I am trying to set up a basic express app to get some API data using axios. I want to do things the right way but I am a bit lost with error handling. Ideally, if there is an error I want to communicate it to users which I could do if the API call was within it the route. But how do you do it if it's a separate function?
axios call function using async:
const getForm = async () => {
try {
const config = {
method: 'get',
url: 'https://api.something.org/niceform'
}
}
const response = await axios(config)
return response
} catch (error) {
return error.message
}
}
express route:
app.get('/niceform', async (req, res) => {
try {
const data = await getForm()
res.send(data)
} catch (error) {
???
}
})
If I understand it correctly the getForm() function will return either the response or the error and then the route will send whatever comes back. But then what does the route's catch block do and how should I use it?
Is this setup considered to be a good practice?
Any advice would be appreciated, I am still learning.
The catch block can be removed from the getForm function. An error will be caught anyways in the get route.
const getForm = async () => {
const config = {
method: 'get',
url: 'https://api.something.org/niceform'
};
const response = await axios(config);
return response;
}
Or the error can be caught inside getForm, in order to do something in that catch block, and be thrown:
const getForm = async () => {
const config = {
method: 'get',
url: 'https://api.something.org/niceform'
};
try {
const response = await axios(config);
return response;
} catch (err) {
// log the error
// add extra information to the error
// else
// (see the attached answer)
throw err;
}
}
Consequently, in the catch block in the get route, an error can be responded:
app.get('/niceform', async (req, res) => {
try {
const data = await getForm();
res.send(data);
} catch (error) {
res.error(error);
}
})
Reference:
https://stackoverflow.com/a/42171508/3563737
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/throw
Related
I have a react native project in which I'm calling some API's using redux-saga mechanism. Now when I added response interceptor for axios my saga api's are not working anymore. Does any knows how I can fix this?
here is the code for my axios instance class and response interceptor
const getLoggedInUser = async () => {
const savedUser = JSON.parse(
await getDataFromAsyncStorage(APP_CONSTANTS.SAVED_USER)
)
if (savedUser?.user_id != null) {
return savedUser
}
return null
}
const baseapi = axios.create({
baseURL: APP_CONSTANTS.BASE_URL,
headers: {},
})
baseapi.interceptors.request.use(
async (config) => {
const token = await getLoggedInUser()
const userId = token?.user_id
const authToken = token?.token
if (token) {
baseapi.defaults.headers.common['userId'] = token
baseapi.defaults.headers.common['token'] = authToken
}
return config
},
(error) => {
return Promise.reject(error)
}
)
// Response interceptor for API calls
baseapi.interceptors.response.use(
(response) => {
return response
},
async function (error) {
const originalRequest = error.config
if (error.response.status === 403 /* && !originalRequest._retry */) {
return baseapi(originalRequest)
}
return Promise.reject(error)
}
)
This is my saga class code and it fails directly when I add a response interceptor
function* getTopicList(action) {
try {
yield put({type: ACTION_TYPES.START_TOPIC_LIST})
const {payload} = action
const res = yield call(getAllTopicsOfBatch, payload)
if (res?.status == APP_CONSTANTS.SUCCESS_STATUS) {
yield put({
type: ACTION_TYPES.SET_TOPIC_LIST,
payload: {data: res?.data?.topics},
})
} else {
alert('OOPS Something went wrong! Please try again')
yield put({
type: ACTION_TYPES.ERROR_TOPIC_LIST,
payload: 'Something Went Wrong Please Try Again',
})
}
} catch (error) {
console.log('RESPONES error', error)
alert('OOPS Something went wrong! Please try again')
yield put({
type: ACTION_TYPES.ERROR_TOPIC_LIST,
payload: 'Something Went Wrong Please Try Again',
})
}
}
The code looks mostly fine, the only two things I found that are likely causing problems are:
In the request interceptors you are likely wrongly passing the whole token as userId instead of userId
baseapi.defaults.headers.common['userId'] = token // 'token' should be 'userId'
In the response interceptors error handler, you are not guaranteed to have 'response' property on error.
if (error.response.status === 403) // use error?.response
If neither of these things will fix your problem my guess is you have a problem in your endpoint and so you should examine the response errors you get to guide you.
Sending a logout request to my server but I'm never getting a reply. The logout function is being called and the userID key is being deleted from my redis cache but I never get a response. Here's my code.
export const logout = async (req, res) => {
console.log("logout called");
const { userID } = req.user;
client.del(userID.toString, (err, reply) => {
console.log("inside client.del");
if (err) {
return res.status(500);
} else {
return res.status(200);
}
});
};
Because of callback, you should use promise
export const logout = async (req, res) => {
return new Promise((resolve,reject) => {
console.log("logout called");
const { userID } = req.user;
client.del(userID.toString, (err, reply) => {
console.log("inside client.del");
if (err) {
reject(res.status(500));
} else {
resolve(res.status(200));
}
});
});
}
res.status() does not send a response from the server. All it does is set the status as a property on the response object that will go with some future call that actually sends the response.
It is meant to be used in something like this:
res.status(500).send("Database error");
If you look at the Express doc for res.status(), you will see these examples:
res.status(403).end()
res.status(400).send('Bad Request')
res.status(404).sendFile('/absolute/path/to/404.png')
And, see that they all are followed by some other method that actually causes the response to be sent.
And, if you still had any doubt, you can look in the Express code repository and see this:
res.status = function status(code) {
this.statusCode = code;
return this;
};
Which shows that it's just setting a property on the response object and not actually sending the response yet.
You can use res.sendStatus() instead which will BOTH set the status and send the response:
export const logout = (req, res) => {
console.log("logout called");
const { userID } = req.user;
client.del(userID.toString, (err, reply) => {
console.log("inside client.del");
if (err) {
res.sendStatus(500);
} else {
res.sendStatus(200);
}
});
};
Note, I removed the two return keywords since they don't accomplish anything useful in this particular context.
I also removed the async keyword from the function definition since it was not doing anything useful in this context.
I know some questions about the subject has been opened here and there, but my issue is different :
all the other ones appear in dev mode, in my case it's in production,
a very big percentage of requests pass, a few of them is TypeError: Network request failed - but sometimes for critical requests
it's random, not always the same request. Sometimes it passes, sometimes not.
it appears to three on my projects, one is on AWS the other one on Clever-Cloud, both are projects between 1000 and 5000 users, servers are quite too big for what they do - I think I removed the risk of a server fault. Even if... I can reproduce locally when I don't start the api locally. So it's like the api is not responding, but as I said, I don't think so.
I have no clue where to dig anymore...
I can give you my API.js service file, maybe you'll find what's wrong ?
import URI from 'urijs';
import { Platform } from 'react-native';
import NetInfo from '#react-native-community/netinfo';
import { getUserToken, wipeData } from '../utils/data';
import { SCHEME, MW_API_HOST } from '../config';
import deviceInfoModule from 'react-native-device-info';
import { capture } from '../utils/sentry';
const unauthorisedHandler = (navigation) => {
wipeData();
navigation.reset({ index: 0, routes: [{ name: 'Auth' }] });
};
const checkNetwork = async (test = false) => {
const isConnected = await NetInfo.fetch().then((state) => state.isConnected);
if (!isConnected || test) {
await new Promise((res) => setTimeout(res, 1500));
return false;
}
return true;
};
class ApiService {
host = MW_API_HOST;
scheme = SCHEME;
getUrl = (path, query) => {
return new URI().host(this.host).scheme(this.scheme).path(path).setSearch(query).toString();
};
execute = async ({ method = 'GET', path = '', query = {}, headers = {}, body = null }) => {
try {
const config = {
method,
headers: {
'Content-Type': 'application/json',
Accept: 'application/json',
appversion: deviceInfoModule.getBuildNumber(),
appdevice: Platform.OS,
currentroute: this.navigation?.getCurrentRoute?.()?.name,
...headers,
},
body: body ? JSON.stringify(body) : null,
};
const url = this.getUrl(path, query);
console.log('url: ', url);
const canFetch = await checkNetwork();
if (!canFetch) return;
let response;
// To try to avoid mysterious `TypeError: Network request failed` error
// that throws an error directly
// we try catch and try one more time.
try {
response = await fetch(url, config);
} catch (e) {
if (e?.toString().includes('Network request failed')) {
// try again
await new Promise((res) => setTimeout(res, 250));
console.log('try again because Network request failed');
response = await fetch(url, config);
} else {
throw e;
}
}
if (!response.ok) {
if (response.status === 401) {
const token = await getUserToken();
if (token) unauthorisedHandler(API.navigation);
return response;
}
}
if (response.json) return await response.json();
return response;
} catch (e) {
capture(e, { extra: { method, path, query, headers, body } });
return { ok: false, error: "Sorry, an error occured, technical team has been warned." };
}
};
executeWithToken = async ({ method = 'GET', path = '', query = {}, headers = {}, body = null }) => {
const token = await getUserToken();
if (token) headers.Authorization = token;
return this.execute({ method, path, query, headers, body });
};
get = async (args) => this.executeWithToken({ method: 'GET', ...args });
post = async (args) => this.executeWithToken({ method: 'POST', ...args });
put = async (args) => this.executeWithToken({ method: 'PUT', ...args });
delete = async (args) => this.executeWithToken({ method: 'DELETE', ...args });
}
const API = new ApiService();
export default API;
Talking with experts here and there, it seems that it's normal : internet network is not 100% reliable, so sometimes, request fail, for a reason that we can't anticipate (tunnel, whatever).
I ended up using fetch-retry and I still have a few of those, but much less !
I tried using redux to save token the one I get from api in react native ..its working now.
First one is for settoken and other one is for gettoken.
enter image description here
export const verifyOTP = (formValues, actions) => {
return async (dispatch) => {
dispatch(startSubmitting());
const url = `/validate-otp`;
var formdata = new FormData();
formdata.append("mobile", formValues.mobile);
formdata.append("otp", formValues.otp);
const response = await api.post(url, formdata);
dispatch({
type: "VERIFY_OTP",
payload: response,
});
dispatch(stopSubmitting());
await SecureStore.setItemAsync("userToken", response.data.access_token);
};
};
export const checkUser = () => {
return async (dispatch) => {
const token = await SecureStore.getItemAsync("userToken");
const url = `/me`;
const response = await api
.post(url, { token })
.then((res) => {
return res;
})
.catch((error) => {
return error.response;
});
dispatch({
type: "CHECK_USER",
payload: response,
});
};
};
The Problem
you are mixing two different implementations in checkUser to handle a promise which is clearly incorrect and leads to the issues.
The Solution
since your other parts of codes use the async/await so try to remove then/catch block from the response constant:
const checkUser = () => {
return async (dispatch) => {
const url = '/me';
try {
const token = await SecureStore.getItemAsycn("userToken);
const response = await api.post(url, {token})
dispatch({type: "CHECK_USER", payload: response})
} catch (error) {
// to proper action on failure case
}
}
}
Note 1: always use async/await in try/catch block. more on MDN documentation.
Optional
since you are trying to call two async actions (once for getting token and once for calling '/me' API), I encourage you to use two different try/catch blocks to handle the failure case for each async action separately. for example:
const checkUser = () => {
return async (dispatch) => {
let token = null;
try {
token = await SecureStore.getItemAsync("userToken");
} catch (err) {
// proper action in case of failure on getting the token from storage
}
// you may need to ignore API calls without the token, so:
try {
if(token){
const url = '/me';
const response = await api.post(url, {token});
dispatch({type: "CHECK_USER", payload: response});
}
} catch (err) {
// take proper action with the error response according to your applicaiton
}
}
}
The error message:
WARN Possible Unhandled Promise Rejection (id: 1):
Error: INVALID_STATE_ERR
send#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:31745:26
initialiseWebsocket#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:100544:21
loadUserData$#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:100610:40
tryCatch#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:7739:23
invoke#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:7912:32
tryCatch#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:7739:23
invoke#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:7812:30
http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:7822:21
tryCallOne#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:28596:16
http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:28697:27
_callTimer#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:29113:17
_callImmediatesPass#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:29152:17
callImmediates#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:29370:33
__callImmediates#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:3279:35
http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:3057:34
__guard#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:3262:15
flushedQueue#http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.dcgymappfrontend&modulesOnly=false&runModule=true:3056:21
flushedQueue#[native code]
invokeCallbackAndReturnFlushedQueue#[native code]
The useEffect that is being accused of being a problem:
React.useEffect(() => {
// Fetch the token from storage then navigate to our appropriate place
const loadUserData = async () => {
let userData;
try {
userData = await retrieveUserData();
} catch (e) {}
if(userData){
dispatch({ type: 'RESTORE_USER_DATA', userData: userData });
getChatData(userData, setChats, dispatch);
if(userData && !websocketInitialised){
console.log('web init called from *load user data*')
setWebsocketInitialised(true)
initialiseWebsocket(userData);
}
}
else{
dispatch({ type: 'RESTORE_USER_DATA_FAILED'});
}
};
loadUserData();
}, []);
The initialliseWebsocket function
function initialiseWebsocket(userData){
console.log('sending websocket initialisation data.');
websocket.send(JSON.stringify({
'action': 'init',
'data' : {'token': userData.token}
}));
}
the useState that is used above
const [websocketInitialised, setWebsocketInitialised] = React.useState(false);
async function getChatData(userData, setChats, dispatch){
console.log("fetching chat data");
// if we fail to download chat data, pull the old one from FS
const loadOldChatData = async () => {
let chats;
try {
chats = await retrieveChats();
} catch (e) {}
if(chats){
setChats(chats);
console.log("loaded cached chat data") ;
}
else{
setChats([]);
}
};
const onSuccess = (response) => {
if(response['chats']){
storeChats(response['chats']);
setChats(response['chats']);
console.log("chat data synced");
}
else{
loadOldChatData();
}
};
const onFailure = (response) => {
loadOldChatData();
};
fetch(Settings.siteUrl + '/messenger/get_chats/', {
method: "GET",
headers: {
"Content-type": "application/json; charset=UTF-8",
"Authorization": "Token " + userData.token
},
})
.then(response => response.json())
.then(response => {onSuccess(response)})
.catch(response => {onFailure(response)})
}
retrieveUseData() is most likely not the problem as this only started occuring after I added the other code.
Am I not supposed to use states like this or am I supposed to use the async key worked on functions? I tried that but I still have the same issue. You can see on the 4 line of the errors it mentions the 'initialiseWebsocket' function. I am guessing that is the route cause. I assume the solution will be some async version of it...
This error tell us that you didn't or forget to handle error from async code.
I refectory your code a bit, Tell me if you got any error message from console.log(error);
React.useEffect(() => {
// Fetch the token from storage then navigate to our appropriate place
(async () => {
try {
let userData = await retrieveUserData();
dispatch({ type: 'RESTORE_USER_DATA', userData });
await getChatData(userData, setChats, dispatch);
if (websocketInitialised) return;
console.log('web init called from *load user data*')
setWebsocketInitialised(true)
initialiseWebsocket(userData);
} catch (error) {
console.log(error);
dispatch({ type: 'RESTORE_USER_DATA_FAILED' });
}
})();
}, []);
And you should rename getChatData to setChatData, I also simplify those code also...
async function getChatData(userData, setChats, _dispatch) {
try {
let response = await fetch(Settings.siteUrl + '/messenger/get_chats/', {
method: "GET",
headers: {
"Content-type": "application/json; charset=UTF-8",
"Authorization": "Token " + userData.token
},
}),
data = await response.json(),
chats = data['chats'];
if (!chats?.length) throw "empty chat data, pull the old one from FS";
storeChats(chats);
setChats(chats);
} catch (_) {
// if we fail to download chat data, pull the old one from FS
await retrieveChats()
.then(chats => setChats(chats))
.catch(() => setChats([]))
}
}
"I don't really understand what you are doing with the async stuff."
async/await is just syntax sugar of promise, It allow you to work with async operation in a synchronous manner, some rules of async/await
In other to use await keyword, you need an async function.
you can make any function asynchronous, just by adding async keyword
async function always return promise
Lets see an example:
let delay = (ms, msg, bool) => new Promise((res, rej) => setTimeout(!bool ? res : rej , ms,msg));
This helper function create a promise for our example, it take 3 arguments, it take millisecond as 1st arg, to delay, 2rd is the message as payload. 3nd is Boolean; it true, then it will reject.
let delay = (ms, msg, bool) => new Promise((res, rej) => setTimeout(!bool ? res : rej, ms, msg));
let log = console.log;
async function myAsyncFn() {
let hello = await delay(100, "hello,");
let world = await delay(300, " world!");
// we use a symbol '#' to indicate that, its from `myAsyncFn`
log("#" , hello + world, "printed from async operation");
}
myAsyncFn();
log("As you can see that, this message print first");
// we are creating an async function and called immediately, In other to use `await keyword`
(async () => {
try {
let resolved = await delay(300,"resolved");
console.log(">" , `it ${resolved}!`);
// this will reject and catch via `try/catch` block;
let _ = await delay(600, "Error", true);
log("It will not print!");
// ...
} catch (error) {
log(">" , `we can catch "${error}" with try/catch, as like any sync code!`);
}
})()
As you can see that with async/await its look like everything is synchronous right? even everything execute asynchronously!
You just need to use await keyword to make every async operation synchronous.