Add sampleRate config option

[LewisJEllis]

Basically the same thing as getsentry/sentry-javascript#885

/cc @benvinegar @dcramer

[benvinegar]

Needs test.

[LewisJEllis]

Added tests. Feels kinda messy compared to the raven-js parallels with the nice sinon setup :/

[benvinegar]

🍗

[MarkHerhold]

Sorry for the dumb question, but what is the use case for this?

[benvinegar]

@MarkHerhold – This is analogous to rate-limiting, except the rate-limiting occurs on the client, not the server. This has the upside of sending less traffic to sentry.io ($) / your own Sentry server at the expense of losing data.

Sampling is often necessary for very high traffic applications.

[MarkHerhold]

Ah, so this would be for applications that are utilizing Sentry more like a logging service rather than an error tracker?

[benvinegar]

It's more like – if you have 1 million active users, and they all hit the same error, do you really need 1 million error reports to be sent? Probably not.

So, if you have an app with a really huge active user count, you can probably safely suppress a fraction of error reports using sampleRate to save bandwidth, $, etc. This is 100% at the discretion of the application author; it is not enabled by default.

[MarkHerhold]

Got it, thanks!