_frontend/app.py: Set correct element-path in interactive bst-init

See merge request !912

Benjamin Schubert authored Oct 19, 2018 and Benjamin Schubert committed Nov 01, 2018

This includes a new command mimicking pytest-runner so that we
can drop this dependency

This was the only setup_requires dependency that we had and
will make like easier for people behind proxies

Remove dependency on pytest-runner

See merge request !886

The file is already a temporary file and does not need copy.  ENOSPC
is thrown during that copy in issue #609.

Fixes #678.

There were some race conditions in the way we store artifacts in the
server. Now we verify we still have space on disk for every write. We
also handle ENOSPC to reallocate space or if we cannot properly fail
the connection.

This should help for #609.

Issue was found while investigating for #609. When the disk gets
filled up, we would prune non-referenced objects. Since this happens
during an upload of object before a reference is added for uploaded
objects, then we would have an incomplete upload. Further pulls would
result in a missing object error.

The solution is to let 6 hours pass before we can prune an object.  To
implement this fix without this minimum age "trick", we would need to
change protocol and deal with concurrent pushes.

We plan to make cache incomplete. That is some blobs are missing.  For
most of cases we will delete references when requested if they are
incomplete. But there will be corner cases where objects are removed
after the reference is requested.

This also remove references when some objects are missing. This is in
preparation for the move from reference to object garbage collection.

f_bfree space might not be usable. In practice we see failures in big
disks because f_bfree is over 2GB and f_bavail is 0. We get ENOSPC if
writing on disk then.

Also add locking to not collect in parallel. Collect a bit more than
needed. Make the cache sizes configurable.