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re-use live mode config - and improve docs on how to start liveMode (#1003)

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* Use config.liveMode to turn on liveMode in the timer

* Discussion of `startLive(1500)` was incorrect as startLive is based on timestamps, not playback offsets.  Also reorder to introduce `addEvent` earlier

Co-authored-by: Eoghan Murray <eoghan@getthere.ie>
This commit is contained in:
Justin Halsall
2026-04-01 12:00:00 +08:00
committed by GitHub
parent 268229b8b3
commit b9516a2759
3 changed files with 28 additions and 13 deletions
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25
docs/recipes/live-mode.md
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@@ -5,23 +5,28 @@ If you want to replay the events in a real-time way, you can use the live mode A
When you are using rrweb's Replayer to do a real-time replay, you need to configure `liveMode: true` and call the `startLive` API to enable the live mode.
```js
const replayer = new rrweb.Replayer([], {
const ANY_OLD_EVENTS = [];
const replayer = new rrweb.Replayer(ANY_OLD_EVENTS, {
liveMode: true,
});
replayer.startLive(FIRST_EVENT.timestamp - BUFFER);
replayer.startLive();
```
When calling the `startLive` API, there is an optional parameter to set the baseline time. This is quite useful when you live scenario needs a buffer time.
Later when you receive new events (e.g. over websockets), you can add them using:
For example, you have an event recorded at timestamp 1500. Calling `startLive(1500)` will set the baseline time to 1500 and all the timing calculation will be based on this.
```
function onReceive(event) {
replayer.addEvent(event);
}
```
But this may cause your replay to look laggy. Because data transportation needs time(such as the delay of the network). And some events have been throttled(such as mouse movements) which has a delay by default.
When calling the `startLive` API, there is an optional parameter to set the baseline time. By default, this is `Date.now()` so that events are applied as soon as they come in, however this may cause your replay to look laggy. Because data transportation needs time(such as the delay of the network). And some events have been throttled(such as mouse movements) which has a delay by default.
So we can configure a smaller baseline time to the `startLive` API, like `startLive(500)`. This will let the replay always delay 1 second than the source. If the time of data transportation is not longer than 1 second, the user will not feel laggy.
When live mode is on, we can call `addEvent` API to add the latest events into the replayer:
Here is how you introduce a buffer:
```js
replayer.addEvent(NEW_EVENT);
const BUFFER_MS = 1000;
replayer.startLive(Date.now() - BUFFER_MS);
```
This will let the replay always delay 1 second than the source. If the time of data transportation is not longer than 1 second, the user will not feel laggy.