chore: add feature flag for using replica to look up redirects

README.md

@@ -146,6 +146,7 @@ After these have been set up, set the environment variables according to the tab
 |API_LINK_RANDOM_STR_LENGTH|No|String length of randomly generated shortUrl in API created links. Defaults to 8|
 |FF_EXTERNAL_API|No|Boolean, feature flag for enabling the external and admin API. Defaults to false|
 |ADMIN_API_EMAILS|No|Emails with admin API access, separated by commas without spaces. Defaults to none.|
+|FF_USE_REPLICA_FOR_REDIRECTS|No|Boolean, feature flag for using the replica database to look up redirects to long URLs. Defaults to false|
 
 #### Serverless functions for link migration
 

src/server/config.ts

@@ -194,6 +194,8 @@ export const databaseUri = process.env.DB_URI as string
 export const masterDatabaseCredentials = parseDbUri(databaseUri)
 export const replicaUri = process.env.REPLICA_URI as string
 export const replicaDatabaseCredentials = parseDbUri(replicaUri)
+export const ffUseReplicaForRedirects =
+  process.env.FF_USE_REPLICA_FOR_REDIRECTS === 'true'
 export const redisOtpUri = process.env.REDIS_OTP_URI as string
 export const redisSessionUri = process.env.REDIS_SESSION_URI as string
 export const redisRedirectUri = process.env.REDIS_REDIRECT_URI as string

src/server/repositories/UrlRepository.ts

@@ -7,7 +7,7 @@ import { Url, UrlType } from '../models/url'
 import { UrlClicks } from '../models/statistics/clicks'
 import { NotFoundError } from '../util/error'
 import { redirectClient } from '../redis'
-import { logger, redirectExpiry } from '../config'
+import { ffUseReplicaForRedirects, logger, redirectExpiry } from '../config'
 import { sequelize } from '../util/sequelize'
 import { DependencyIds } from '../constants'
 import { FileVisibility, S3Interface } from '../services/aws'
@@ -484,7 +484,10 @@ export class UrlRepository implements UrlRepositoryInterface {
    */
   private getLongUrlFromDatabase: (shortUrl: string) => Promise<string> =
     async (shortUrl) => {
-      const url = await Url.scope('useReplica').findOne({
+      const url = await (ffUseReplicaForRedirects
+        ? Url.scope('useReplica')
+        : Url
+      ).findOne({
         where: { shortUrl, state: StorableUrlState.Active },
       })
       if (!url) {