Comment 26 for bug 1372049

Automatic expansion of thread pool in oslo.messaging is not an option since we should have some limit applied to avoid other problems due to too high parallelism. If we will ever consider expansion of the pool beyond the hardcoded value from the configuration file, we'll need to apply some non-obvious heuristics to determine whether higher parallelism will be beneficial for the whole system.

We may change the default value for oslo.messaging eventlet executor, though it will influence all the services that use the library, not just this specific case, and it's not obvious whether it won't introduce other issues.

The safest option is to backport the Nova fix to stable branches.

I've requested juno and icehouse backports for the Nova patch:
- https://review.openstack.org/132202 (Juno)
- https://review.openstack.org/132218 (Icehouse)