[GitHub] kpavel opened a new pull request #3886: Proposing Lean OpenWhisk

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kpavel opened a new pull request #3886: Proposing Lean OpenWhisk
URL: https://github.com/apache/incubator-openwhisk/pull/3886
 
 
   The proposition is to get rid of Kafka, have controller and invoker compiled together into a "lean" controller-invoker (have a Gradle project for that) with controller calling the invoker's method directly via an in-memory object (a queue, which is also loaded via SPI) via a new pluggable load balancer that is selected via SPI using configuration file property setting. For more information here is a [blog](https://medium.com/@davidbr_9022/lean-openwhisk-open-source-faas-for-edge-computing-fb823c6bbb9b)
   As well, briefly discussed it in this [thread](https://lists.apache.org/thread.html/516efc0ed9afb09fe52e30d10eb9fe5091af91df53a46c07e1701122@%3Cdev.openwhisk.apache.org%3E)
   
   ## Description
   The goal is to avoid changes in the core components as much as possible. Rather this PR adds a few components. The main additions are as follows:
   - LeanBalancer SPI: provides LoadBalancer to communicate with Invoker directly without Kafka in the middle (Invoker does not exist as a separate entity; it is built together with Controller)
   - LeanMessagingProvider SPI: provides Producer/Consumer implementers to communicate via in-memory queue instead of Kafka.
   - Ansible deployment: added controller-lean.yml and other files required for the Ansible deployment. Since lean controller is a combination of the controller + invoker projects, its ansible deploy.yml requires most of the values from both. Currently this problem is resolved by partially replicating variables from the regular invoker's deploy.yml to the tasks/invoker-lean.yml. Probably it would be better to avoid this duplication by having everything we need for lean in the regular deploy.yml. 
   - Dockerfile: to build Lean controller docker image, which is a merge of the regular invoker + controller Dockerfile
   - Vagrantfile: a small change to make Lean available using environment variable
   
   ## My changes affect the following components
   - [ ] API
   - [x] Controller
   - [ ] Message Bus (e.g., Kafka)
   - [x] Loadbalancer
   - [x] Invoker
   - [ ] Intrinsic actions (e.g., sequences, conductors)
   - [ ] Data stores (e.g., CouchDB)
   - [ ] Tests
   - [x] Deployment
   - [ ] CLI
   - [ ] General tooling
   - [x] Documentation
   
   ## Types of changes
   - [ ] Bug fix (generally a non-breaking change which closes an issue).
   - [x] Enhancement or new feature (adds new functionality).
   - [ ] Breaking change (a bug fix or enhancement which changes existing behavior).
   
   ## Checklist:
   
   - [x] I signed an [Apache CLA](https://github.com/apache/incubator-openwhisk/blob/master/CONTRIBUTING.md). 
   - [x] I reviewed the [style guides](https://github.com/apache/incubator-openwhisk/wiki/Contributing:-Git-guidelines#code-readiness) and followed the recommendations (Travis CI will check :).
   - [ ] I added tests to cover my changes.
   - [x] My changes require further changes to the documentation.
   - [x] I updated the documentation where necessary.
   

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