[FrontendProxy] Add tracing to Envoy

[julianocosta89]

Changes

As Envoy supports OpenTelemetry, I believe it would be great if we could use it.
https://www.envoyproxy.io/docs/envoy/latest/start/sandboxes/opentelemetry

This PR adds the configuration required to add tracing to Envoy.

Merge Requirements

For new features contributions please make sure you have completed the following
essential items:

• CHANGELOG.md updated to document new feature additions
• Appropriate documentation updates in the docs folder

Maintainers will not merge until the above have been completed. If you're unsure
which docs need to be changed ping the
@open-telemetry/demo-approvers.

[cartersocha]

We should add envoy to the current services architecture doc. Especially if there's a span coming from it

Should we add a simple envoy service doc with config instructions too?

[julianocosta89]

@cartersocha Not sure what exactly to write, but I've added the "how to" make Envoy produce spans.

[cartersocha]

I'm seeing errors on the frontend and checkout service

[cartersocha]

Not sure why the shipping service is throwing issues.

"13 INTERNAL: shipping quote failure: failed to get shipping quote: rpc error: code = Unknown desc = error sending request for url (http://quoteservice:8090/getquote): error trying to connect: dns error: failed to lookup address information: Name does not resolve"

[cartersocha]

A system prune cleared up the errors but I'm not seeing an envoy span in any trace. I see envoy as an orphan span currently and the main trace doesn't have it present

[julianocosta89]

@cartersocha true!
Something that I forgot to mention is that this is generating spans only when you navigate to the OTel-Demo page.
The loadgen doesn't send requests through the envoy, but to the frontend container directly.

[cartersocha]

I see! lgtm.

This is where it would be nice to have non synthetic requests set the attribute to filter on.

[cartersocha]

Please add a note in the envoy services doc at the top saying only non synthetic requests will trigger the envoy tracing.

Lgtm otherwise

[puckpuck]

One small nit. everything works as expected. 👍