Added tracing support

[ResuBaka]

Related issues

closes #3506

Short description and why it's useful

This adds support to load a tracing library at the start of the app.

I have added an example for google cloud tracing.

You would use it like this.
src/trace/index.js

module.exports.default = () => {
require('./googleCloud')
}

Screenshots of visual changes before/after (if there are any)

Which environment this relates to

Check your case. In case of any doubts please read about Release Cycle

• Test version (https://test.storefrontcloud.io) - this is a new feature or improvement for Vue Storefront. I've created branch from develop branch and want to merge it back to develop
• RC version (https://next.storefrontcloud.io) - this is a stabilisation fix for Release Candidate of Vue Storefront. I've created branch from release branch and want to merge it back to release
• Stable version (https://demo.storefrontcloud.io) - this is an important fix for current stable version. I've created branch from hotfix or master branch and want to merge it back to hotfix

Upgrade Notes and Changelog

• No upgrade steps required (100% backward compatibility and no breaking changes)
• I've updated the Upgrade notes and Changelog on how to port existing VS sites with this new feature

IMPORTANT NOTICE - Remember to update CHANGELOG.md with description of your change

Contribution and currently important rules acceptance

• I read and followed contribution rules
• I read the TypeScript Action Plan and adjusted my PR according to it
• I read about Vue Storefront Modules and I am aware that every new feature should be a module

[pkarw]

That’s really clever idea! Thanks!

[pkarw]

@ResuBaka could you please check the failing CI?

[ResuBaka]

It looks like not a problem from my changes.

https://travis-ci.org/DivanteLtd/vue-storefront/builds/582552893?utm_source=github_status&utm_medium=notification

Should I still fix it or should some one else fix it?

[patzick]

Sorry for tests, was my fault with merge, fixed:)

Although, don't you think it would be better to add this as a new module which can be included in the project, not by config, just by registering it? In develop we have rewritten modules system, @filrak could you take a look? :)

[pkarw]

I belive the problem is that modules can’t extend server.js @filrak this is pretty interesting case

Maybe we can just add a hook in core/server.js that can be bound from within the module just before first request is being handled?

@filrak maybe you could take care of this one by this chance:
#2494

[pkarw]

If not extending the modules for server app extensions then this way @ResuBaka proposed is the only way; the only thing is that’s gerrnarijg dependency from core to src but at this stage we do have these dependencies anyway so it’s fine with me

[pkarw]

Another idea is to add traces from the src/server - https://github.com/DivanteLtd/vue-storefront/blob/master/src/server/index.js - which won’t require us to modify core/server; these extensions are being registered only serverside

[ResuBaka]

I fist had that Idea too but all tracing stuff should happen as early as it gets. So they trace every thing the right way.

So with my implementation you can add all tracing frameworks which can be implemented this way be called directly before all other code gets loaded.

[patzick]

@ResuBaka so let's wait for #3518 to be finished and then let's make first server module with your change, how does it sound for you? :)

[ResuBaka]

I would use the server module but mine needs to be done before express is started/created so it would still be the best to have it like I have done.

Here you have some info. All of them are telling the user to start it as the first module.
https://docs.datadoghq.com/tracing/setup/nodejs/

https://www.elastic.co/guide/en/apm/agent/nodejs/current/express.html

https://www.npmjs.com/package/@google-cloud/trace-agent

[filrak]

@ResuBaka interesting case, I will move extension point to the beginning

[pkarw]

@filrak so please just sync with @ResuBaka and let's have this ready to merge this week

[pkarw]

@ResuBaka @filrak - how about this one? Are we merging it in?

[ResuBaka]

I would say yes when we don't need typescript support for it or is that done in an other PR? @pkarw

[pkarw]

OK, I've merged it in

[filrak]

@pkarw
;(