Support multiple ignored prefixes for code-level metrics

[rittneje]

By default code-level metrics will ignore callers with a prefix of github.com/newrelic/go-agent. You can customize this via IgnoredPrefix in the Config struct, but since it is not a list you cannot have it ignore both prefixes.

Either IgnoredPrefix should be deprecated and replaced with a list property, or it should be defined as a comma-separated list of prefixes. newrelic.ConfigCodeLevelMetricsIgnoredPrefix will be similarly impacted.

[nr-swilloughby]

Thanks for the feature enhancement suggestion. We'll look into that as soon as we can.

[nr-swilloughby]

I think the best approach here would be to replace IgnoredPrefix with a list property and change ConfigCodeLevelMetricsIgnoredPrefix to take a list of strings, preserving its call semantics to be backward compatible (since it can still be called with a single string argument like before).

[nr-swilloughby]

Oh, and this also similarly impacts the WithIgnoredPrefix option.

[rittneje]

@nr-swilloughby Since IgnoredPrefix is a public field of Config, you cannot replace it without breaking backwards compatibility. You would need two separate fields.

[nr-swilloughby]

@rittneje Yes, that's what I did. IgnoredPrefix will be a deprecated field (but still used if set), and the new one is IgnoredPrefixes is a slice of strings. ConfigCodeLevelMetricsIgnoredPrefix and WithIgnoredPrefix can be changed to take a variadic list of strings and still preserve the previous calling syntax, which is backwards compatible unless for some reason someone defines an interface type around those functions, but with those specific functions that seems very unlikely to happen.