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Signed-off-by: Michael Crenshaw <350466+crenshaw-dev@users.noreply.github.com> Signed-off-by: Michael Crenshaw <350466+crenshaw-dev@users.noreply.github.com>
88 lines
4.5 KiB
Markdown
88 lines
4.5 KiB
Markdown
# Parameter Overrides
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Argo CD provides a mechanism to override the parameters of Argo CD applications that leverages config management
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tools. This provides flexibility in having most of the application manifests defined in Git, while leaving room
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for *some* parts of the k8s manifests determined dynamically, or outside of Git. It also serves as an alternative way of
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redeploying an application by changing application parameters via Argo CD, instead of making the
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changes to the manifests in Git.
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!!! tip
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Many consider this mode of operation as an anti-pattern to GitOps, since the source of
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truth becomes a union of the Git repository, and the application overrides. The Argo CD parameter
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overrides feature is provided mainly as a convenience to developers and is intended to be used in
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dev/test environments, vs. production environments.
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To use parameter overrides, run the `argocd app set -p (COMPONENT=)PARAM=VALUE` command:
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```bash
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argocd app set guestbook -p image=example/guestbook:abcd123
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argocd app sync guestbook
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```
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The `PARAM` is expected to be a normal YAML path
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```bash
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argocd app set guestbook -p ingress.enabled=true
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argocd app set guestbook -p ingress.hosts[0]=guestbook.myclusterurl
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```
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The `argocd app set` [command](./commands/argocd_app_set.md) supports more tool-specific flags such as `--kustomize-image`, `--jsonnet-ext-var-str` etc
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flags. You can also specify overrides directly in the source field on application spec. Read more about supported options in corresponded tool [documentation](./application_sources.md).
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## When To Use Overrides?
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The following are situations where parameter overrides would be useful:
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1. A team maintains a "dev" environment, which needs to be continually updated with the latest
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version of their guestbook application after every build in the tip of master. To address this use
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case, the application would expose a parameter named `image`, whose value used in the `dev`
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environment contains a placeholder value (e.g. `example/guestbook:replaceme`). The placeholder value
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would be determined externally (outside of Git) such as a build system. Then, as part of the build
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pipeline, the parameter value of the `image` would be continually updated to the freshly built image
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(e.g. `argocd app set guestbook -p image=example/guestbook:abcd123`). A sync operation
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would result in the application being redeployed with the new image.
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2. A repository of Helm manifests is already publicly available (e.g. https://github.com/helm/charts).
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Since commit access to the repository is unavailable, it is useful to be able to install charts from
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the public repository and customize the deployment with different parameters, without resorting to
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forking the repository to make the changes. For example, to install Redis from the Helm chart
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repository and customize the database password, you would run:
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```bash
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argocd app create redis --repo https://github.com/helm/charts.git --path stable/redis --dest-server https://kubernetes.default.svc --dest-namespace default -p password=abc123
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```
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## Store Overrides In Git
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The config management tool specific overrides can be specified in `.argocd-source.yaml` file stored in the source application
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directory in the Git repository.
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The `.argocd-source.yaml` file is used during manifest generation and overrides
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application source fields, such as `kustomize`, `helm` etc.
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Example:
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```yaml
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kustomize:
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images:
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- gcr.io/heptio-images/ks-guestbook-demo:0.2
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```
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The `.argocd-source` is trying to solve two following main use cases:
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- Provide the unified way to "override" application parameters in Git and enable the "write back" feature
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for projects like [argocd-image-updater](https://github.com/argoproj-labs/argocd-image-updater).
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- Support "discovering" applications in the Git repository by projects like [applicationset](https://github.com/argoproj/applicationset)
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(see [git files generator](https://github.com/argoproj/argo-cd/blob/master/applicationset/examples/git-generator-files-discovery/git-generator-files.yaml))
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You can also store parameter overrides in an application specific file, if you
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are sourcing multiple applications from a single path in your repository.
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The application specific file must be named `.argocd-source-<appname>.yaml`,
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where `<appname>` is the name of the application the overrides are valid for.
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If there exists an non-application specific `.argocd-source.yaml`, parameters
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included in that file will be merged first, and then the application specific
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parameters are merged, which can also contain overrides to the parameters
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stored in the non-application specific file.
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