Use setInterval in projections

EventStoreDB
1

Hello

Is it possible to use setInterval in a projection?

class BulkBooksBuffer {
static init(s, e) {
return {
count: 0,
books: [],
sequence: 1,
metadata: {
EventClrType: ‘Library.BooksReadyEvent, Library’,
UserName: ‘’,
AuthenticationType: ‘’
}
};
}

static onBulkBookFinishedEvent(s, e) {
    s.books.push(e.data.streamId);
    s.count += 1;

    **if (s.count == 10) {**
        if (s.count > 0) {
        emit('Bulk-Books-Ready',
            'BulkBooksReadyEvent',
            { Books: s.books, Sequence: s.sequence },
            s.metadata);
        s.count = 0;
        s.books = [];
        s.sequence += 1;
    }
    }
}

}

fromStream(‘Bulk-Books’)
.when({
$init: BulkBooksBuffer.init,
BulkBookFinishedEvent: BulkBooksBuffer.onBulkBookFinishedEvent
});

In the above code, I would like to emit an event if count is equal to 10 or after 5 seconds. Whichever comes first.

Where can I write the setInterval function?

Many thanks.

2

easiest way to do this is to have a service (or cron etc) emit an event to a stream every n seconds. Then set $maxAge/$maxCount on it so they disappear over time.

3

Great. Thanks for the fast reply.