Ensure that the correct stats are registered for the Manager and the api
respectively. E.g. all checkout counters are for the api only, whereas
clone times belong to the manager.
Also new ondemand functionality stats weren't registered, so add these
along with missing delete stats.
Review changes suggested to revise the Metrics related files into a more
logical class structure.
Also fixup grammar typos in docs strings and any trailing metrics that
have been recently added to vmpooler.
This is a re-architect of the vmpooler initialisation code to:
1. Allow an API service for both manager and the api
2. Add the Prometheus endpoints to the web service.
Needed to change the way the Rack Service is started as instantiating
using ".New" leads to a failure to initialise the http Stats
collection.
3. Selectively load the pooler api and/or Prometheus endpoints.
4. Rework API Spec tests for revised API loading. Needed to tidy up the
initialisation and perform a reset! after each test to avoid "leaks"
and dependencies between the tests.
This change adds a capability to vmpooler to provision instances on
demand. Without this change vmpooler only supports retrieving machines
from pre-provisioned pools.
Additionally, this change refactors redis interactions to reduce round
trips to redis. Specifically, multi and pipelined redis commands are
added where possible to reduce the number of times we are calling redis.
To support the redis refactor the redis interaction has changed to
leveraging a connection pool. In addition to offering multiple
connections for pool manager to use, the redis interactions in pool
manager are now thread safe.
Ready TTL is now a global parameter that can be set as a default for all
pools. A default of 0 has been removed, because this is an unreasonable
default behavior, which would leave a provisioned instance in the pool
indefinitely.
Pool empty messages have been removed when the pool size is set to 0.
Without this change, when a pool was set to a size of 0 the API and pool
manager would both show that a pool is empty.
