This change adds a new Strategy concept to the daemon module similar to
how we manage WSGI workers. We need to leverage multiple python
processes to get the concurrency properties we need. More workers will
rebalance much faster on dense chassis with many devices.
Currently the default is still only one process, and no workers. Set
reconstructor_workers in the [object-reconstructor] section to some
whole number <= the number of devices on a node to get that many
reconstructor workers.
Each worker will operate on a different subset of disks.
Once mode works as before, but tends to want to update recon drops a
little bit more.
If you change the rings, the strategy will shutdown workers and spawn
new ones.
You can kill the worker pids and the daemon strategy will respawn them.
New per-disk reconstructor stats are dumped to recon under the
object_reconstruction_per_disk key. To maintain legacy compatibility
and replication monitoring based on cycle times they are aggregated
every stats_interval (default 5 mins).
Change-Id: I28925a37f3985c9082b5a06e76af4dc3ec813abe
701a172afa