Due to the fixed-output derivation hashing scheme, there can be
multiple derivations of the same output path. But build logs are
indexed by derivation path. Thus, we may not be able to find the
log of a build or build step using its derivation. So as a fallback,
Hydra now looks for other derivations with the same output paths.
They're mostly redundant since there is a faster "jobs" tab on
the jobset pages now. The only thing the latter lacks is the
ability to see status change times, but those are quite expensive
to compute, and are visible on build pages if you really need them.
PostgreSQL and Perl have different sort orders, in particular when
comparing job names such as "aspell.x86_64-linux" and
"aspellDicts.cs.i686-freebsd". This confused the evaluation
comparison code, causing some jobs to appear as "removed".
So now we do all the sorting in Perl.
Fixes#105.
Aggregate constituents are derivations. However there can be multiple
builds in an evaluation that have the same derivation, i.e. they can
alias each other (e.g. "emacs", "emacs24" and "emacs24Packages.emacs"
in Nixpkgs). Previously we picked a build arbitrarily for the
AggregateConstituents table. Now we pick the one with the shortest
name (e.g. "emacs").
For presentation purposes, we need to know what builds are part of an
aggregate build. So at evaluation time, look at the "members"
attribute, find the corresponding builds in the eval, and create a
mapping in the AggregateMembers table.
It redirects to the latest successful build from a finished
evaluation. This is mostly useful for the Nixpkgs/NixOS mirroring
script, which need the latest finished evaluation in which some
aggregate job (such as ‘tested’ in NixOS) succeeded.
The NrBuilds table tracks the value of ‘select count(*) from Builds
where finished = 0’, keeping it up to date via a trigger. This is
necessary to make the /all page fast, since otherwise it needs to do a
sequential scan on the Builds table.
Doing a chdir in the parent is evil. For instance, we had Hydra core
dumps ending up in the cloned directory. Therefore, the function
‘run’ allows doing a chdir in the child. The function ‘grab’ returns
the child's stdout and throws an exception if the child fails.
