otel tracing propagation in wrp

[schmidtw]

To support OpenTelemetry to the CPE, we need to add the propagation to the WRP messages & we have a few options.

References:

• B3
• W3C Trace Context

Option 1 - Add to headers

Add the B3 or W3C headers to the WRP headers. It would look a bit like this:

B3

wrp_req_msg {
    .trans_id      = 'c07ee5e1-70be-444c-a156-097c767ad8aa'
    .source        = 'source-address'
    .dest          = 'dest-address'
    .partner_ids   = 'Partner 1, Partner 2, Example'
    .content_type  = 'application/json'
    .headers       = [
        'X-B3: 80f198ee56343ba864fe8b2a57d3eff7-e457b5a2e4d86bd1-1-05e3ac9a4f6e3b90'
    ]
    .accept        = 'json'
    .payload (len) = 3
    .metadata      = {
        .n1: 'v1'
    }
}

W3C

wrp_req_msg {
    .trans_id      = 'c07ee5e1-70be-444c-a156-097c767ad8aa'
    .source        = 'source-address'
    .dest          = 'dest-address'
    .partner_ids   = 'Partner 1, Partner 2, Example'
    .content_type  = 'application/json'
    .headers       = [
        'traceparent: 00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01',
        'tracestate: congo=t61rcWkgMzE'
    ]
    .accept        = 'json'
    .payload (len) = 3
    .metadata      = {
        .n1: 'v1'
    }
}

With this approach no changes are needed to WRP & if you really wanted to you could even send down both at once.

The costs are the various WRP libraries won't help you much, but you do get access to your data.

Option 2 - Add to structure

wrp_req_msg {
    .trans_id      = 'c07ee5e1-70be-444c-a156-097c767ad8aa'
    .source        = 'source-address'
    .dest          = 'dest-address'
    .partner_ids   = 'Partner 1, Partner 2, Example'
    .content_type  = 'application/json'
    .tracing       = {
        .b3 = '80f198ee56343ba864fe8b2a57d3eff7-e457b5a2e4d86bd1-1-05e3ac9a4f6e3b90'
        .traceparent = '00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01'
        .tracestate = 'congo=t61rcWkgMzE'
    }
    .accept        = 'json'
    .payload (len) = 3
    .metadata      = {
        .n1: 'v1'
    }
}

The structure could also be flattened, but it's nice to see these are associated with tracing.

Commentary

Originally I was in favor of Option 2, but I'm more in favor of Option 1 since it's pretty simple, WRP largely doesn't care (the tracing will end up being sent in a separate message), and it makes use of the header field that has yet to have a good reason to exist.

While the consumer needs to deal with http style headers ... that seems like a fine trade-off to me.

Thoughts?

[schmidtw]

We're (Xmidt, RDK) going forward with Option 1.