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diff --git a/docs/basics/update.md b/docs/basics/update.md new file mode 100644 index 0000000..30da0f7 --- /dev/null +++ b/docs/basics/update.md @@ -0,0 +1,85 @@ +# Updating container images + +## General process overview + +Argo CD Image Updater can update container images managed by one or more of +your Argo CD applications, according to how it is configured. + +The workflow of Argo CD Image Updater can be described as follows: + +* It scans for currently configured Argo CD `Application` resources either + using the Kubernetes or the Argo CD API (depending on how you installed + the Argo CD Image Updater). The `Applications` to consider can be further + limited by having Argo CD Image Updater selecting only those applications + whose name match a given pattern, or match a given label. + +* It then goes through the list of `Applications` found and inspects each + for the the annotation `argocd-image-updater.argoproj.io/image-list`. This + annotation holds a list of image names that should be updated, and is a + mandatory annotation for Argo CD Image Updater to indicate it should + process this `Application`. Read more about the syntax expected in this + annotations's value in the [marking images for update](#TODO) + section in this doc. + +* For each image found in the list, Argo CD Image Updater will first check + if this image is actually deployed with the application. It does a strict + check for the complete image name, including the registry the image is + pulled from. For example, `docker.io/some/image` and `quay.io/some/image`, + while both referring to `some/image`, are not considered equal. This strict + behavior can be relaxed, however. See [forcing image updates](#TODO) for + further explanation. + +* If Argo CD Image Updater considers an image from the list eligible for an + update check, it will connect the corresponding container registry to see + if there is a newer version of the image according to the + [update strategy](../strategies/) + and other constraints that may have been configured for the image (e.g. + a list of tags that are allowed to consider). + +* If a newer version of an image was found, Argo CD Image Updater will try + to update the image according to the configured + [update method](../methods/). Please note that Argo CD Image Updater will + never update your manifests, instead it re-configures your Application + sources to use the new image tag, and control is handed over to Argo CD. + +## <a name="multi-arch"></a>Multi-arch images and clusters + +As of version 0.12, Argo CD Image Updater has full support for multi-arch +images (and multi-arch clusters) by being able to inspect images with multiple +manifests (i.e. a manifest list). + +Multi-arch currently only is supported for +[update strategies](../basics/update-strategies.md) +which fetch image meta-data: `latest` and `digest`. Multi-arch will be ignored +for the update strategies that do not fetch meta-data, `semver` and `name`. + +By default, Argo CD Image Updater will only consider updating to images that +have a manifest for the same platform where itself runs on. If you are on a +cluster that has nodes of multiple architectures, and are pinning certain +workloads to certain nodes, you will have to tell Argo CD Image Updater which +platforms are allowed for a certain application or an image. This can be done +by setting an appropriate +[annotation per image](../configuration/images.md#platforms) +or for all images of a given +[application as a default setting](../configuration/images.md#appendix-defaults). + +Multi-arch is also implemented by the +[test command](../install/testing.md#multi-arch). + +## Sync policies and image updates + +As explained above, the Argo CD Image Updater will assume that Argo CD will +update the manifests in your cluster to use any new image that has been set +by the Argo CD Image Updater. + +Argo CD Image Updater will work best with automatic syncing enabled for the +Argo CD applications that are being updated. + +## Rollback and image updates + +Currently, Argo CD Image Updater does not honor the rollback status of an +Argo CD application, and keeps updating to new images also for Applications +that are being rolled back. However, Argo CD will disable auto-sync for +such applications. + +Honoring rollbacked applications correctly is on our roadmap. |