The `mock_driver` is an internal task driver used mostly for testing and
simulating workloads. During the allocrunner v2 work (#4792) its name
changed from `mock_driver` to just `mock` and then back to
`mock_driver`, but the fingreprint key was kept as `driver.mock`.
This results in tasks configured with `driver = "mock"` to be scheduled
(because Nomad thinks the client has a task driver called `mock`), but
fail to actually run (because the Nomad client can't find a driver
called `mock` in its catalog).
Fingerprinting the right name prevents the job from being scheduled in
the first place.
Also removes mentions of the mock driver from documentation since its an
internal driver and not available in any production release.
* drivers: plumb hardware topology via grpc into drivers
This PR swaps out the temporary use of detecting system hardware manually
in each driver for using the Client's detected topology by plumbing the
data over gRPC. This ensures that Client configuration is taken to account
consistently in all references to system topology.
* cr: use enum instead of bool for core grade
* cr: fix test slit tables to be possible
Before this change, Client had 2 copies of the config object: config and configCopy. There was no guidance around which to use where (other than configCopy's comment to pass it to alloc runners), both are shared among goroutines and mutated in data racy ways. At least at one point I think the idea was to have `config` be mutable and then grab a lock to overwrite `configCopy`'s pointer atomically. This would have allowed alloc runners to read their config copies in data race safe ways, but this isn't how the current implementation worked.
This change takes the following approach to safely handling configs in the client:
1. `Client.config` is the only copy of the config and all access must go through the `Client.configLock` mutex
2. Since the mutex *only protects the config pointer itself and not fields inside the Config struct:* all config mutation must be done on a *copy* of the config, and then Client's config pointer is overwritten while the mutex is acquired. Alloc runners and other goroutines with the old config pointer will not see config updates.
3. Deep copying is implemented on the Config struct to satisfy the previous approach. The TLS Keyloader is an exception because it has its own internal locking to support mutating in place. An unfortunate complication but one I couldn't find a way to untangle in a timely fashion.
4. To facilitate deep copying I made an *internally backward incompatible API change:* our `helper/funcs` used to turn containers (slices and maps) with 0 elements into nils. This probably saves a few memory allocations but makes it very easy to cause panics. Since my new config handling approach uses more copying, it became very difficult to ensure all code that used containers on configs could handle nils properly. Since this code has caused panics in the past, I fixed it: nil containers are copied as nil, but 0-element containers properly return a new 0-element container. No more "downgrading to nil!"
Port some integration tests of driver fingerprinting.
Some tests (e.g. `TestFingerprintManager_Run_DriversInBlacklist`) have
been subsituted by more isolated tests in
`client/pluginmanager/drivermanager/manager_test.go`
