If the ifcmd returns true and this option is set, it will match that
output against this field, and if they match, then we skip cmd.
Much cleaner than needing to invoke bash to compare two strings.
This was a long time coming, but now it looks to be done. It was kind of
meant as low-hanging fruit for some interested student, but in the end I
got to it first.
This was really not ever tested properly, and I worry it will deadlock.
It definitely kicks off falls positives that don't even do any harm as
far as we can tell.
There was and still is a bunch of terrible mess in this code. This does
some initial cleanup, and also fixes an important bug!
If you're provisioning a vmhost from scratch, then the function engine
might do some work to get the libvirt related services running before
the virt resource is used to build a vm. Since we had connection code in
Init() it would fail if it wasn't up already, meaning we'd have to write
fancy mcl code to avoid this, or we could do this refactor and keep
things more logical.
These are expected from our engine. We do care about timeout's and so
on. This allows os to return ctx.Err() whenever a <-ctx.Done() happens,
which is more idiomatic for what we really want, but which we weren't
thorough with before.
This mega patch primarily introduces a new function engine. The main
reasons for this new engine are:
1) Massively improved performance with lock-contended graphs.
Certain large function graphs could have very high lock-contention which
turned out to be much slower than I would have liked. This new algorithm
happens to be basically lock-free, so that's another helpful
improvement.
2) Glitch-free function graphs.
The function graphs could "glitch" (an FRP term) which could be
undesirable in theory. In practice this was never really an issue, and
I've not explicitly guaranteed that the new graphs are provably
glitch-free, but in practice things are a lot more consistent.
3) Simpler graph shape.
The new graphs don't require the private channels. This makes
understanding the graphs a lot easier.
4) Branched graphs only run half.
Previously we would run two pure side of an if statement, and while this
was mostly meant as an early experiment, it stayed in for far too long
and now was the right time to remove this. This also means our graphs
are much smaller and more efficient too.
Note that this changed the function API slightly. Everything has been
ported. It's possible that we introduce a new API in the future, but it
is unexpected to cause removal of the two current APIs.
In addition, we finally split out the "schedule" aspect from
world.schedule(). The "pick me" aspects now happen in a separate
resource, rather than as a yucky side-effect in the function. This also
lets us more precisely choose when we're scheduled, and we can observe
without being chosen too.
As usual many thanks to Sam for helping through some of the algorithmic
graph shape issues!
If the user is logged in, and we try to change from /home/james to
/home/james/ we'll get the error:
usermod: user james is currently used by process ????
and furthermore, it makes no sense to try and make this change since the
usermod function won't do anything if you run:
usermod --gid james --groups wheel --home /home/james/ james
when /etc/passwd has /home/james as the string.
If we want to receive more than on flag (key) value, then these
obviously need to autogroup together, because it's the same http server
request that comes in and which should be shared by everyone with the
same path.
This should ensure this sort order of longer thing first, when running
the algorithm. We want to autogroup two or more http:server:flag
resources together first, before the whole grouped resource gets pulled
into the http:server one.
Not sure why I was blocking this previously, perhaps there was no use
case, and I was trying to ensure there wasn't accidental, unwanted
grouping? Perhaps I wanted to improve performance? In any case, let's
turn this off for now, and check for bugs.
These can "break" silently and not autogroup if we change the resource
and it no longer fulfills the interface. Add this compile time check to
prevent that.
Resources that can be grouped into the http:server resource must have
that prefix. Grouping is basically hierarchical, and without that common
prefix, it means we'd have to special-case our grouping algorithm.
