# Upgrades, History and Rollbacks — Helm

Source: https://www.skillbyai.com/en/helm/u-upgrade

> Upgrade releases safely and roll back when something breaks.

## Every change is a revision

`helm upgrade RELEASE CHART` renders the chart with the new values and applies the difference to the cluster, creating a new revision. In pipelines, **`helm upgrade --install`** is the usual form: it installs the release if it does not exist and upgrades it otherwise, so the same command works on the first and the hundredth deployment. Add **`--wait`** so Helm waits until Deployments are ready (and `--timeout` to bound it); without it, Helm reports success as soon as the API accepts the objects, even if pods then crash. `helm history` lists revisions with their status and chart version, and **`helm rollback RELEASE REVISION`** re-applies an earlier revision's manifests as a new revision. Rollback restores Kubernetes objects, **not data**: a database migration run by the new version is not undone. Limit stored revisions with `--history-max` (default 10 for upgrades).

## Upgrade, observe, roll back

A failed upgrade leaves the release in a failed state; rollback returns to a known-good revision.

```bash
helm upgrade --install shop-api ./charts/shop-api -n shop \
  -f values-prod.yaml --set image.tag=2.8.0 \
  --wait --timeout 5m

# lists each revision with its status (deployed, superseded, failed), chart and description
helm history shop-api -n shop

# suppose revision 5 failed and revision 4 was good:
helm rollback shop-api 4 -n shop --wait   # creates revision 6 with revision 4's manifests
```

## Undo history in a document editor

Each upgrade is a saved version of the document. Rolling back restores the text from an older version, but if you emailed a copy to someone in between (a database migration), undo cannot recall the email.

**Quiz:** Why add --wait to helm upgrade in a CI pipeline?

- [ ] It makes rendering faster
- [x] So the command fails if workloads do not become ready, instead of reporting success too early
- [ ] It skips hooks
- [ ] It deletes old revisions

*Answer:* So the command fails if workloads do not become ready, instead of reporting success too early. Without --wait Helm succeeds once objects are accepted, even if the new pods never become ready.