Server-Sent Events support - closes #2830

[benfrancis]

No description provided.

[benfrancis]

Work-in-progress Server-Sent Events implementation for W3C WoT compliance (#2830), which is currently blocking #2806.

This still needs tests. It's a bit tricky to test manually because Postman doesn't support Server-Sent events, but you can use curl to see the raw output of the event stream.

Note that JavaScript Consumers using EventSource you will need to provide a JWT in a query string (as is currently the case with WebSockets), because the EventSource API doesn't allow sending an Authorization header. I've used the same approach in the example curl command below, you just need to insert your own JWT.

curl http://localhost:8080/things/virtual-things-10/events/virtualEvent?jwt={jwt} -H 'Accept: text/event-stream'

For testing you can use the Virtual Actions & Events Thing from the Virtual Things add-on, which emits an event when you invoke the "no input" action.

[codecov-commenter]

Codecov Report

Merging #2863 (5bacefc) into master (f68be20) will increase coverage by 0.13%.
The diff coverage is 86.84%.

❗ Current head 5bacefc differs from pull request most recent head a52a63b. Consider uploading reports for the commit a52a63b to get more accurate results

@@            Coverage Diff             @@
##           master    #2863      +/-   ##
==========================================
+ Coverage   65.25%   65.39%   +0.13%     
==========================================
  Files         124      124              
  Lines        7952     7987      +35     
  Branches     1328     1332       +4     
==========================================
+ Hits         5189     5223      +34     
- Misses       2720     2721       +1     
  Partials       43       43              

Impacted Files	Coverage Δ
src/router.ts	98.94% <ø> (ø)
src/controllers/events_controller.ts	89.58% <86.48%> (-10.42%)	⬇️
src/models/thing.ts	69.20% <100.00%> (+0.11%)	⬆️
src/controllers/internal_logs_controller.ts	84.21% <0.00%> (-1.76%)	⬇️
src/app.ts	56.32% <0.00%> (+2.87%)	⬆️

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[benfrancis]

OK, I've added integration tests. This is now ready for review.

[benfrancis]

@relu91 I'd be interested in your review here too if you get chance.

[relu91]

The PR looks good, aside from some comments below I'd refactor the unit test provided in smaller tests. I understand that logically they all belong to the same category (sse tests) but if we want to group them logically we can just use the describe function:

describe("Server Sent Event testing", () => {
  it("should subscribe", ()=>{})
  it("should subscribe to multiple events", ()=>{})
  it("should fail for not existing events", ()=>{})
}); 

What do you think?

[benfrancis]

Thanks for the review @relu91, great feedback. I think I've addressed all your comments.

[relu91]

Perfect 👍🏻

[benfrancis]

@tim-hellhake agreed to make @relu91 a peer of the gateway module, so landing based on @relu91's review.

@tim-hellhake comments still welcome if you want to review.