support jaeger.tags when calling 'GetSamplingStrategy', e.g. return R…

[limfriend]

…ATE_LIMITING when jaeger.tags = {region,CA}

Signed-off-by: osfriend [email protected]

Which problem is this PR solving?

SamplingStrategy support for agent level tag
e.g. return RATE_LIMITING when jaeger.tags = {"region","CA"}

Short description of the changes

transparent metadata which converted from 'jaeger.tags' to collector service

[limfriend]

@pavolloffay @jpkrohling could you help to review this PR, I have not idea about CI build failure.

[yurishkuro]

Could you please first open a ticket and describe the business use case that you're trying to solve?

[limfriend]

@yurishkuro add issue for this PR, #1692

[yurishkuro]

Thanks. So it looks like this PR only passes the agent tags as metadata to the collector, it does not actually implement being able to vary sampling strategies in response to those tags.

[limfriend]

your are right, It is easy to write code for passing tags to collector . but It is complex to get sampling strategies for composing serviceName and agentTag.

• Maybe some agent tags is global for sampling strategies. e.g samplingRate=1 when t 'environment' tag= test.
• maybe some serviceName is ignore agent tags for sampling strategies. e.g ‘order’ service is always samplingRate=1， No matter what the 'environment' tag is test or product.

I have no clean idea about how to config the priority for serviceName and agentTag. Could you please give me some help?

[yurishkuro]

There is a related proposal here #365 (comment), which will require representing sampling rules with more granularity than just service-operation as today. That approach is easily generalizable to include agent tags.

[limfriend]

yes, it is a good generalizable proposal. When is it probably done? could you please merge the agent code first, then I extended agentTag Sampling base this sampling rules.

[yurishkuro]

I don't know if @lookfwd made any progress on it. We internally have similar requirements and will likely work on that functionality in September. But we haven't finalized the backend design yet.

I don't want to merge this PR until we have a design for the backend, because it's not guaranteed that we will want to keep the data path in this form. We can keep it open for now.

[jpkrohling]

What's the status of this PR?