Axios Interceptors retry original request and access original promise

I have an interceptor in place to catch 401 errors if the access token expires. If it expires it tries the refresh token to get a new access token. If any other calls are made during this time they are queued until the access token is validated.

This is all working very well. However when processing the queue using Axios(originalRequest) the originally attached promises are not being called. See below for an example.

Working interceptor code:

Axios.interceptors.response.use(
  response => response,
  (error) => {
    const status = error.response ? error.response.status : null
    const originalRequest = error.config

    if (status === 401) {
      if (!store.state.auth.isRefreshing) {
        store.dispatch('auth/refresh')
      }

      const retryOrigReq = store.dispatch('auth/subscribe', token => {
        originalRequest.headers['Authorization'] = 'Bearer ' + token
        Axios(originalRequest)
      })

      return retryOrigReq
    } else {
      return Promise.reject(error)
    }
  }
)

Refresh Method (Used the refresh token to get a new access token)

refresh ({ commit }) {
  commit(types.REFRESHING, true)
  Vue.$http.post('/login/refresh', {
    refresh_token: store.getters['auth/refreshToken']
  }).then(response => {
    if (response.status === 401) {
      store.dispatch('auth/reset')
      store.dispatch('app/error', 'You have been logged out.')
    } else {
      commit(types.AUTH, {
        access_token: response.data.access_token,
        refresh_token: response.data.refresh_token
      })
      store.dispatch('auth/refreshed', response.data.access_token)
    }
  }).catch(() => {
    store.dispatch('auth/reset')
    store.dispatch('app/error', 'You have been logged out.')
  })
},

Subscribe method in auth/actions module:

subscribe ({ commit }, request) {
  commit(types.SUBSCRIBEREFRESH, request)
  return request
},

As well as the Mutation:

[SUBSCRIBEREFRESH] (state, request) {
  state.refreshSubscribers.push(request)
},

Here is a sample action:

Vue.$http.get('/users/' + rootState.auth.user.id + '/tasks').then(response => {
  if (response && response.data) {
    commit(types.NOTIFICATIONS, response.data || [])
  }
})

If this request was added to the queue I because the refresh token had to access a new token I would like to attach the original then():

  const retryOrigReq = store.dispatch('auth/subscribe', token => {
    originalRequest.headers['Authorization'] = 'Bearer ' + token
    // I would like to attache the original .then() as it contained critical functions to be called after the request was completed. Usually mutating a store etc...
    Axios(originalRequest).then(//if then present attache here)
  })

Once the access token has been refreshed the queue of requests is processed:

refreshed ({ commit }, token) {
  commit(types.REFRESHING, false)
  store.state.auth.refreshSubscribers.map(cb => cb(token))
  commit(types.CLEARSUBSCRIBERS)
},

Update Feb 13, 2019

As many people have been showing an interest in this topic, I've created the axios-auth-refresh package which should help you to achieve behaviour specified here.

---

The key here is to return the correct Promise object, so you can use .then() for chaining. We can use Vuex's state for that. If the refresh call happens, we can not only set the refreshing state to true, we can also set the refreshing call to the one that's pending. This way using .then() will always be bound onto the right Promise object, and be executed when the Promise is done. Doing it so will ensure you don't need an extra queue for keeping the calls which are waiting for the token's refresh.

function refreshToken(store) {
    if (store.state.auth.isRefreshing) {
        return store.state.auth.refreshingCall;
    }
    store.commit('auth/setRefreshingState', true);
    const refreshingCall = Axios.get('get token').then(({ data: { token } }) => {
        store.commit('auth/setToken', token)
        store.commit('auth/setRefreshingState', false);
        store.commit('auth/setRefreshingCall', undefined);
        return Promise.resolve(true);
    });
    store.commit('auth/setRefreshingCall', refreshingCall);
    return refreshingCall;
}

This would always return either already created request as a Promise or create the new one and save it for the other calls. Now your interceptor would look similar to the following one.

Axios.interceptors.response.use(response => response, error => {
    const status = error.response ? error.response.status : null

    if (status === 401) {
        
        return refreshToken(store).then(_ => {
            error.config.headers['Authorization'] = 'Bearer ' + store.state.auth.token;
            error.config.baseURL = undefined;
            return Axios.request(error.config);
        });
    }

    return Promise.reject(error);
});

This will allow you to execute all the pending requests once again. But all at once, without any querying.

---

If you want the pending requests to be executed in the order they were actually called, you need to pass the callback as a second parameter to the refreshToken() function, like so.

function refreshToken(store, cb) {
    if (store.state.auth.isRefreshing) {
        const chained = store.state.auth.refreshingCall.then(cb);
        store.commit('auth/setRefreshingCall', chained);
        return chained;
    }
    store.commit('auth/setRefreshingState', true);
    const refreshingCall = Axios.get('get token').then(({ data: { token } }) => {
        store.commit('auth/setToken', token)
        store.commit('auth/setRefreshingState', false);
        store.commit('auth/setRefreshingCall', undefined);
        return Promise.resolve(token);
    }).then(cb);
    store.commit('auth/setRefreshingCall', refreshingCall);
    return refreshingCall;
}

And the interceptor:

Axios.interceptors.response.use(response => response, error => {
    const status = error.response ? error.response.status : null

    if (status === 401) {
        
        return refreshToken(store, _ => {
            error.config.headers['Authorization'] = 'Bearer ' + store.state.auth.token;
            error.config.baseURL = undefined;
            return Axios.request(error.config);
        });
    }

    return Promise.reject(error);
});

I haven't tested the second example, but it should work or at least give you an idea.

Working demo of first example - because of the mock requests and demo version of service used for them, it will not work after some time, still, the code is there.

Source: Interceptors - how to prevent intercepted messages to resolve as an error

This could be done with a single interceptor:

let _refreshToken = '';
let _authorizing: Promise<void> | null = null;
const HEADER_NAME = 'Authorization';

axios.interceptors.response.use(undefined, async (error: AxiosError) => {
    if(error.response?.status !== 401) {
        return Promise.reject(error);
    }

    // create pending authorization
    _authorizing ??= (_refreshToken ? refresh : authorize)()
        .finally(() => _authorizing = null)
        .catch(error => Promise.reject(error));

    const originalRequestConfig = error.config;
    delete originalRequestConfig.headers[HEADER_NAME]; // use from defaults

    // delay original requests until authorization has been completed
    return _authorizing.then(() => axios.request(originalRequestConfig));
});

The rest is an application specific code:

• Login to api
• Save/load auth data to/from storage
• Refresh token

Check out the complete example.

Why not try something like this ?

Here I use AXIOS interceptors in both directions. For the outgoing direction I set the Authorization header. For the incoming direction - if there is an error, I return a promise (and AXIOS will try to resolve it). The promise checks what the error was - if it was 401 and we see it for the first time (i.e. we are not inside the retry) then I try to refresh the token. Otherwise I throw the original error. In my case refreshToken() uses AWS Cognito but you can use whatever suits you most. Here I have 2 callbacks for refreshToken():

1. when the token is successfully refreshed, I retry the AXIOS request using an updated config - including the new fresh token and setting a retry flag so that we do not enter an endless cycle if the API repeatedly responds with 401 errors. We need to pass the resolve and reject arguments to AXIOS or otherwise our fresh new promise will be never resolved/rejected.

2. if the token could not be refreshed for any reason - we reject the promise. We can not simply throw an error because there might be try/catch block around the callback inside AWS Cognito

---

Vue.prototype.$axios = axios.create(
  {
    headers:
      {
        'Content-Type': 'application/json',
      },
    baseURL: process.env.API_URL
  }
);

Vue.prototype.$axios.interceptors.request.use(
  config =>
  {
    events.$emit('show_spin');
    let token = getTokenID();
    if(token && token.length) config.headers['Authorization'] = token;
    return config;
  },
  error =>
  {
    events.$emit('hide_spin');
    if (error.status === 401) VueRouter.push('/login'); // probably not needed
    else throw error;
  }
);

Vue.prototype.$axios.interceptors.response.use(
  response =>
  {
    events.$emit('hide_spin');
    return response;
  },
  error =>
  {
    events.$emit('hide_spin');
    return new Promise(function(resolve,reject)
    {
      if (error.config && error.response && error.response.status === 401 && !error.config.__isRetry)
      {
        myVue.refreshToken(function()
        {
          error.config.__isRetry = true;
          error.config.headers['Authorization'] = getTokenID();
          myVue.$axios(error.config).then(resolve,reject);
        },function(flag) // true = invalid session, false = something else
        {
          if(process.env.NODE_ENV === 'development') console.log('Could not refresh token');
          if(getUserID()) myVue.showFailed('Could not refresh the Authorization Token');
          reject(flag);
        });
      }
      else throw error;
    });
  }
);