This project has been created to demo: createBackendModule and scaffolderTemplatingExtensionPoint. See ticket here.
Note: Documentation about how to create a Scaffold backend module: https://github.com/backstage/backstage/blob/master/docs/backend-system/building-backends/08-migrating.md#the-scaffolder-plugin
The following section describe how to register, using the new backend system, a backend module able
to add Template filters that we will use within a Template scaffolded to perform operations like this : ${{ parameters.name | filter1 | filter2 | etc }}
- Create a backstage backend using backstage 1.25
npx @backstage/[email protected] --skip-install- Move to the project and add the needed dependencies
cd my-demo
yarn add --cwd packages/backend @backstage/backend-plugin-api
yarn add --cwd packages/backend @backstage/plugin-scaffolder-node
yarn add --cwd packages/backend @backstage/types- Create a backend module which uses as dependency:
scaffolderTemplatingExtensionPointand declare some filters using the function init functionscaffolderTemplating.addTemplateFilters. For this demo project, we will create this basicbase64filter:{ base64: (...args: JsonValue[]) => btoa(args.join(""))}
mkdir -p packages/backend/src/modules
cat <<EOF > packages/backend/src/modules/scaffoldTemplateFilters.ts
import {coreServices, createBackendModule} from '@backstage/backend-plugin-api';
import {scaffolderTemplatingExtensionPoint} from '@backstage/plugin-scaffolder-node/alpha';
import {JsonValue} from '@backstage/types';
export const myModule = createBackendModule({
pluginId: 'scaffolder',
moduleId: 'my-custom-filter',
register(env) {
env.registerInit({
deps: {
config: coreServices.rootConfig,
scaffolderTemplating: scaffolderTemplatingExtensionPoint,
},
async init({scaffolderTemplating}) {
scaffolderTemplating.addTemplateFilters(
{ base64: (...args: JsonValue[]) => btoa(args.join(""))}
);
},
});
},
});- Edit the file
my-demo/packages/backend/src/index.tsto import the new backend module
// Add the module: scaffoldTemplateFilters
backend.add(import('./modules/scaffoldTemplateFilters'));
...
backend.start()- Create a dummy template within the examples folder
cat <<EOF > ./examples/template/dummy.yaml
apiVersion: scaffolder.backstage.io/v1beta3
kind: Template
metadata:
name: dummy
title: Dummy template
description: Dummy template to test fields
spec:
owner: guests
type: service
# These parameters are used to generate the input form in the frontend, and are
# used to gather input data for the execution of the template.
parameters:
- title: input
required:
- myInput
properties:
myInput:
title: Input
type: string
description: Input
steps:
- id: debug
name: debug
action: debug:log
input:
message: \${{ parameters.myInput | base64 }}
EOF- Add it to the
app-config.yamlfile
...
# Local dummy template
- type: file
target: ../../examples/template/dummy.yaml
rules:
- allow: [Template]- Launch backstage locally
yarn dev- Open the
dummytemplate, add your name using theinputNamefield, click onreviewandcreatebutton - Check the log of the backstage backend application
type=incomingRequest
2024-04-05T12:14:34.973Z rootHttpRouter info ::1 - - [05/Apr/2024:12:14:34 +0000] "POST /api/scaffolder/v2/tasks HTTP/1.1" 201 45 "http://localhost:3000/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36" type=incomingRequest
info: {
"message": "Q2hhcmxlcw=="
}
info: Q2hhcmxlcw== - Create a backend module within the plugins folder of your backstage app project using the client:
npx @backstage/cli@latest new --select backend-module
npx @backstage/cli@latest new --select backend-module
? Enter the ID of the plugin [required] scaffolder
? Enter the ID of the module [required] my-custom-filter
cd - Rename the name of the new plugin package created from
"name": "backstage-plugin-scaffolder-backend-module-my-custom-filter",to"name": "@internal/backend-module-scaffolder-my-custom-filter", - Update the dependency name within the package.json of the backend application too
- Add the needed dependency to the plugin created:
yarn --cwd plugins/scaffolder-backend-module-my-custom-filter add @backstage/plugin-scaffolder-node yarn --cwd plugins/scaffolder-backend-module-my-custom-filter add @backstage/types
- Override the
createBackendModulefunction code within your filter definition:
... = createBackendModule({
pluginId: 'scaffolder',
moduleId: 'my-custom-filter',
register(env) {
env.registerInit({
deps: {
scaffolder: scaffolderTemplatingExtensionPoint,
},
async init({ scaffolder }) {
scaffolder.addTemplateFilters(
{base64: (...args: JsonValue[]) => btoa(args.join(""))}
);
},
});
},
});- Update the code of the
/Users/cmoullia/temp/backstage-next/backstage-backend-module/packages/backend/src/index.tsto comment the line importing the module locally// import scaffolderTemplatingExtension from './modules/scaffoldTemplateFilters'; - and import the module
backend.add(import('@internal/backend-module-scaffolder-my-custom-filter')); - Execute
yarn installto verify that the internal module is well imported - Launch backstage locally
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