faas-pipeline

Complex OpenFaaS function composition

faas-pipeline offers executing of complex pipelines on top of OpenFaaS. It does this by:

• Defining its own pipeline definition language
• Defining its own protocol for data exchange between functions
• Accepting pipeline definitions together with initial payload

faas-pipeline can:

• Process payloads concurrently. This is called ~split. The result of ~split operation is an array of results of all functions that were executed concurrently.
• Process payloads sequentially. This is called ~pipe. ~pipe operation results in a new payload based on its received payload.
• Include optional parameters, beside payload, when invoking each function.
• Send custom metrics for each invoked function to FaaS' built-in Prometheus.

These can be combined in any number of ways. For example:

pipeline:
	~pipe:
		- ~split: # sends the received payload into fn1, fn2 and fn3
			fn1:
			fn2:
			fn3:
		- some-merging-fn: # this function acts on array of results from fn1, fn2 and fn3 with parameters of whatever1 and whatever2
			some-param: whatever1
			another-param: whatever2

Each compatible function must:

• Expect to receive JSON with optional payload and params properties.
• Return JSON with either error or result property and optional metrics property.

Execution stops on first error or when the entire pipeline has ran. Pipeline run thus either results in a free-form result or in a free-form error.