Deploying a Custom Policy for Flex Gateway in Local Mode

You can implement custom policies via WebAssembly (WASM) extensions that run on Envoy as custom filters. The following steps demonstrate deploying and applying a custom filter (policy) to an API running in Local Mode:

Create a configuration YAML file.
Save the file in the Flex Gateway configuration directory.
Create the extension definition.
Encode the custom policy WASM implementation using base64.
Link the extension definition to the custom policy WASM binary implementation.
Link the custom policy to an API instance.
Apply the resources to the Flex Gateway instance.

Before You Begin

Before getting started, ensure that you have:

Flex Gateway installed and running in Local Mode. See Downloading Flex Gateway for more information about installing and running the gateway.
Your upstream service URL. See Publishing a Simple API in Local Mode for an example.
A custom policy implemented and compiled. See Implement a Flex Gateway Custom Policy in Rust.

Deploy a Custom Policy

Create a configuration file called custom-policy-example.yaml.
Save the file in the Flex Gateway configuration directory. For example:
- /etc/mulesoft/flex-gateway/conf.d/policies
Create the extension definition.

Copy and paste the following YAML snippet into the new configuration file. The YAML defines the configuration and metadata properties for the custom policy:
```
apiVersion: gateway.mulesoft.com/v1alpha1
kind: Extension
metadata:
  name: custom-local-example-definition
spec:
  extends:
  - name: extension-authentication
  - name: extension-definition
  properties:
    secret-value:
      type: string
  required:
    - secret-value
```
- The metadata.name value contains the extension name.
- The Extension inherits properties from other defined extensions. For example, spec.extends specifies that the extension is an extension-definition, and that it belongs in the authentication category (extension-authentication).
- The spec.properties values define properties that configure the custom policy instance.
- The spec.required value specifies the required properties.

Encode the custom policy WASM binary implementation using base64.

Encode the custom policy WASM binary implementation by executing the following command:

base64 <your-custom-policy-name>.wasm | tr -d '\n\r' > policy

The command sends the encoded data to a file called policy. In the next step, substitute <WASM_BINARY_IN_BASE64> with this encoded data.

If you compiled the policy using a target of wasm32-unknown-unknown, locate the binary in ./target/wasm32-unknown-unknown/release.

If you compiled the policy using a target of wasm32-wasi, locate the binary in ./target/wasm32-wasi/release.

Link the extension definition to the custom policy WASM binary implementation.

In custom-policy-example.yaml, define another resource that contains the policy implementation:

apiVersion: gateway.mulesoft.com/v1alpha1
kind: Extension
metadata:
  name: custom-local-example-flex
spec:
  extends:
    - name: custom-local-example-definition
    - name: envoy-filter
    - name: proxy-wasm-filter
  properties:
    rootId:
      type: string
      default: main
    implementation:
      type: string
      default: base64://<WASM_BINARY_IN_BASE64>

The metadata.name value contains the policy name, which must be different from the name specified in the definition.
The spec.extends value specifies the resource definition to inherit from. For example, custom-local-example-definition is the resource previously defined.

Substitute the <WASM_BINARY_IN_BASE64> value of spec.properties.implementation.default with the base64 encoded WASM binary data, generated previously.

You can include the policy definition and implementation in the same Extension resource, but this generates a tighter coupling between them. It is therefore recommended to separate the two into different resources.

Link the custom policy to an API instance.

In custom-policy-example.yaml, define another resource that links the policy to an API instance:
```
apiVersion: gateway.mulesoft.com/v1alpha1
kind: PolicyBinding
metadata:
  name: custom-local-example
spec:
  targetRef:
    kind: ApiInstance
    name: ingress-http
  policyRef:
    kind: Extension
    name: custom-local-example-flex
  config:
    secret-value: "an-example-value"
```
- The metadata.name value contains the custom policy instance name.
- The spec.targetRef.name value contains the name of the API instance on which to apply the custom policy. The API instance must already have been defined and applied.
- The spec.policyRef.name value contains the custom policy implementation to apply.
- The spec.config value contains policy configuration data.

Apply the resources to the Flex Gateway instance.

The complete custom-policy-example.yaml file now contains the following:

---
apiVersion: gateway.mulesoft.com/v1alpha1
kind: Extension
metadata:
  name: custom-local-example-definition
spec:
  extends:
  - name: extension-authentication
  - name: extension-definition
  properties:
    secret-value:
      type: string
  required:
    - secret-value
---
apiVersion: gateway.mulesoft.com/v1alpha1
kind: Extension
metadata:
  name: custom-local-example-flex
spec:
  extends:
    - name: custom-local-example-definition
    - name: envoy-filter
    - name: proxy-wasm-filter
  properties:
    rootId:
      type: string
      default: main
    implementation:
      type: string
      default: base64://<WASM_BINARY_IN_BASE64>
---
apiVersion: gateway.mulesoft.com/v1alpha1
kind: PolicyBinding
metadata:
  name: custom-local-example
spec:
  targetRef:
    kind: ApiInstance
    name: ingress-http
  policyRef:
    kind: Extension
    name: custom-local-example-flex
  config:
    secret-value: "an-example-value"

Save the file in the Flex Gateway configuration directory. For example:

/etc/mulesoft/flex-gateway/conf.d/policies

A custom policy now applies to an API instance called ingress-http.

Deploying a Custom Policy for Flex Gateway in Local Mode

Before You Begin

Deploy a Custom Policy

See Also