argo-cd/docs/user-guide/sync-waves.md
Regina Scott 5f10461034
fix: minor cleanup for wording in cli and docs (#5321)
* fix: various docs grammar fixes

Signed-off-by: Regina Scott <rescott@redhat.com>
2021-01-28 14:46:57 -08:00

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# Sync Phases and Waves
>v1.1
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Argo CD executes a sync operation in a number of steps. At a high-level, there are three phases *pre-sync*, *sync* and *post-sync*.
Within each phase you can have one or more waves, that allows you to ensure certain resources are healthy before subsequent resources are synced.
## How Do I Configure Phases?
Pre-sync and post-sync can only contain hooks. Apply the hook annotation:
```yaml
metadata:
annotations:
argocd.argoproj.io/hook: PreSync
```
[Read more about hooks](resource_hooks.md).
## How Do I Configure Waves?
Specify the wave using the following annotation:
```yaml
metadata:
annotations:
argocd.argoproj.io/sync-wave: "5"
```
Hooks and resources are assigned to wave zero by default. The wave can be negative, so you can create a wave that runs before all other resources.
## How Does It Work?
When Argo CD starts a sync, it orders the resources in the following precedence:
* The phase
* The wave they are in (lower values first)
* By kind (e.g. namespaces first)
* By name
It then determines the number of the next wave to apply. This is the first number where any resource is out-of-sync or unhealthy.
It applies resources in that wave.
It repeats this process until all phases and waves are in-sync and healthy.
Because an application can have resources that are unhealthy in the first wave, it may be that the app can never get to healthy.