kedacore/keda

Provide capability to extend scalers

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#624 opened on Feb 11, 2020

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featurehelp wantedscaler

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Description

In certain scenarios it would be interesting to react based on what a certain scaler is doing.

For example; when processing a Service Bus/RabbitMQ queue but the queue does not exist it would be nice if we could react to that.

Proposal

We should provide the capability to opt-in for events which are emitted by a given scaler. With that, we could trigger a process to react. (Relates to https://github.com/kedacore/keda/issues/479)

Alternative

Alternative is to be able to define a job to run as part of the metadata, but personally I think it's best to decouple this from KEDA and provide the info but leave it up to others to handle it.

Other information

This came up on #KEDA in Kubernetes Slack for Tomek Święcicki his scenario.

Contributor guide

Research direction
Investigate the current scaler interface in KEDA and identify how to add an event emission mechanism. Look at existing scalers (e.g., Service Bus, RabbitMQ) to understand their lifecycle and determine where events could be emitted. Consider designing a callback or hook system for scalers to emit events that external components can subscribe to.
Tech stack
go
Domain
backendclouddevops
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GoKubernetes
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30