How to execute an async fetch request and then retry last failed request? - apollo

Question

Apollo link offers an error handler onError
Issue:
Currently, we wish to refresh oauth tokens when they expires during an apollo call and we are unable to execute an async fetch request inside the onError properly.
Code:
initApolloClient.js
import { ApolloClient } from 'apollo-client';
import { onError } from 'apollo-link-error';
import { ApolloLink, fromPromise } from 'apollo-link';
//Define Http link
const httpLink = new createHttpLink({
uri: '/my-graphql-endpoint',
credentials: 'include'
});
//Add on error handler for apollo link
return new ApolloClient({
link: ApolloLink.from([
onError(({ graphQLErrors, networkError, operation, forward }) => {
if (graphQLErrors) {
//User access token has expired
if(graphQLErrors[0].message==="Unauthorized") {
//We assume we have both tokens needed to run the async request
if(refreshToken && clientToken) {
//let's refresh token through async request
return fromPromise(
authAPI.requestRefreshToken(refreshToken,clientToken)
.then((refreshResponse) => {
let headers = {
//readd old headers
...operation.getContext().headers,
//switch out old access token for new one
authorization: `Bearer ${refreshResponse.access_token}`,
};
operation.setContext({
headers
});
//Retry last failed request
return forward(operation);
})
.catch(function (error) {
//No refresh or client token available, we force user to login
return error;
})
)
}
}
}
}
}
}),
What happens is:
Initial graphQL query runs and fails due to unauthorization
The onError function of ApolloLink is executed.
The promise to refresh the token is executed.
The onError function of ApolloLink is executed again??
The promise to refresh the token is completed.
The initial graphQL query result is returned and its data is undefined
Between step 5 and 6, apollo doesn't re-run the initial failed graphQL query and hence the result is undefined.
Errors from console:
Uncaught (in promise) Error: Network error: Error writing result to store for query:
query UserProfile($id: ID!) {
UserProfile(id: $id) {
id
email
first_name
last_name
}
__typename
}
}
The solution should allow us to:
Run an async request when an operation fails
Wait for the result of the request
Retry failed operation with data from the request's result
Operation should succeed to return its intended result

Answer 1

I'm refreshing the token this way (updated OP's):
import { ApolloClient } from 'apollo-client';
import { onError } from 'apollo-link-error';
import { ApolloLink, Observable } from 'apollo-link'; // add Observable
// Define Http link
const httpLink = new createHttpLink({
uri: '/my-graphql-endpoint',
credentials: 'include'
});
// Add on error handler for apollo link
return new ApolloClient({
link: ApolloLink.from([
onError(({ graphQLErrors, networkError, operation, forward }) => {
// User access token has expired
if (graphQLErrors && graphQLErrors[0].message === 'Unauthorized') {
// We assume we have both tokens needed to run the async request
if (refreshToken && clientToken) {
// Let's refresh token through async request
return new Observable(observer => {
authAPI.requestRefreshToken(refreshToken, clientToken)
.then(refreshResponse => {
operation.setContext(({ headers = {} }) => ({
headers: {
// Re-add old headers
...headers,
// Switch out old access token for new one
authorization: `Bearer ${refreshResponse.access_token}` || null,
}
}));
})
.then(() => {
const subscriber = {
next: observer.next.bind(observer),
error: observer.error.bind(observer),
complete: observer.complete.bind(observer)
};
// Retry last failed request
forward(operation).subscribe(subscriber);
})
.catch(error => {
// No refresh or client token available, we force user to login
observer.error(error);
});
});
}
}
})
])
});

Answer 2

Accepted answer is quite good but it wouldn't work with 2 or more concurrent requests. I've crafted the one below after testing different cases with my token renew workflow that fits my needs.
It's necessary to set errorLink before authLink in link pipeline.
client.ts
import { ApolloClient, from, HttpLink } from '#apollo/client'
import errorLink from './errorLink'
import authLink from './authLink'
import cache from './cache'
const httpLink = new HttpLink({
uri: process.env.REACT_APP_API_URL,
})
const apiClient = new ApolloClient({
link: from([errorLink, authLink, httpLink]),
cache,
credentials: 'include',
})
export default apiClient
Cache shared between 2 apollo client instances for setting user query when my renewal token is expired
cache.ts
import { InMemoryCache } from '#apollo/client'
const cache = new InMemoryCache()
export default cache
authLink.ts
import { ApolloLink } from '#apollo/client'
type Headers = {
authorization?: string
}
const authLink = new ApolloLink((operation, forward) => {
const accessToken = localStorage.getItem('accessToken')
operation.setContext(({ headers }: { headers: Headers }) => ({
headers: {
...headers,
authorization: accessToken,
},
}))
return forward(operation)
})
export default authLink
errorLink.ts
import { ApolloClient, createHttpLink, fromPromise } from '#apollo/client'
import { onError } from '#apollo/client/link/error'
import { GET_CURRENT_USER } from 'queries'
import { RENEW_TOKEN } from 'mutations'
import cache from './cache'
let isRefreshing = false
let pendingRequests: Function[] = []
const setIsRefreshing = (value: boolean) => {
isRefreshing = value
}
const addPendingRequest = (pendingRequest: Function) => {
pendingRequests.push(pendingRequest)
}
const renewTokenApiClient = new ApolloClient({
link: createHttpLink({ uri: process.env.REACT_APP_API_URL }),
cache,
credentials: 'include',
})
const resolvePendingRequests = () => {
pendingRequests.map((callback) => callback())
pendingRequests = []
}
const getNewToken = async () => {
const oldRenewalToken = localStorage.getItem('renewalToken')
const {
data: {
renewToken: {
session: { renewalToken, accessToken },
},
},
} = await renewTokenApiClient.mutate({
mutation: RENEW_TOKEN,
variables: { input: { renewalToken: oldRenewalToken } },
})!
localStorage.setItem('renewalToken', renewalToken)
localStorage.setItem('accessToken', accessToken)
}
const errorLink = onError(({ graphQLErrors, operation, forward }) => {
if (graphQLErrors) {
for (const err of graphQLErrors) {
switch (err?.message) {
case 'expired':
if (!isRefreshing) {
setIsRefreshing(true)
return fromPromise(
getNewToken().catch(() => {
resolvePendingRequests()
setIsRefreshing(false)
localStorage.clear()
// Cache shared with main client instance
renewTokenApiClient!.writeQuery({
query: GET_CURRENT_USER,
data: { currentUser: null },
})
return forward(operation)
}),
).flatMap(() => {
resolvePendingRequests()
setIsRefreshing(false)
return forward(operation)
})
} else {
return fromPromise(
new Promise((resolve) => {
addPendingRequest(() => resolve())
}),
).flatMap(() => {
return forward(operation)
})
}
}
}
}
})
export default errorLink

Answer 3

We just had the same issues and after a very complicated solution with lots of Observeables we got a simple solution using promises which will be wrapped as an Observable in the end.
let tokenRefreshPromise: Promise = Promise.resolve()
let isRefreshing: boolean
function createErrorLink (store): ApolloLink {
return onError(({ graphQLErrors, networkError, operation, forward }) => {
if (graphQLErrors) {
// this is a helper method where we are checking the error message
if (isExpiredLogin(graphQLErrors) && !isRefreshing) {
isRefreshing = true
tokenRefreshPromise = store.dispatch('authentication/refreshToken')
tokenRefreshPromise.then(() => isRefreshing = false)
}
return fromPromise(tokenRefreshPromise).flatMap(() => forward(operation))
}
if (networkError) {
handleNetworkError(displayErrorMessage)
}
})
}
All pending requests are waiting for the tokenRefreshPromise and will then be forwarded.