feat(axios): implement etag functionality (#765)

* chore(axios): upgrade axios to 0.24 and add axios cache interceptor

pin axios to only allow minor patch upgrades, and pin the version of interceptor exactly. this is
because there is a support table
[here](https://axios-cache-interceptor.js.org/guide/getting-started) that lists the compat and we
require at least 0.6.x for ETag support. in order to prevent versioning errors (0.8.4 of interceptor
works wtih 0.25 of axios!!), we will pin the exact version of interceptor + patch version of axios

* feat(axiosinstance): add initialisation code

* chore(package): lock versions

* fix(axiosinstance): update config for cache interceptor

package.json

@@ -34,7 +34,8 @@
     "auto-bind": "^4.0.0",
     "aws-lambda": "^1.0.7",
     "aws-sdk": "^2.946.0",
-    "axios": "^0.21.3",
+    "axios": "~0.25.0",
+    "axios-cache-interceptor": "^0.9.2",
     "base-64": "^0.1.0",
     "bcrypt": "^5.1.0",
     "bluebird": "^3.7.2",

src/services/api/AxiosInstance.ts

@@ -1,4 +1,5 @@
 import axios, { AxiosRequestConfig, AxiosResponse } from "axios"
+import { setupCache } from "axios-cache-interceptor"
 
 import { config } from "@config/config"
 
@@ -10,10 +11,10 @@ import tracer from "@utils/tracer"
 // Env vars
 const GITHUB_ORG_NAME = config.get("github.orgName")
 
-const requestFormatter = async (config: AxiosRequestConfig) => {
+const requestFormatter = async (axiosConfig: AxiosRequestConfig) => {
   logger.info("Making GitHub API call")
 
-  const authMessage = config.headers.Authorization
+  const authMessage = axiosConfig.headers?.Authorization
 
   // If accessToken is missing, authMessage is `token `
   // NOTE: This also implies that the user has not provided
@@ -25,15 +26,17 @@ const requestFormatter = async (config: AxiosRequestConfig) => {
 
   if (isEmailLoginUser) {
     const accessToken = await getAccessToken()
-    config.headers.Authorization = `token ${accessToken}`
+    axiosConfig.headers = {
+      Authorization: `token ${accessToken}`,
+    }
     tracer.use("http", {
       hooks: {
         request: (span, req, res) => {
           span?.setTag("user.type", "email")
         },
       },
     })
-    logger.info(`Email login user made call to Github API: ${config.url}`)
+    logger.info(`Email login user made call to Github API: ${axiosConfig.url}`)
   } else {
     tracer.use("http", {
       hooks: {
@@ -42,21 +45,25 @@ const requestFormatter = async (config: AxiosRequestConfig) => {
         },
       },
     })
-    logger.info(`Github login user made call to Github API: ${config.url}`)
+    logger.info(`Github login user made call to Github API: ${axiosConfig.url}`)
   }
   return {
-    ...config,
+    ...axiosConfig,
     headers: {
       "Content-Type": "application/json",
-      ...config.headers,
+      ...axiosConfig.headers,
     },
   }
 }
 
 const respHandler = (response: AxiosResponse) => {
   // Any status code that lie within the range of 2xx will cause this function to trigger
   const GITHUB_API_LIMIT = 5000
-  const remainingRequests = response.headers["x-ratelimit-remaining"]
+  const remainingRequests =
+    // NOTE: This raises an alarm if the header is missing
+    // or if the header is not a number.
+    // This is because the header should always be present.
+    parseInt(response.headers["x-ratelimit-remaining"], 10) || 0
   if (remainingRequests < GITHUB_API_LIMIT * 0.2) {
     logger.info("80% of access token capacity reached")
   } else if (remainingRequests < GITHUB_API_LIMIT * 0.4) {
@@ -65,9 +72,15 @@ const respHandler = (response: AxiosResponse) => {
   return response
 }
 
-const isomerRepoAxiosInstance = axios.create({
-  baseURL: `https://api.github.com/repos/${GITHUB_ORG_NAME}/`,
-})
+const isomerRepoAxiosInstance = setupCache(
+  axios.create({
+    baseURL: `https://api.github.com/repos/${GITHUB_ORG_NAME}/`,
+  }),
+  {
+    interpretHeader: true,
+    etag: true,
+  }
+)
 isomerRepoAxiosInstance.interceptors.request.use(requestFormatter)
 isomerRepoAxiosInstance.interceptors.response.use(respHandler)