Hi out there,
Over the past couple of weeks, I started working on a new ContainerPool (and
thus eventually a new Invoker). It started as a weekend investigation into how
one would write the Invoker if one started on a green field and turned out a
valuable step forward after all.
The new ContainerPool is modeled around Akka Actors and I put an emphasis on the testability of the
code. Before diving deeper into performance work on OpenWhisk we need to be able to quickly verify
new models of scheduling and thus I abstracted the "container providing" code away from
the pool itself. One can now easily simulate different workloads without actually talking to docker
itself. A nice side-effect of this is, that the Container interface (it's literally a trait) is
completely pluggable and can also be filled in by
"insert-your-favorite-container-solution-here".
In terms of performance I did see a significant improvement in single-user
throughput performance but haven't yet got around to make a proper write-up of
the experiment's setup and methodology, hence I'll not show hard numbers for
now. We're still missing out on a common load test suite which we can all use
to verify our changes.
So all in all features:
- Eliminated concurrency behavior through the actor model
- Eliminated busy looping to get a container
- Increased testability by drawing sharp-abstraction layers and making sure
each component is testable separately
- Increased "experimentability" with scheduling algorithms (they are
encapsulated themselves)
- Performance increases very likely due implementation of a "pause grace" (the
container is not paused for a defined amount of time and can continue its work
immediately if another request comes in at that time)
- Pluggability of the container interface
The pull-request is open at https://github.com/openwhisk/openwhisk/pull/2021.
It's passing tests already. Test coverage is still a bit low, but Sven
Lange-Last and I are working to get it done quite soon.
It will be delivered in multiple smallish pull-requests, the first of which is
open here: https://github.com/openwhisk/openwhisk/pull/2092. At first, the new
pool is going to be behind a feature flag. Once the pool has battle proven, we
can then flip the switch and remove old code as applicable.
Feel free to have a play with it, feedback and code-reviews are very very
welcome!
Cheers,
Markus
