Tools like `nomad-nodesim` are unable to implement a minimal implementation of
an allocrunner so that we can test the client communication without having to
lug around the entire allocrunner/taskrunner code base. The allocrunner was
implemented with an interface specifically for this purpose, but there were
circular imports that made it challenging to use in practice.
Move the AllocRunner interface into an inner package and provide a factory
function type. Provide a minimal test that exercises the new function so that
consumers have some idea of what the minimum implementation required is.
This PR fixes various instances of plugins being launched without using
the parent loggers. This meant that logs would not all go to the same
output, break formatting etc.
Tons left to do and lots of churn:
1. No state saving
2. No shutdown or gc
3. Removed AR factory *for now*
4. Made all "Config" structs local to the package they configure
5. Added allocID to GC to avoid a lookup
Really hating how many things use *structs.Allocation. It's not bad
without state saving, but if AllocRunner starts updating its copy things
get racy fast.
WARNing when someone has over 50 non-terminal allocs was just too
confusing.
Tested manually with `gc_max_allocs = 10` and bumping a job from `count
= 19` to `count = 21`:
```
2017/11/02 17:54:21.076132 [INFO] client.gc: garbage collection due to number of allocations (19) is over the limit (10) skipped because no terminal allocations
...
2017/11/02 17:54:48.634529 [WARN] client.gc: garbage collection due to number of allocations (21) is over the limit (10) skipped because no terminal allocations
```
The Client.allocs map now contains all AllocRunners again, not just
un-GC'd AllocRunners. Client.allocs is only pruned when the server GCs
allocs.
Also stops logging "marked for GC" twice.
This PR introduces a parallelism limit during garbage collection. This
is used to avoid large resource usage spikes if garbage collecting many
allocations at once.
