Replay manual start doesn't trigger recording

[earlAchromatic]

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which package are you using?

@sentry/vue

SDK Version

7.25

Framework Version

Vue 2.7.14

Link to Sentry event

No response

Steps to Reproduce

Initialize Sentry without Replay following the Replay docs:

Sentry.init({
 dsn: config.sentryDsn
 replaysOnErrorSampleRate: 1.0,
 integrations: [],
})

// initialize Replay outside of integrations

const replay = new Sentry.Replay()

replay.start() // no recording triggered on error

Expected Result

Expected recording to be triggered on error and show up in the UI. This doesn't happen.

Actual Result

No recording is sent to UI. This is because _setup is not called when Replay is initialized outside of the integrations array. _setup is responsible for initializing a ReplayContainer instance which is required to actually start a recording. The result is when Replay.start is called and Replay has been initialized outside of the Sentry config, no recording every takes place. I am able to manually start recording by doing this though:

const replay = new Sentry.Replay()

replay.setupOnce() // this method must be called to manually set up before starting.
replay.start()

I do not believe this the intended behavior. Or maybe this is intentional and the docs just need updated?

It looks like this could be fixed by calling setupOnce inside of Replay.start when it is called if a _setupComplete flag has not been previously set.

[Lms24]

Hi @earlAchromatic thanks for reporting this! This might have been an oversight while working on #6407 and subsequent refactorings. We'll look into this. For now, the workaround is to specify Replay in the integrations array of Sentry.init.

Just out of curiosity: Why are you trying to initialize Replay manually?

[billyvg]

FWIW we hit the same bug in Sentry SaaS, but we have a unique case since we are controlling SDK sampling from an external source (flagr), where feature flags are not available when calling Sentry.init.

[earlAchromatic]

Just out of curiosity: Why are you trying to initialize Replay manually?

@Lms24 Our use case is dynamically initializing Replay based on a limited set of users that have opted in, in order to evaluate Replay. We have also talked about possibly using manual start/stop in order to scope inbound replays to specific features (think intersection observer or mouseenter events for instance) but that would be down the road. Thanks for giving it a look.

[mydea]

This can now be achieved with the new addIntegration API (added in 7.30):

Sentry.init({
 // not added yet
 integrations: []
});

// sometime later:
Sentry.getCurrentHub().getClient().addIntegration(new Sentry.Replay());

This will properly register the integration & start the replay.

Feel free to reopen this if that doesn't work as expected for you!

[brotherko]

@mydea My idea is to sample 100% for certain users. But then only track the rest of the users on error. Given the sampling rate is set up in Sentry's top-level configuration, how to set this up?

[mydea]

You could achieve this with something like this:

1. Do not add replay integration in Sentry.init()
2. At the point in time where you do know that you want to setup replay (e.g. you know the user), do:

const client = getCurrentHub().getClient()!;
const options = client.getOptions();
options.replaysSessionSampleRate = 0; // or 1
options.replaysOnErrorSampleRate = 1; // or 0;

client.addIntegration(new Replay()); // <-- this will trigger start

Note that depending on when you call this, you may loose a portion of the replay (=stuff that happened before this).

Note that we do not recommend to do this - ideally, you know at Sentry.init() time how you want to sample this session, as that's the only way to ensure we can capture the whole session correctly.