Quality gates for channeled artifacts

Channels is a software release concept that is similar to semver, and look like this: track/risk/branch.

For example:

Track	Risk	Branch	Potetnail use case
latest	edge	pr-99	Ephemeral builds during the PR process
2.x	edge		Latest merge into the `2.x` git branch
	beta
	candidate
	stable

(You can choose how to name tracks and branches, but risk must be one of the above.)

Quality guarantees¶

Tagging commits with semver tags is common practice, so what value channels give us? Depends on how we practice promotion across channels :)

If we gate risk promotion with some compute effort, then each risk could represent quality guarantees. For example:

graph LR
edge -->|8 hours| beta -->|2 days| candidate -->|1 week| stable

Identify audiences and expectations¶

Ideally, we'd want to run all tests before merging into main (and that way we wouldn't even need any channels!), but that is often impractical, because of how long some tests may take.

Think of the risk level as an "inverted funnel": the less risky it is, the larger the audience that is consuming it.

Risk	Hypothetical audience	Min. due-diligence expected by audience
edge	Your team	Unit tests, integration tests pass; 'it works'
beta	Other product teams in your department	Works on various OS/K8s/etc. versions
candidate	QA team	Integratable with other products
stable	Entire community	Backwards compatibility, no performance degradation, multi-substrate support

Classify tests into duration bins¶

Here's an example.

Quality gate (risk promotion)	Test duration	Kinds of tests
edge to beta	Less than 8 hours	Matrix tests for infra versions (LXD/K8s/Juju)
beta to candidate	Less than 2 days	Isolated load test (should be longer than double the longest period in the application)
candidate to stable	More than 2 days	End-to-end solution tests over multiple substrates

Auto-promote!¶

When tests pass, auto promote to the next risk level. This is also known as continuous delivery :)