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| 1 | +# Webhook Configuration Installation |
| 2 | + |
| 3 | +Installing webhook configurations requires higher privileges which manager's service account might not have. |
| 4 | +In that case, a separate process with higher privileges would like to install the webhook configurations. |
| 5 | + |
| 6 | +There are 2 options to install webhook configurations into a cluster: |
| 7 | + |
| 8 | +- Configure the Webhook Server to automatically install the webhook configurations when it starts. |
| 9 | +- Use the webhook manifests generator to generate webhook configurations. |
| 10 | +Then install the webhook configurations and deploy the webhook servers. |
| 11 | + |
| 12 | +## Webhook Installer |
| 13 | + |
| 14 | +Webhook installer is a feature provided by the [controller-runtime](https://godoc.org/sigs.k8s.io/controller-runtime/pkg/webhook) library. |
| 15 | +For a [Webhook Server](https://godoc.org/sigs.k8s.io/controller-runtime/pkg/webhook#Server), |
| 16 | +you can choose to enable the webhook installer. |
| 17 | +Depending on your [ServerOptions](https://godoc.org/sigs.k8s.io/controller-runtime/pkg/webhook#ServerOptions), |
| 18 | +the installer may install [mutatingWebhookConfigurations](https://github.com/kubernetes/api/blob/9fcf73cc980bd64f38a4f721a7371b0ebb72e1ff/admissionregistration/v1beta1/types.go#L113-L124), |
| 19 | +[validatingWebhookConfigurations](https://github.com/kubernetes/api/blob/9fcf73cc980bd64f38a4f721a7371b0ebb72e1ff/admissionregistration/v1beta1/types.go#L83-L94) |
| 20 | +and service; it may also update the secret if needed. |
| 21 | + |
| 22 | +To make the webhook installer work correctly, please ensure the manager's service account has |
| 23 | +the right permissions. For example. it may need permissions: |
| 24 | +- create and update MutatingWebhookConfigurations and ValidatingWebhookConfigurations |
| 25 | +- create and update the Service in the same namespace of the manager |
| 26 | +- update the Secret in the same namespace of the manager |
| 27 | + |
| 28 | +The service fronts the webhook server. |
| 29 | +So please ensure the service's selectors select your webhook server pods. |
| 30 | + |
| 31 | +The secret contains |
| 32 | +- the serving certificate and its corresponding private key |
| 33 | +- the signing CA certificate and its corresponding private key |
| 34 | + |
| 35 | +Webhook installer can be very helpful for |
| 36 | +- faster iteration during development |
| 37 | +- easier deployment in production if policy allows |
| 38 | + |
| 39 | +Webhook installer is on by default. Set |
| 40 | +[`DisableWebhookConfigInstaller`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L57-L60) |
| 41 | +to true to turn it off. |
| 42 | + |
| 43 | +## Webhook Manifests Generator |
| 44 | + |
| 45 | +From cluster administrators perspective, they may want to have the webhook configurations |
| 46 | +installation to be a separate process from running the webhook server, |
| 47 | +since permissions to create and update webhook configurations are considered as high privileges. |
| 48 | + |
| 49 | +Similar to other generators in [controller-tools](https://github.com/kubernetes-sigs/controller-tools), |
| 50 | +webhook manifest generator is annotation-driven. |
| 51 | + |
| 52 | +How the webhook manifest generator works |
| 53 | +1) It parses the annotations to configure |
| 54 | +[Webhook](https://godoc.org/sigs.k8s.io/controller-runtime/pkg/webhook/admission#Webhook). |
| 55 | +1) It parses the annotations to configure |
| 56 | +[ServerOptions](https://godoc.org/sigs.k8s.io/controller-runtime/pkg/webhook#ServerOptions). |
| 57 | +1) It uses the library in controller-runtime, which is the same machinery as |
| 58 | +the installer, to generate the webhook configuration manifests. |
| 59 | + |
| 60 | +#### Comment Group |
| 61 | + |
| 62 | +A comment group represents a sequence of comments with no empty lines between. |
| 63 | +Comment group is a concept that is important for writing and parsing annotations correctly. |
| 64 | + |
| 65 | +For example, the following comments are in one comment group |
| 66 | + |
| 67 | +``` |
| 68 | +// +kubebuilder:webhook:groups=apps |
| 69 | +// +kubebuilder:webhook:resources=deployments |
| 70 | +``` |
| 71 | + |
| 72 | +The following comments are in 2 comments groups |
| 73 | + |
| 74 | +``` |
| 75 | +// +kubebuilder:webhook:groups=apps |
| 76 | +
|
| 77 | +// +kubebuilder:webhook:resources=deployments |
| 78 | +``` |
| 79 | + |
| 80 | +#### Annotations |
| 81 | + |
| 82 | +Each comment line that starts with `+kubebuilder:webhook:` will be processed to extract annotations. |
| 83 | + |
| 84 | +The annotations can be grouped in 2 categories based on what struct they configure. |
| 85 | + |
| 86 | +The _first_ category is for each individual webhook. |
| 87 | +They are used to set the fields in [`Webhook`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/admission/webhook.go#L55-L80) struct. |
| 88 | +The annotations for the same webhook are allowed to span across multiple lines as long as they are prefixed with |
| 89 | +`+kubebuilder:webhook:` and in the __same__ comment group. |
| 90 | +It is suggested to put this category of annotations in the same file as its corresponding webhook. |
| 91 | + |
| 92 | +For example, the following is for one single webhook |
| 93 | + |
| 94 | +``` |
| 95 | +// +kubebuilder:webhook:groups=apps,versions=v1,resources=deployments,verbs=create,update |
| 96 | +// +kubebuilder:webhook:name=mutating-create-update-deployment.testproject.org |
| 97 | +// +kubebuilder:webhook:path=/mutating-create-update-deployment |
| 98 | +// +kubebuilder:webhook:type=mutating,failure-policy=fail |
| 99 | +``` |
| 100 | + |
| 101 | +`groups`, `versions` and `resources` have the same semantic as the ones used for generating RBAC manifests. |
| 102 | +They can reference a core type or a CRD type. |
| 103 | + |
| 104 | +`verbs` are used to set [`Operations`](https://github.com/kubernetes/api/blob/9fcf73cc980bd64f38a4f721a7371b0ebb72e1ff/admissionregistration/v1beta1/types.go#L234-L243). |
| 105 | +It supports `create`, `update`, `delete`, `connect` and `*` case-insensitively. |
| 106 | + |
| 107 | +`name` is the name of the webhook and |
| 108 | +is used to set [`Name`](https://github.com/kubernetes/api/blob/9fcf73cc980bd64f38a4f721a7371b0ebb72e1ff/admissionregistration/v1beta1/types.go#L146). |
| 109 | +`path` is the endpoint that this webhook serves and |
| 110 | +is used to set [`Path`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/admission/webhook.go#L61-L62). |
| 111 | +Both `name` and `path` do NOT allow `,` and `;`. |
| 112 | + |
| 113 | +`type` indicates the webhook type which can be either `mutating` or `validating`. |
| 114 | + |
| 115 | +`failure-policy` is used to set [`FailurePolicy`](https://github.com/kubernetes/api/blob/9fcf73cc980bd64f38a4f721a7371b0ebb72e1ff/admissionregistration/v1beta1/types.go#L54-L61). |
| 116 | +It supports `fail` and `ignore` case-insensitively. |
| 117 | + |
| 118 | +The _second_ category is for the webhook server. |
| 119 | +All of them are used to configuration [`ServerOptions`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L39-L98) struct. |
| 120 | +Each annotation should only be used once. |
| 121 | +They don't have to be in the same comment group. |
| 122 | +It is suggested to put this category of annotations in the same file as the webhook server. |
| 123 | + |
| 124 | +The following is an example using webhook server annotations. |
| 125 | + |
| 126 | +``` |
| 127 | +// +kubebuilder:webhook:port=7890,cert-dir=/path/to/cert |
| 128 | +// +kubebuilder:webhook:service=test-system:webhook-service,selector=app:webhook-server |
| 129 | +// +kubebuilder:webhook:secret=test-system:webhook-secret |
| 130 | +// +kubebuilder:webhook:mutating-webhook-config-name=test-mutating-webhook-cfg |
| 131 | +// +kubebuilder:webhook:validating-webhook-config-name=test-validating-webhook-cfg |
| 132 | +``` |
| 133 | + |
| 134 | +`port` is the port that the webhook server serves. It is used to set [`Port`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L43). |
| 135 | + |
| 136 | +`service` should be formatted as `<namespace>:<name>`. It is used to set |
| 137 | +[the name and namespace of the service](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L102-L105). |
| 138 | + |
| 139 | +`selector` should be formatted as `key1:value1;key2:value2` and it has 2 usages: |
| 140 | +- use as [selectors in the service](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L106-L108) |
| 141 | +- use as additional labels that will be added to field `.spec.template.metadata.labels` of |
| 142 | +the StatefulSet through [`kustomize`](https://github.com/kubernetes-sigs/kustomize). |
| 143 | + |
| 144 | +`host` is used to set [`Host`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L87-L91). |
| 145 | + |
| 146 | +`secret` should be formatted as `<namespace>:<name>`. It is used to set [`Secret`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L73-L77) |
| 147 | + |
| 148 | +`mutating-webhook-config-name` is used to set [`MutatingWebhookConfigName`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L68-L69). |
| 149 | + |
| 150 | +`validating-webhook-config-name` is used to set [`ValidatingWebhookConfigName`](https://github.com/kubernetes-sigs/controller-runtime/blob/a8ea2056444a5d74d7408e4b8798cbe63b14066b/pkg/webhook/server.go#L70-L71). |
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