Add service.name to MDC

[cleverchuk]

Is your feature request related to a problem? Please describe.
Currently, trace_id, trace_flags and span_id are added to MDC, however the service.name is not. This attribute is needed as well to tie the logs to the service that generated the logs. The current solution only allows tying them to a trace.

Describe the solution you'd like
Add service.name to the MDC so that it can be accessible to loggers.

Describe alternatives you've considered
Accept logs via the OTLP. This assumes that the system speaks OTLP natively which is not the case.

Additional context
Ability to correlate logs exported via non-OTLP to service. The logs are exported by reading the log file.

[mateuszrzeszutek]

This is something that is currently (sort of) available in the Splunk distro -- it's done in a bit hacky way, where we copy resource attributes over to system properties: https://github.com/signalfx/splunk-otel-java/blob/main/custom/src/main/java/com/splunk/opentelemetry/resource/ResourceAttributesToSystemProperties.java

@open-telemetry/java-instrumentation-maintainers we wouldn't mind upstreaming feature over to this repo, if there's a broader interest here. (Of course, not as a sysprop hack: I believe if we were to do that we would add configuration setting for a list of resource attribute keys that are to be captured as part of MDC/ThreadContext)

[trask]

add configuration setting for a list of resource attribute keys that are to be captured as part of MDC/ThreadContext

sgtm 👍

[cleverchuk]

I'll like to take this one.

[cleverchuk]

@mateuszrzeszutek Where would be a good place to add this implementation? It looks like the implementation will need to be able to access the Resource object as seen by the user code.

[mateuszrzeszutek]

Where would be a good place to add this implementation?

To the MDC/ThreadContext modules, e.g. logback-mdc-1.0, log4j-context-data-2.7

It looks like the implementation will need to be able to access the Resource object as seen by the user code.

Yep -- I think we'll need to add a new bootstrap module that'll include a class holding the resource Attributes in a static var; initialized somewhere in the AgentInstaller. The logging modules could then get the configured attributes from the bootstrap class.

[cleverchuk]

@mateuszrzeszutek Struggling to find a way to access the Resource. This PR removed a clean way to access it. It seems like an option might be to make a resource customizer and add it here. However that looks like it's meant to be a user interface only and the attributes cached at that point won't contain any user customization. How should I proceed?

[laurit]

@cleverchuk In javaagent-tooling create a class called SdkAutoconfigureAccess in io.opentelemetry.sdk.autoconfigure.

package io.opentelemetry.sdk.autoconfigure;

import io.opentelemetry.sdk.resources.Resource;

public final class SdkAutoconfigureAccess {

  public static Resource getResource(AutoConfiguredOpenTelemetrySdk sdk) {
    return sdk.getResource();
  }

  private SdkAutoconfigureAccess() {}
}

in AgentInstaller add something like

private static void setResourceAttributes(AutoConfiguredOpenTelemetrySdk autoConfiguredSdk) {
   Resource resource = SdkAutoconfigureAccess.getResource(autoConfiguredSdk);
   // add ResourceAttributesHolder to javaagent-bootstrap module. you'll probably have to convert Attributes -> Map<String, String> somewhere
   ResourceAttributesHolder.setAttributes(resource.getAttributes());
}

call this method in installBytebuddyAgent before calling BeforeAgentListeners (could be after also, just a general guideline to help you locate the correct place).
Now you have the attributes available in a class called ResourceAttributesHolder that is in boot loader and accessible from logger javaagent instrumentations. For library instrumentations you'll have to do this differently, but I think these can be ignored for now.

[cleverchuk]

@laurit @mateuszrzeszutek
Do I need write access or make use of a fork to push a branch/PR?

[cleverchuk]

It looks like it should be a fork

[cleverchuk]

@laurit please can you take a look at the draft PR at your convenience. How do I make the failing tests pass?