Initial prototype

[erwinvaneyk]

This PR contains the first prototype (as demonstrated/discussed last Friday), with the following notable features:

• Core components implemented:
  • API (Server): both internal and external (gRPC and JSON) API.
  • Event Store (using NATS streaming) : Stores events, only actual stateful component.
  • Projector : constructing state from events.
  • Controller : manages workflow invocations
  • Scheduler : makes decisions based on the current state of a workflow invocation.
  • Fission Proxy : a separate server that ensures that the workflow engine conforms to the environment/function interface of Fission.
  • Parser: parses workflows into workflows that can be executed (e.g. resolves function names to uids)
• Initial data format for workflows, which supports declaration of tasks with dependency
• A hacked together, deployable binary under ./cmd/workflow-engine/
• Build and deploy (to kubernetes) scripts in ./build/
• Working example of a simple (sequential) workflow. To run:
  1. build & deploy fission which supports fission-workflow (currently there is a quick and dirty integration available: https://github.com/erwinvaneyk/fission/tree/fission-workflow-integration)
  2. Deploy fission-nats.yaml (currently the only 'additional' dependency of Fission-workflow
  3. build & deploy fission-workflow
  4. run ./examples/simple/deploy.sh which deploys functions and workflows
  5. invoke one of the workflows just like you would invoke a Fission function. For example, to request advice from the Fortunewhale: curl $FISSION_ROUTER/fission-function/fortunewhale
• Some (outdated) documentation is available under ./Docs/

Fyi @soamvasani