backstage/plugins/linguist-backend

Linguist Backend

Welcome to the Linguist backend plugin! This plugin provides data for the Linguist frontend features.

Setup

The following sections will help you get the Linguist Backend plugin setup and running.

Up and Running

Here's how to get the backend up and running:

1. First we need to add the @backstage/plugin-linguist-backend package to your backend:

   # From the Backstage root directory
   cd packages/backend
   yarn add @backstage/plugin-linguist-backend
   

2. Then we will create a new file named packages/backend/src/plugins/linguist.ts, and add the following to it:

   import { TaskScheduleDefinition } from '@backstage/backend-tasks';
   import { createRouter } from '@backstage/plugin-linguist-backend';
   import { Router } from 'express';
   import type { PluginEnvironment } from '../types';
   
   export default async function createPlugin(
     env: PluginEnvironment,
   ): Promise<Router> {
     const schedule: TaskScheduleDefinition = {
       frequency: { minutes: 2 },
       timeout: { minutes: 15 },
       initialDelay: { seconds: 90 },
     };
   
     return createRouter({ schedule: schedule }, { ...env });
   }
   

3. Next we wire this into the overall backend router, edit packages/backend/src/index.ts:

   import linguist from './plugins/linguist';
   // ...
   async function main() {
     // ...
     // Add this line under the other lines that follow the useHotMemoize pattern
     const linguistEnv = useHotMemoize(module, () => createEnv('linguist'));
     // ...
     // Insert this line under the other lines that add their routers to apiRouter in the same way
     apiRouter.use('/linguist', await linguist(linguistEnv));
   

4. Now run yarn start-backend from the repo root

5. Finally open http://localhost:7007/api/linguist/health in a browser and it should return {"status":"ok"}

Batch Size

The Linguist backend is setup to process entities by acting as a queue where it will pull down all the applicable entities from the Catalog and add them to it's database (saving just the entityRef). Then it will grab the n oldest entities that have not been processed to determine their languages and process them. To control the batch size simply provide that to the createRouter function in your packages/backend/src/plugins/linguist.ts like this:

return createRouter({ schedule: schedule, batchSize: 40 }, { ...env });

Note: The default batch size is 20

Kind

The default setup only processes entities of kind ['API', 'Component', 'Template']. To control the kind that are processed provide that to the createRouter function in your packages/backend/src/plugins/linguist.ts like this:

return createRouter({ schedule: schedule, kind: ['Component'] }, { ...env });

Refresh

The default setup will only generate the language breakdown for entities with the linguist annotation that have not been generated yet. If you want this process to also refresh the data you can do so by adding the age (as a HumanDuration) in your packages/backend/src/plugins/linguist.ts when you call createRouter:

return createRouter({ schedule: schedule, age: { days: 30 } }, { ...env });

With the age setup like this if the language breakdown is older than 15 days it will get regenerated. It's recommended that if you choose to use this configuration to set it to a large value - 30, 90, or 180 - as this data generally does not change drastically.

Linguist JS options

The default setup will use the default linguist-js options, a full list of the available options can be found here.

return createRouter(
  { schedule: schedule, linguistJsOptions: { offline: true } },
  { ...env },
);

Use Source Location

You may wish to use the backstage.io/source-location annotation over using the backstage.io/linguist as you may not be able to quickly add that annotation to your Entities. To do this you'll just need to set the useSourceLocation boolean to true in your packages/backend/src/plugins/linguist.ts when you call createRouter:

return createRouter(
  { schedule: schedule, useSourceLocation: true },
  { ...env },
);

Note: This has the potential to cause a lot of processing, be very thoughtful about this before hand

Links

• Frontend part of the plugin
• The Backstage homepage