HOSTNAME is blank when not present in environment

[nlindley]

What happened?

Steps to Reproduce

Ensure HOSTNAME is not present on process.env

Expected Result

HOSTNAME falls back to os.hostname()

Actual Result

HOSTNAME is blank

Additional Details

It looks like the intention is to use os.hostname() as the default for HOSTNAME in getEnv(), but then it’s getting replaced by the default values from DEFAULT_ENVIRONMENT. I think the order of { HOSTNAME: os.hostname(), } and DEFAULT_ENVIRONMENT could be swapped.

opentelemetry-js/packages/opentelemetry-core/src/platform/node/environment.ts

Lines 30 to 36 in ae0a3c5

	return Object.assign(
	{
	HOSTNAME: os.hostname(),
	},
	DEFAULT_ENVIRONMENT,
	processEnv
	);

OpenTelemetry Setup Code

No response

package.json

No response

Relevant log output

No response

[pichlermarc]

Hi @nlindley thanks for reporting this. Looks like I mistakenly categorized this is a report for the EnvDetector resource detector, but there the results for that one seem correct. Also HostDetector returns the expected value. This is a report that concerns just getEnv(), correct?

If yes, then I think we'll do the following:

• remove the broken os.hostname() fallback as it's not doing anything
• keep the empty string as default
  • it's the parsing from the environment and if it is not set there, I think we should not apply any magic to it. While we don't use the HOSTNAME env var in our repo, other users might, and the might rely on that default being the empty string.