Must parse rendered template for hardware address validation

[gauravgahlot]

Description

The template rendering logic does not validate if the rendered template has the correct worker address or not. The workflow create request only fails while inserting the workflow details into the database. For example, if we have the following template:

version: "0.1"
name: hello_world_workflow
global_timeout: 600
tasks:
  - name: "hello world"
    worker: "{{.device_1}}"
    actions:
    - name: "hello_world"
      image: hello-world
      timeout: 60

Now, if we create a workflow with incorrect hardware details an error is returned from database:

$ tink workflow create -t e80169ae-4b35-11eb-bef7-0242ac120004 -r '{"invalid_device": "08:00:27:00:00:01"}'
// 2020/12/31 07:01:37 rpc error: code = Unknown desc = failed to create workflow: unable to insert into action list: invalid worker address:

Why is this needed

The validation of the worker/hardware address must happen before making any database call.

$ tink workflow create -t cb826ef8-4b61-11eb-ab9f-0242ac120004 -r '{"invalid_device": "08:00:27:00:00:01"}'
2020/12/31 12:15:37 rpc error: code = Unknown desc = failed to render template, invalid hardware address: {"invalid_device": "08:00:27:00:00:01"}

$ tink workflow create -t cb826ef8-4b61-11eb-ab9f-0242ac120004 -r '{"device_1": "08:00:27:00:00:01"}'
Created Workflow:  ecabf4ce-4b61-11eb-ab9f-0242ac120004

How Has This Been Tested?

• Unit tests
• Manually over vagrant setup

Checklist:

I have:

• updated the documentation and/or roadmap (if required)
• added unit or e2e tests
• provided instructions on how to upgrade

[codecov]

Codecov Report

Merging #408 (220e99d) into master (d7856c9) will increase coverage by 0.13%.
The diff coverage is 52.17%.

@@            Coverage Diff             @@
##           master     #408      +/-   ##
==========================================
+ Coverage   21.24%   21.38%   +0.13%     
==========================================
  Files          24       24              
  Lines        2170     2170              
==========================================
+ Hits          461      464       +3     
+ Misses       1667     1664       -3     
  Partials       42       42              

Impacted Files	Coverage Δ
grpc-server/workflow.go	28.80% <50.00%> (-0.76%)	⬇️
workflow/template_validator.go	80.59% <52.63%> (-11.07%)	⬇️

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