Write to same stream from multiple projections, or maxAge?

EventStoreDB
1

Hello,

I have events about Transactions that are first Received, then Confirmed, the Received event types can be removed after 7 days to save storage space, the Confirmed needs to stay forever.

To implement this I have two streams:

  • TxRecv $maxAge: 7 days
  • TxConf
    Both of these write to Streams through a Projection:

fromStream(‘TxRecv’)
.when({
$any: function(s, ev) {
linkTo(ev.metadata.address, ev)
}
})

fromStream(‘TxConf’)
.when({
$any: function(s, ev) {
linkTo(ev.metadata.address, ev)
}
})

``

This means I can subscribe to one Stream, the Address from the metadata to receive all events about Transactions to the Address.

However when I attempt to run this, I get the following: The ‘’ projection faulted due to ‘Multiple projections emitting to the same stream detected.’

I’m not sure why this would be an issue, as I can write to the same Stream with many different EventStore clients.

If I cannot do this, can I set a $maxAge on an individual EventData for it to be removed the from the system after the 7 day timeline?

Many thanks for any assistance.

James

2

Multiple projections cannot write to the same stream due as they would
conflict with each other (and it would be impossible to reset a
projection). That said if you are willing to give up the latter we are
introducing a "run with scissors" mode that would allow you to do just
this.

3

Thanks Greg - As usual when explaining a problem, I have resolved it two minutes after.

I am able to use the fromStreams function in a projection to collate the two streams together. Thank you for thinking of this case.

https://geteventstore.com/blog/20130210/the-cost-of-creating-a-stream/