Support resource detection when using the java agent

[dashpole]

From #247 (comment):

It seems that my current configuration is not enough to use the Google Cloud official Resource Detectors. Unlike Auto-Configuration for OpenTelemetry in Google Cloud, Resource Detectors are not designed as extension for javaagent, so I cannot enable them via otel.javaagent.extensions system property.

[dashpole]

This might need to happen after #266

[psx95]

Regarding #247 (comment)

As a trial, I enabled the Auto-Configuration for OpenTelemetry in Google Cloud as a javaagent extension, and it worked but metrics had no instance ID nor service ID in their attributes yet: generic_node{location:global,node_id:localhost,namespace:}

I did some investigation into this and here are my findings -

Summary

• Java Agent + Auto Exporter Setup works and I was able to view traces and metrics.
  • Note 1: Shaded version of auto-exporter is needed when using it as an extension to Java Agent.
  • Note 2: Service name was not appearing as a metric label (instance_id was being shown on GCE though), but was being shown in trace attribute. This might be a bug which needs to be addressed.
• Google Cloud Resource Detectors are now bundled into the Java Agent as of v2.2.0 Release. Instructions to enable this can be found on opentelemetry.io.
  • Note: To export telemetry to Google Cloud, you would still need to use the Auto-exporter as an extension to the agent, regardless of enabling the gcp-resource-detector built-in to the agent.
• For Java Agents v1.x.x, the resource detectors are not packaged in the Agent, however exporting to Google Cloud via the Agent still works when using the shaded auto-exporter since auto-exporter has the resource detectors built-in.

Is this in-line with your findings @KengoTODA ?

@dashpole As part of this issue, I will look into why service name is not appearing in the metric attributes when using Java Agent.

[dashpole]

@psx95 I consider this issue fixed. You are welcome to track the service.name attribute issue here, or in a new issue.

[psx95]

Created #313 to track this. Will mark this issue as completed.