Allow providing separate host/port parameters for Redis scaler

[marchmallow]

Use-Case

The config for the Redis Lists scaler requires the following format for the host/port:

address: REDIS_HOST # Required host:port format

In our deployments we have separate env vars for hosts and ports, so would like to have an alternative to provide this information in separate parameters, similarly to how it is allowed for PostgreSQL and MySQL scalers.

Specification

• Keep address param working as is
• Add host and port parameters (look at implementation of MySQL/PostgreSQL as example)
• Add config check and log an error if both address and host/port provided

[marchmallow]

@inuyasha82 is working on a prototype of this, we would like to know if you folks agree with adding this and any suggestion welcome. Thanks!

[tomkerkhove]

That's a good point actually - I'm not sure if I'd bite the bullet and remove address or stick with both scenarios.

Thoughts by others?

[inuyasha82]

@tomkerkhove
i think one problem is that scalers are not really standardized, so every scaler has a different behaviour.

i.e some like the redis scaler supporot only one format, usually host:port with different naming (redis has address, others have host, etc).

some like postgresql scaler have support for both format, host, port, and host:port but in this case is called "connection".

maybe some scalers doesn't support the host:port format.

[tomkerkhove]

@zroubalik @jeffhollan What do you think about this? Should we take this standardization into account for 2.0?

[zroubalik]

I think we should, but I currently don't know all details about all scalers to make an informed decision. Therefore I don't know whether standardization is a good approach or not -> Do all scalers have similar needs/fields/paramteres to follow standardized format (given the nature of the scalers source, ie. queue/event/...)? Do we want to bring some partial mandatory format? Won't it bring unnecessary mess? We might need an analysis across all scalers, what parameters they are using and which way to see whether there is possibility to create some standard format.

[marchmallow]

From looking at a number of the scalers which have proper docs linked at https://keda.sh/ I found one at least does not need this type of information: https://keda.sh/scalers/gcp-pub-sub/ but many others do and they are far from consistent. Most seem to only accept a single param that should contain host:port info, and the name of the parameter varies a lot, some examples: serverAddress, natsServerMonitoringEndpoint, connection, address

[marchmallow]

I think it would make it simpler to learn how to work with different queues if this was a bit more standard.

[tomkerkhove]

What I'm reading is that:

1. We should not enforce mandatory fields
2. Create a list of commonly used parameters and assign a default name
   • Example - Connection strings use a variety of names, but we should standardize on connectionString or connection
3. We need to do the same for addresses in format of host:port, but provide alternative names for just host & port as well.
4. In case of 3, both approaches are ok and we should standardize on which approach (full or seperate) to favorite over the other

Can everybody agree with that? If so, I'll create a dedicated issue for that.

In terms of #694 itself, totally agree that we should add it but prefer address indeed

[inuyasha82]

@tomkerkhove yeah, i agree with your conclusions, as per 1 when you talk about mandatory fields, are u referring to some fields that should be commond in all scalers?
Cause think that every scaler needs some mandatory fields in order to establish the connection, but of course every queue needs different mandatory fields.

2. Yeah i think it could be a good idea, makes things easier
3. 4. yeah definetely!

[inuyasha82]

Hi everyone, just to let u know that i created PR #710 to implement this request.

[tomkerkhove]

Thanks @inuyasha82!

See #712 for standardization!

[marchmallow]

I think we can close this