Without actually simulating cluster implementation at all. Instead, only
the essential fact that cluster gateways know what changes they have
made to each node of a cluster. That is enough for sims like
sizebalanced_cluster.
Probably a good idea for freezing, but especially I hope this fixes a
problem with git-annex sim run that caused it to sometimes crash in
removeDirectoryRecursive with directory not empty, presumably because a
thread was writing there at the same time.
Without any connections, the step command will not try to do any actions
on a special remote.
But even without any connections, it's still possible for a drop action
explicitly run "on" the special remote to do, when numcopies = 0 or
there is a trusted repo. So guard all actions against running on a
special remote too.
Once it has a list of actions, it can perform them all.
A disappointing optimisation at least in my test case, which it sped up
by less than 1 second out of 12. But still it did make it faster.
Noticed that it was quite slow compared with things like action
sendwanted. Guessed that the slowdown is largely due to every step
doing a simulated git pull/push.
So, rather than always doing a pull/push, only do those when no actions
are found without doing a pull/push.
This does mean that step will sometimes experience a split brain
situation, but that seems like a good thing? Because step ought to
explore as many possible scenarios as it reasonably can.
When getting from a remote, have to check that the repo doing the
getting thinks the remote contains the key, but also that the remote
actually does. Before this bug fix, it would get from a repo that used
to have the key, but that had dropped it since the last git pull.
Had to add Read instances to Key and NumCopies and some other similar
types. I only expect to use those in serializing a sim. Of course, this
risks that implementation changes break reading old data. For a sim,
that would not be a big problem.
Not tested yet. This emulates the same checking that is done when
dropping. Note that when dropping from a special remote it is not able
to make a locked copy.
The generator doesn't emit the best possible connect commands,
but it does output something valid. Eg, an input like:
connect A <-> B <-> C <-> D
becomes:
connect A <-> B <-> C
connect C <-> D
Also:
connect A -> B <- C
becomes:
connect A -> B
connect C -> B
Which could be improved.
Also disconnect commands are not prettified at all, but probably there's
no reason to.
These don't actually need to do any git actions, instead they just merge
the simLocations.
Had to make simLocations use a vector clock, because it is possible for
two simulated repositories to end up with different opinions about the
location of a key. Just like with real git-annex, whichever location
change was made most recently wins out.
The vector clock is simply advanced each time the simulation is run for
a step. Since there is no real parallelism in the sim, that's
sufficient.
