pg instrumentation records wrong db connection string

[davazp]

What version of OpenTelemetry are you using?

"@opentelemetry/auto-instrumentations-node": 0.26.1

What version of Node are you using?

v16.13.0

What did you do?

The pg instrumentation records the connection string as localhost on pg-pool.connect even when that is not the right value. The problem is here:

opentelemetry-js-contrib/plugins/node/opentelemetry-instrumentation-pg/src/utils.ts

Lines 53 to 58 in 3d7a4d6

	export function getJDBCString(params: PgClientConnectionParams) {
	const host = params.host || 'localhost'; // postgres defaults to localhost
	const port = params.port || 5432; // postgres defaults to port 5432
	const database = params.database || '';
	return `jdbc:postgresql://${host}:${port}/${database}`;
	}

The logic in pg is of course more complex than that. In particular, it looks at the PGHOST environment variable that I am setting.

So pg connects to the right host, but it is recorded in the span as localhost.

This bug is not present in the .query spans because we look at the parameters of the pg client. Unfortunately, pg-pool doesn't know about how the parameters. They aren't resolved yet.

What did you expect to see?

pg-pool.connect should not show the wrong connection string.

What did you see instead?

localhost

Additional context

I don't think that replicating the same logic is sensitive here. Among other things, reading environment variables might have performance implications.

One conservative option is to not include the connection string if we don't have all the values, instead of defaulting to localhost (and same for the port 5432).

Other ideas? I can try to help with a PR.

[davazp]

It's easy to workaround this by defining host like host: process.env.PGHOST when defining the pg pool.

[dyladan]

This will likely be resolved by #781 when we change to use the connection string instead of a built jdbc string yes?

[davazp]

Will it? I can keep an eye on it. But I don't know how the span at pg-pool.connect will know the target of the client.

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