Changing `tlogReplicas` property on existing collections in Solr Cloud

[Nikolay Ivanov <in...@vmware.com.INVALID>]

Hello guys,

I have an issue that I cannot find an answer to. Can you please try to assist me?
I will briefly explain our setup: We, at VMWare, have a Solr Cloud cluster setup(ver. 8.9). We are using TLOG replication of 3. Due to underutilized replicas, we are considering of decreasing the tlogReplicas to 2(to save some cost).
We have a set of collections in production, so I want to smoothly make that transition.
The only problem I have so far is that it seems I cannot change `tlogReplicas` property using the MODIFYCOLLECTION API.
Is there any other way I can smoothly change `tlogReplicas` property of an existing collection without recreating it?

Thanks a lot for the help,
Nikolay Ivanov

Re: Changing `tlogReplicas` property on existing collections in Solr Cloud

[Shawn Heisey <ap...@elyograg.org>]

On 2/22/23 01:39, Nikolay Ivanov wrote:
> Hello guys,
>
> I have an issue that I cannot find an answer to. Can you please try to assist me?
> I will briefly explain our setup: We, at VMWare, have a Solr Cloud cluster setup(ver. 8.9). We are using TLOG replication of 3. Due to underutilized replicas, we are considering of decreasing the tlogReplicas to 2(to save some cost).
> We have a set of collections in production, so I want to smoothly make that transition.
> The only problem I have so far is that it seems I cannot change `tlogReplicas` property using the MODIFYCOLLECTION API.
> Is there any other way I can smoothly change `tlogReplicas` property of an existing collection without recreating it?

I can't find any mention of anything that actually USES that property.  
Maybe autoscaling does, but I haven't found any evidence supporting 
that.  I'm not sure that has any meaning outside the initial collection 
creation.

If you want fewer replicas, just delete one.  If the cluster doesn't 
automatically recreate it, then that will be the end of it.

Thanks,
Shawn