SQLite manifest cache. The DBI AutoCommit feature caused every
process to have an active transaction at all times, which could
indefinitely block processes wanting to update the manifest cache.
* Disable fsync() in the manifest cache because we don't need
integrity (the cache can always be recreated if it gets corrupted).
them into memory. This brings memory use down to (more or less)
O(1). For instance, on my test case, the maximum resident size of
download-using-manifests while filling the DB went from 142 MiB to
11 MiB.
This significantly speeds up the download-using-manifests
substituter, especially if manifests are very large. For instance,
one "nix-build -A geeqie" operation that updated four packages using
binary patches went from 18.5s to 1.6s. It also significantly
reduces memory use.
The cache is kept in /nix/var/nix/manifests/cache.sqlite. It's
updated automatically when manifests are added to or removed from
/nix/var/nix/manifests. It might be interesting to have nix-pull
store manifests directly in the DB, rather than storing them as
separate flat files, but then we would need a command line interface
to delete manifests from the DB.
`+' and `?' in filenames. This is very slow if /nix/store is very
large. (This is a quick hack - a cleaner solution would be to
bypass the shell entirely.)
`nix-store -q --hash' to get the hash of the base path rather than
`nix-hash'. However, only do this for estimating the size of a
download, not for the actual substitution, because sometimes the
contents of store paths are modified (which they shouldn't, of
course).
hook script proper, and the stdout/stderr of the builder. Only the
latter should be saved in /nix/var/log/nix/drvs.
* Allow the verbosity to be set through an option.
* Added a flag --quiet to lower the verbosity level.
it requires a certain feature on the build machine, e.g.
requiredSystemFeatures = [ "kvm" ];
We need this in Hydra to make sure that builds that require KVM
support are forwarded to machines that have KVM support. Probably
this should also be enforced for local builds.
the hook every time we want to ask whether we can run a remote build
(which can be very often), we now reuse a hook process for answering
those queries until it accepts a build. So if there are N
derivations to be built, at most N hooks will be started.
