IS-310: Setup GrowthBook for BE (#926)

* feat: add growthbook as dep

* feat: add to env example

* feat: add polyfill deps for growthbook

* feat: add utils

* feat: setup types for growthbook

* feat: add extended type for request handler

* feat: add middleware

* feat: update middleware

* feat: add growthbook to convict

* feat: use middleware across routes

* feat: extract into constant file

* fix: add GB key to .env.test

* feat: enable auto-refresh

* feat: introduce interface for GrowthBook

* feat: add comment explaining new handler type

* fix: make return of custom handler type void

* fix: imports

* feat: inject attributes from authN middleware

* feat: inject site-name at authorization

* feat: add type safety for growthbook property in req

* fix: minor fixes

* feat: inject attributes from authN middleware

* feat: add growthbook as optional property in session context

* feat: inject growthbook into session

* feat: add type safety for GB

* feat: add key for ggs whitelist

* feat: update method to read from feature flag

* chore: remove env for ggs whitelist

* fix: remove unused constant

* feat: enable dev mode only for dev node env

* feat: remove dependency on ggs env var

* feat: make growthbook optional in Express request

* feat: add type safety

* feat: fix tests

* fix: conditional logic

* fix: log statement

* fix: remove role

* feat: add better logging for debugging

* fix: use logger instead of console

* feat: update function signatures

* feat: update tests

* feat: refactor flags to use namespaced references

.env-example

@@ -69,4 +69,7 @@ export NETLIFY_ACCESS_TOKEN=""
 export SGID_CLIENT_ID=""
 export SGID_CLIENT_SECRET=""
 export SGID_PRIVATE_KEY=""
-export SGID_REDIRECT_URI=""
+export SGID_REDIRECT_URI=""
+
+# GrowthBook
+export GROWTHBOOK_CLIENT_KEY=""

.env.test

@@ -78,4 +78,7 @@ export NETLIFY_ACCESS_TOKEN="blahblah"
 export SGID_CLIENT_ID="client"
 export SGID_CLIENT_SECRET="secret"
 export SGID_PRIVATE_KEY="private"
-export SGID_REDIRECT_URI="http://localhost:8081/v2/auth/sgid/auth-redirect"
+export SGID_REDIRECT_URI="http://localhost:8081/v2/auth/sgid/auth-redirect"
+
+# GrowthBook
+export GROWTHBOOK_CLIENT_KEY="some random key"

package.json

@@ -29,6 +29,7 @@
     "@aws-sdk/client-dynamodb": "^3.370.0",
     "@aws-sdk/client-secrets-manager": "^3.370.0",
     "@aws-sdk/lib-dynamodb": "^3.370.0",
+    "@growthbook/growthbook": "^0.27.0",
     "@octokit/rest": "^18.12.0",
     "@opengovsg/formsg-sdk": "^0.10.0",
     "@opengovsg/sgid-client": "^2.0.0",
@@ -47,9 +48,11 @@
     "convict": "^6.2.4",
     "cookie-parser": "~1.4.5",
     "cors": "^2.8.5",
+    "cross-fetch": "^4.0.0",
     "crypto-js": "^4.1.1",
     "dd-trace": "^4.7.0",
     "debug": "~2.6.9",
+    "eventsource": "^2.0.2",
     "exponential-backoff": "^3.1.0",
     "express": "~4.17.3",
     "express-rate-limit": "^6.7.0",

src/classes/UserWithSiteSessionData.ts

@@ -1,7 +1,12 @@
+import { GrowthBook } from "@growthbook/growthbook"
+
+import { FeatureFlags } from "@root/types/featureFlags"
+
 import UserSessionData, { SessionDataProps } from "./UserSessionData"
 
 export type UserWithSiteSessionDataProps = SessionDataProps & {
   siteName: string
+  growthbook?: GrowthBook
 }
 
 /**
@@ -11,9 +16,14 @@ export type UserWithSiteSessionDataProps = SessionDataProps & {
 class UserWithSiteSessionData extends UserSessionData {
   readonly siteName: string
 
+  readonly growthbook?: GrowthBook<FeatureFlags>
+
   constructor(props: UserWithSiteSessionDataProps) {
     super(props)
     this.siteName = props.siteName
+    if (props.growthbook) {
+      this.growthbook = props.growthbook
+    }
   }
 
   getGithubParamsWithSite() {

src/config/config.ts

@@ -405,13 +405,15 @@ const config = convict({
       default: "mock-redirect-uri",
     },
   },
-  featureFlags: {
-    ggsWhitelistedRepos: {
-      doc: "Comma-separated list of whitelisted repos for local Git service",
-      env: "WHITELISTED_GIT_SERVICE_REPOS",
-      format: String,
+  growthbook: {
+    clientKey: {
+      doc: "GrowthBook SDK client key",
+      env: "GROWTHBOOK_CLIENT_KEY",
+      format: "required-string",
       default: "",
     },
+  },
+  featureFlags: {
     ggsTrackedSites: {
       doc: "Comma-separated list of tracked sites for GitHub API hits",
       env: "GGS_EXPERIMENTAL_TRACKING_SITES",

src/constants/featureFlags.ts

@@ -0,0 +1,3 @@
+export const FEATURE_FLAGS = {
+  GGS_WHITELISTED_REPOS: "ggs_whitelisted_repos",
+} as const

src/constants/index.ts

@@ -1,3 +1,4 @@
 export * from "./constants"
 export * from "./pages"
 export * from "./versions"
+export * from "./featureFlags"

src/fixtures/sessionData.ts

@@ -1,6 +1,9 @@
+import { GrowthBook } from "@growthbook/growthbook"
+
 import GithubSessionData from "@root/classes/GithubSessionData"
 import UserSessionData from "@root/classes/UserSessionData"
 import UserWithSiteSessionData from "@root/classes/UserWithSiteSessionData"
+import { FeatureFlags } from "@root/types/featureFlags"
 
 import {
   MOCK_USER_EMAIL_ONE,
@@ -20,6 +23,7 @@ export const mockEmail = "mockEmail"
 export const mockTreeSha = "mockTreeSha"
 export const mockCurrentCommitSha = "mockCurrentCommitSha"
 export const mockSiteName = "mockSiteName"
+export const mockGrowthBook = new GrowthBook<FeatureFlags>()
 
 export const mockGithubState = {
   treeSha: mockTreeSha,
@@ -41,6 +45,17 @@ export const mockUserWithSiteSessionData = new UserWithSiteSessionData({
   siteName: mockSiteName,
 })
 
+export const mockUserWithSiteSessionDataAndGrowthBook = new UserWithSiteSessionData(
+  {
+    githubId: mockGithubId,
+    accessToken: mockAccessToken,
+    isomerUserId: mockIsomerUserId,
+    email: mockEmail,
+    siteName: mockSiteName,
+    growthbook: mockGrowthBook,
+  }
+)
+
 export const mockGithubSessionData = new GithubSessionData({
   treeSha: mockTreeSha,
   currentCommitSha: mockCurrentCommitSha,

src/middleware/authentication.ts

@@ -1,12 +1,14 @@
 import autoBind from "auto-bind"
-import { NextFunction, Request, Response } from "express"
+import { NextFunction, Response } from "express"
 import { Session } from "express-session"
 
 import UserSessionData from "@root/classes/UserSessionData"
 import AuthenticationMiddlewareService from "@root/services/middlewareServices/AuthenticationMiddlewareService"
 import { SessionData } from "@root/types/express/session"
+import { GrowthBookAttributes } from "@root/types/featureFlags"
+import { RequestWithGrowthBook } from "@root/types/request"
 
-interface RequestWithSession extends Request {
+interface RequestWithSession extends RequestWithGrowthBook {
   session: Session & SessionData
 }
 
@@ -30,6 +32,7 @@ export class AuthenticationMiddleware {
     next: NextFunction
   ) {
     const { cookies, originalUrl: url, session } = req
+
     try {
       const {
         isomerUserId,
@@ -46,6 +49,19 @@ export class AuthenticationMiddleware {
         ...rest,
       })
       res.locals.userSessionData = userSessionData
+
+      // populate growthbook
+      if (req.growthbook) {
+        const gbAttributes: GrowthBookAttributes = {
+          isomerUserId,
+          email,
+        }
+        if (session.userInfo.githubId) {
+          gbAttributes.githubId = session.userInfo.githubId
+        }
+        req.growthbook.setAttributes(gbAttributes)
+      }
+
       return next()
     } catch (err) {
       return next(err)

src/middleware/featureFlag.ts

@@ -0,0 +1,31 @@
+import UserWithSiteSessionData from "@root/classes/UserWithSiteSessionData"
+import config from "@root/config/config"
+import logger from "@root/logger/logger"
+import { RequestHandlerWithGrowthbook } from "@root/types"
+import { getNewGrowthbookInstance } from "@root/utils/growthbook-utils"
+
+export const featureFlagMiddleware: RequestHandlerWithGrowthbook<
+  never,
+  unknown,
+  unknown,
+  never,
+  { userWithSiteSessionData: UserWithSiteSessionData }
+> = async (req, res, next) => {
+  req.growthbook = getNewGrowthbookInstance(config.get("growthbook.clientKey"))
+
+  // Clean up at the end of the request
+  res.on("close", () => {
+    if (req.growthbook) req.growthbook.destroy()
+  })
+
+  // Wait for features to load (will be cached in-memory for future requests)
+  req.growthbook
+    .loadFeatures({ autoRefresh: true })
+    .then(() => next())
+    .catch((e: unknown) => {
+      logger.error(
+        `Failed to load features from GrowthBook: ${JSON.stringify(e)}`
+      )
+      next()
+    })
+}

src/middleware/index.ts

@@ -9,13 +9,16 @@ import UserWithSiteSessionData from "@classes/UserWithSiteSessionData"
 
 import CollaboratorsService from "@root/services/identity/CollaboratorsService"
 import { RequestHandler } from "@root/types"
+import { GrowthBookAttributes } from "@root/types/featureFlags"
 import IdentityAuthService from "@services/identity/AuthService"
 import IsomerAdminsService from "@services/identity/IsomerAdminsService"
 import UsersService from "@services/identity/UsersService"
 import AuthenticationMiddlewareService from "@services/middlewareServices/AuthenticationMiddlewareService"
 import AuthorizationMiddlewareService from "@services/middlewareServices/AuthorizationMiddlewareService"
 import FormsProcessingService from "@services/middlewareServices/FormsProcessingService"
 
+import { featureFlagMiddleware } from "./featureFlag"
+
 const getAuthenticationMiddleware = () => {
   const authenticationMiddlewareService = new AuthenticationMiddlewareService()
   const authenticationMiddleware = new AuthenticationMiddleware({
@@ -82,11 +85,26 @@ const attachSiteHandler: RequestHandler<
     params: { siteName },
   } = req
   const { userSessionData } = res.locals
+
+  // populate growthbook
+  if (req.growthbook) {
+    const { isomerUserId, email, githubId } = userSessionData
+    const gbAttributes: GrowthBookAttributes = {
+      isomerUserId,
+      email,
+      siteName,
+    }
+    if (githubId) gbAttributes.githubId = githubId
+    req.growthbook.setAttributes(gbAttributes)
+  }
+
   const userWithSiteSessionData = new UserWithSiteSessionData({
     ...userSessionData.getGithubParams(),
     siteName,
+    growthbook: req.growthbook, // inject into session
   })
   res.locals.userWithSiteSessionData = userWithSiteSessionData
+
   return next()
 }
 
@@ -95,4 +113,5 @@ export {
   getAuthorizationMiddleware,
   attachFormSGHandler,
   attachSiteHandler,
+  featureFlagMiddleware,
 }