Disable service links to prevent environment variable conflict

[mikelorant]

It is common to name the Jaeger agent service jaeger-agent. This forces Kubernetes to create an environment variable JAEGER_AGENT_PORT as part of the service links. This conflicts with the an internal environmental variable used in the client library.

https://github.com/jaegertracing/jaeger-client-go/blob/704ce2849e9abb8af82edb2a3375e9e163092427/config/config_env.go#L51

This will cause the query UI to crash with the following error:

{"level":"fatal","ts":1597712251.5144613,"caller":"command-line-arguments/main.go:76","msg":"Failed to read tracer configuration","error":"cannot obtain reporter config from env: cannot parse env var JAEGER_AGENT_PORT=udp://100.69.94.248:5775: strconv.ParseInt: parsing \"udp://100.69.94.248:5775\": invalid syntax" ...

If this variable is set it is meant to be 6831 but Kubernetes sets it to the first port listed in the service for the agent. Jaeger query UI does not expect this value.

Service links can be disabled as part of the pod specification.

If the service environment variables are not desired (because possible clashing with expected program ones, too many variables to process, only using DNS, etc) you can disable this mode by setting the enableServiceLinks flag to false on the pod spec.

See also: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.18/#pod-v1-core

By automatically setting enableServiceLinks to false this edge case will no longer occur.

This should be added to all deployment specifications created by the operator.

[mikelorant]

This improvement would fix the following open issue:
jaegertracing/jaeger#1986

[jpkrohling]

By automatically setting enableServiceLinks to false this edge case will no longer occur.

TIL! Thank you for this information. Would you be open to sending a PR with this change?

[mikelorant]

I don't know much about writing Go but I decided to give it a shot. The unit tests are the main challenge for me so it is likely I have made mistakes there. Getting some assistance from my work to verify the code works correctly before I put up a proper pull request but you can see my changes:

master...fairfaxmedia:master

[jpkrohling]

I left a couple of comments there. You are certainly on track!

[mikelorant]

Have someone from work helping solving the issues now. Hopefully have this done soon :)

[mikelorant]

Want to thank @dackroyd for sorting out all the mistakes I made and assisting with resolving the issues you mentioned.

[mikelorant]

We have an image and will deploy it tomorrow. Are you able to confirm the spec changes required in the operator to set a custom query image?

[jpkrohling]

Looks very good now! Once you confirm that it works as intended, do send a PR with that change. Not sure what you mean with your question though.

[mikelorant]

Have just had confirmation that the unit tests pass.