Add ability to set multiple tags at the same time

Today we have a setTag(key, value) function which allows you to set a tag on the current transaction.

As discussed on the APM forum, it would be nice to be able to set more than one tag at a time.

Since the existing setTag is singular, I’m thinking it’s better to create a new function. We can keep supporting both functions or we can deprecate the old one. I’m not sure what’s best.

Proposed new API:

agent.setTags({key1: 'value', key2: 'value'})

Questions:

• Should we deprecate setTag or keep supporting it?
• Should it be possible to clear the already set tags, or will calling setTags multiple times just add to the list of tags?

[AdriVanHoudt]

The object + set implies full overwrite instead of merge to me

[watson]

@Qard I think with for instance addTags() we’ll not want to do anything if there isn’t currently an active transaction. It could be that instrumentation have been disabled, or we’re sampling and this current request hasn’t been chosen as a sample, or simply that there’s a bug where we have lost context due to an un-patched async operation. We have have the same issue with agent.buildSpan() btw, this will return null instead of a span if there isn’t an active transaction so all subsequent calls to span.* needs to have a guard before it. So it would be cool if we could find a solution to this that made the API simpler to work with 😃