Create Algolia i18n indices

Let's say we're creating an index for posts in two locales: en and de. We'll need to create two indices: indexName-en and indexName-de. Each index will contain posts in the respective locale.

1. Fetch data from Sanity for each locale

// lib/sanity.ts

import groq from 'groq'
import { createClient } from 'next-sanity'

// Hereinafter I've omitted explicit type definitions for brevity

const sanityClient = createClient({
  apiVersion: process.env.SANITY_API_VERSION,
  dataset: process.env.SANITY_DATASET,
  projectId: process.env.SANITY_PROJECT_ID
})

const query = groq`*[_type == "post" && !(_id in path("drafts.**")] {
    "objectID": _id,
    "title": title[$locale],
    "slug": slug.current,
  }`

export async function getPostsForLocale(
  locale: 'en' | 'de'
): Promise<IPost[]> {
  const data = await sanityClient.fetch(query, { locale })
  return data
}

2. Create a script that runs the index creation process for each locale.

// scripts/createIndex.ts

import algoliasearch from 'algoliasearch'

import { getPostsForLocale } from '@/lib/sanity'

const algoliaInstance = algoliasearch(
  process.env.ALGOLIA_APP_ID!,
  process.env.ALGOLIA_SEARCH_ADMIN_KEY!
)

const ALGOLIA_INDICES = [
  {
    indexName: 'indexName-en',
    locale: 'en'
  },
  {
    indexName: 'indexName-de',
    locale: 'de'
  }
]

async function createIndexForLocale(indexName, locale) {
  try {
    const index = algoliaInstance.initIndex(indexName)
    const data = await getPostsForLocale(locale)
    await index.saveObjects(indexData)
    console.log(
      `Saved ${data.length} docs to index: ${index.indexName}`
    )
    return {
      status: 200,
      body: 'Success!'
    }
  } catch (error) {
    console.error(error)
    return {
      status: 500,
      body: error
    }
  }
}

export default async function createIndex() {
  const promises = ALGOLIA_INDICES.map(({ indexName, locale }) =>
    createIndexForLocale(indexName, locale)
  )
  const results = await Promise.all(promises)
  return results
}

3. Create a route handler to run the script

// api/cron/route.ts

import createIndex from '@/scripts/createIndex'

export async function GET(req: Request) {
  if (
    req.headers.get('Authorization') !==
    `Bearer ${process.env.CRON_SECRET}`
  ) {
    return new Response(`Unauthorized`, { status: 401 })
  }
  try {
    await generateIndex()
    return new Response('Algolia index re-created', {
      status: 200
    })
  } catch (e) {
    const serializedError =
      e instanceof Error
        ? JSON.stringify(e, Object.getOwnPropertyNames(e))
        : 'Unknown error'
    return new Response(serializedError, { status: 500 })
  }
}

4. Setup Cron Job

Create a vercel.json file in your project's root directory

{
  "crons": [
    {
      "path": "/api/cron",
      "schedule": "0 0 * * 0"
    }
  ]
}

Cron is scheduled to run every Sunday at midnight. You can use crontab.guru to generate your own schedule.

5. Deploy to Vercel and test it out by running cron manually.