trace-context-w3c VS opentelemetry-specification

The answer is Context Propagation. The HTTP example is a classic and W3C even covers it. The propagation is adding the important fields from the context into the HTTP headers and having the other application extract those values and inject them into its trace context. This concept applies to any other way of communication. Here, we will focus on message brokers and how you can achieve context propagation for those.

I've been playing with OTEL for a while, with a few backends like Jaeger and Zipkin, and am trying to figure out a way to perform end to end timing measurements across a graph of services triggered by any of several events.

Consider this scenario: There is a collection of services that talk to one another, and not all use HTTP. Say agent A0 makes a connection to agent A1, this is observed by service S0 which triggers service S1 to make calls to S2 and S3, which propagate elsewhere and return answers.

If we limit the scope of this problem to services explicitly making HTTP calls to other services, we can easily use the Propagators API [1] and use X-B3 headers [2] to propagate the trace context (trace ID, span ID, parent span ID) across this graph, from the origin through to the destination and back. This allows me to query the metrics collector (Jaeger or Zipkin) using this trace ID, look at the timestamps originating at the various services and do a T_end - T_start to determine the overall time taken by one call for a round trip across all the related services.

However, this breaks when a subset of these functions cannot propagate the B3 trace IDs for various reasons (e.g., a service is watching a specific state and acts when the state changes). I've been looking into OTEL and other related non-OTEL ways to capture metrics, but it appears there's not much research into this area though it does not seem like a unique or new problem.

Has anyone here looked at this scenario, and have you had any luck with OTEL or other mechanisms to get results?

[1] https://opentelemetry.io/docs/specs/otel/context/api-propaga...

[2] https://github.com/openzipkin/b3-propagation

[3] https://www.w3.org/TR/trace-context/

-- https://www.w3.org/TR/trace-context/

For context propagation, why not just reuse the existing trace context that most frameworks and toolkits generate for http requests? I've had to apply some elbow grease to get it play nice but once it does you're able to use tools like Jeager, etc as part of your asynchronous flow as well.

(Note that OpenTelemetry uses, by default, the W3C context propagation specification, while Istio uses the B3 context propagation specification – this can be modified).

World Wide Web Consortium (W3C) has recommendations on the format of trace contexts. The aim is to develop a standardized format of passing trace context over standard protocols like HTTP. It saves a lot of time in distributed tracing implementation and ensures interoperability between various tracing tools.

The main objective is to propagate a message with traceparent id throw two APIs and one worker using W3C trace context standard. The first-api calls the second-api by a http call while the second-api has an asynchronous communication with the worker by a message broker (rabbitmq was chosen for that). Furthermore, zipkin was the trace system chosen (or vendor as the standard call it), being responsible for getting the application traces and building the distributed tracing diagram:

It means that the OpenTelemetry project provides not only a specification to define the contract between the applications, collectors, and telemetry databases, but also a set of APIs, SDKs, and tools like instrumentation libraries (for different languages), collectors, operators, etc. OpenTelemetry is open-source and vendor-agnostic, so the project is not tied to any specific vendor or cloud provider.

Sure, happy to provide more specifics!

Our main issue was the lack of a synchronous gauge. The officially supported asynchronous API of registering a callback function to report a gauge metric is very different from how we were doing things before, and would have required lots of refactoring of our code. Instead, we wrote a wrapper that exposes a synchronous-like API: https://gist.github.com/yolken-airplane/027867b753840f7d15d6....

It seems like this is a common feature request across many of the SDKs, and it's in the process of being fixed in some of them (https://github.com/open-telemetry/opentelemetry-specificatio...)? I'm not sure what the plans are for the golang SDK specifically.

Another, more minor issue, is the lack of support for "constant" attributes that are applied to all metrics. We use these to identify the app, among other use cases, so we added wrappers around the various "Add", "Record", "Observe", etc. calls that automatically add these. (It's totally possible that this is supported and I missed it, in which case please let me know!).

Overall, the SDK was generally well-written and well-documented, we just needed some extra work to make the interfaces more similar to the ones were were using before.

OpenTelemetry is an open-source collection of tools, APIs, and SDKs that aims to standardize the way we generate and collect telemetry data. It follows a specification-driven development. The OpenTelemetry specification  has design and implementation guidelines for how the instrumentation libraries should be implemented. In addition, it provides client libraries in all the major programming languages that follow the specification.

Two problems with OpenTelemetry:

1. It doesn't know what the hell it is. Is it a semantic standard? Is a protocol? It is a facade? What layer of abstraction does it provide? Answer: All of the above! All the things! All the layers!

2. No one from OpenTelemetry has actually tried instrumenting a library. And if they have, they haven't the first suggestion on how instrumenters should actually use metrics, traces, and logs. Do you write to all three? To one? I asked this question two years ago, not a single response. [1]

[1] https://github.com/open-telemetry/opentelemetry-specificatio...

OpenTelemetry Specification GitHub

One update to this: we proposed replacing the count suffix in OpenTelemetry with total to match Prometheus/OpenMetrics. That discussion resulted in the count suffix being removed from the OpenTelemetry semantic conventions. We'll soon update our metric from being called function.calls.count to just function.calls and the generated Prometheus queries will refer to function_calls_total. That resolves one of the main conflicts between the two specs.

This is your best bet if you want to track status updates: https://github.com/open-telemetry/opentelemetry-specification/issues/2911

OpenTelemetry is a standard for implementing telemetry in your applications. It provides a specification, containing the requirements that all implementations should follow as well as some implementations for major languages, including an API and a SDK to interact with it.

At this point, we are about to do the real work where we have to configure OpenTelemetry and export telemetry data to New Relic. Exporting this kind of data relies on a specific protocol; the OpenTelemetry Protocol or OTLP.

OpenTelemetry provides instrumentation libraries for your application. The development of these libraries is guided by the OpenTelemetry specification. The OpenTelemetry specification describes the cross-language requirements and design expectations for all OpenTelemetry implementations in various programming languages.