. This is very
inefficient. In particular, when doing something like merging
nixpkgs:staging into nixpkgs:master, the queue monitor thread will be
locked up for a long time fetching files from S3, causing the build
farm to be mostly idle.
Of course this is entirely unnecessary, since the build
products/metrics are already in the Hydra database. So now we just
look up a previous build with the same output path, and copy the
products/metrics.
Mutliple <githubstatus> sections are possible:
* jobs: regexp for jobs to match
* inputs: the input which corresponds to the github repo/rev whose
status we want to report. Can be repeated
* authorization: Verbatim contents of the Authorization header. See
https://developer.github.com/v3/#authentication.
Otherwise, the browser may mix up HTML and JSON responses if it has
requested both. For example, hitting the back button to return to a
job metric page will show a JSON response, because that was the last
thing the browser fetched for that URL.
This requires Catalyst::Action::Rest >= 1.20.
The previous query
select count(*) from builds b left join buildsteps s on s.build = b.id where busy = 1 and finished = 0
is suddenly taking several minutes. Probably PostgreSQL decided to use
a suboptimal query plan.
