Access patterns to config in instrumentations

[blumamir]

Now that https://github.com/open-telemetry/opentelemetry-js/pull/4659 will soon merge, all instrumentations can apply cleanups to how the config object is consumed.

There are now 2 options:

1. using this._config from InstrumentationAbstract which is now typed correctly.
2. using the getConfig() function from the Instrumentation interface.

I think we should decide which one is superior and refactor all existing instrumentations to use a consistent pattern. I tend to prefer the getConfig option as the getter can potentially be overridden with custom logic which will be lost if we simply access the _config property.

If we choose option (2), should we make the _config object private instead of protected?

Would love to hear more opinions.

[blumamir]

Pros options 1:

• shorter to write
• bit more performant (I think)

Pros options 2:

• will work correctly for advanced cases if the function is overridden
• can make _config private to decrease API surface.
• aligns will with tracer, meter and logger class properties, which are private and are only accessed via a getter.

[david-luna]

Here is my opinion. If we already have a public API to access the field I think we should leverage that for accessing even in subclasses. Also I'm not sure about the significance the perf gain of having direct access to the config which is the most appealing pro of option 1.

[pichlermarc]

Here is my opinion. If we already have a public API to access the field I think we should leverage that for accessing even in subclasses. Also I'm not sure about the significance the perf gain of having direct access to the config which is the most appealing pro of option 1.

I agree. IMO we should go with getConfig() and make _config private.

[blumamir]

Implemented in https://github.com/open-telemetry/opentelemetry-js-contrib/pull/2289 Would appreciate any review on this PR 🙏