Add glossary item for "pull"

[todaywasawesome]

From this discussion: open-gitops/project#134

In light of ongoing discussions and questions in slack, of which this is the most recent example, it seems prudent to explain what pull means.

Sometimes, readers understand "pull" to mean that GitOps agents must live in the infrastructure under management so that it is self-sufficient and does not require external agents. This however, is not the intention of the word pull. The word pull here is specifically in reference to how desired state is discovered.

Signed-off-by: Dan Garfield dan@codefresh.io

Signed-off-by: Dan Garfield dan@todaywasawesome.com

[ubaumann]

I would like it if there would be something about the fact, that the GitOps agent needs to be able to access the SSoT at any time.

Maybe we add the following sentence?

In contrast to traditional, CI/CD pipelines which "push" event based triggers to discover state changes, in GitOps desired state is "pulled". The GitOps agents need to be able to access the desired state at any time to avoid drifts. This state may be reconciled with local or remote actual states. In GitOps agents are expected to pull both desired and actual states without the requirement of events. Webhooks may be used to speed up this process, but should a webhook fail, the agent is still expected to discover changes to desired state by pulling from the source of truth.

[scottrigby]

Thanks @todaywasawesome for hopping on this.

@ubaumann I agree, from Slack and elaborated in this discussion answer open-gitops/project#134 (comment) WDYT?

[scottrigby]

Dan what do you think about this? building on what you wrote but also with more direct ties to existing content. If so you can merge this suggestion into your PR branch directly (number 3 in Incorporating feedback in your pull request).

[scottrigby]

Great 👍 Now just looks like DCO bot is unhappy with email mismatch:

Commit sha: 984ed8e, Author: Dan Garfield, Committer: GitHub; Can not find "Dan Garfield dan@todaywasawesome.com", in ["Dan Garfield dan@codefresh.io", "Dan Garfield dan@codefresh.io"].

Steps to fix: https://github.com/open-gitops/documents/runs/12166015365

[ubaumann]

@todaywasawesome Looks good to me! It makes it much more straightforward. Thanks

[scottrigby]

After merging this, we can create a v1.1.0 draft similar to how we did 1.0.0.

[niklasmtj]

LGTM

[scottrigby]

Ok this has been open for review in its current state for a good while now, has multiple collaborators/co-authors, and 4 maintainer approvals. Merging. Thanks everyone! 🚀