add Jaeger target

[lust4life]

• should resolved try add a target for jaeger tracing #379

it works:

[haf]

This is good code; I think it needs a test suite, too.

[haf]

This;

• needs unit/integration tests like the other targets
• needs to add docs into the readme
• needs to discuss, either in code, or here, how child spans are to be sent and,
• needs to discuss the limitations of the existing code and how it is to be extended

It would be nice to also document how to run a minikube or docker-compose with Jaeger; I'll then test it locally before releasing it.

[haf]

Nice! Do you think you could bump paket as well, and I'll make a new release tonight?

[haf]

Ping @lapponiandevil — this should interest you

[lust4life]

@haf away from laptop few days,

• add ut for jaeger target.
• add usage in readme

needs to discuss, either in code, or here, how child spans are to be sent

span are created from logger, and inherit IDisposable, have a finish method, user can use one of them(Dispose/finish) to trigger the log action (generate span info, use its logger to send them to targets).

before the span finish, every log message produced are belong to this span (if they are flow the execution context and using ambientSpanId middleware to set the parentSpanInfo or parentSpanId). And user can set them explicitly, if they cann't use the ambient info.

when target receive a log message (message without spanInfo context),

• it will be appended to buffer waiting for its span to finish. If it has no spanId context , it will be dropped, since jaeger target will only process span and its logs. (this can be filtered before sending to targets by config a pipeline)
• if its span message (message with spanInfo context) arrived, it will find its log messages and generate a jaeger span, if reach the target's conf BatchSpanSize, it will be sent to jaeger's agent through a udp client. if not, it will append to a buffer.
• the AutoFlushInterval in conf is used for a time control, when span is not reach the limit size and there is not any new span created.
• the RetentionTime in conf is used for a situation if user forget to finish its span, the log message generated will be gc after this RetentionTime. Avoid memory leaks.

[lust4life]

needs to discuss the limitations of the existing code and how it is to be extended

limitations:

• no sampler for now, every span will be sampled if they are received by the target.

  extend : need refactor SpanInfo, using something like spanContext , has a flags to indicate whether or not to sampled this span, and inherit this falg when creating a child span

• no support for Inject/Extract, need user do themselves if they want to chain their services's tracing as one.

  • https://github.com/jaegertracing/jaeger-client-go/blob/master/tracer.go#L304-L325
  • https://github.com/opentracing/specification/blob/master/specification.md#inject-a-spancontext-into-a-carrier

  extend: implements a b3-propagation ? or implements a adapter for https://github.com/opentracing/opentracing-csharp

[lust4life]

It would be nice to also document how to run a minikube or docker-compose with Jaeger; I'll then test it locally before releasing it.

• you can download the all-in-one binaries to test locally
  • https://www.jaegertracing.io/download/
• then run ./jaeger-all-in-one => dotnet run aspnetcore.csharp examples in logary repo :
  
• then browser http://localhost:16686/search