Polling API every x seconds with react

Question

I have to monitoring some data update info on the screen each one or two seconds. The way I figured that was using this implementation:

    componentDidMount() {
        this.timer = setInterval(()=> this.getItems(), 1000);
      }
    
      componentWillUnmount() {
        this.timer = null;
      }
    
      getItems() {
        fetch(this.getEndpoint('api url endpoint'))
            .then(result => result.json())
            .then(result => this.setState({ items: result }));
      }

Is this the correct approach?

Answer 1

Well, since you have only an API and don't have control over it in order to change it to use sockets, the only way you have is to poll.

As per your polling is concerned, you're doing the decent approach. But there is one catch in your code above.

componentDidMount() {
  this.timer = setInterval(()=> this.getItems(), 1000);
}

componentWillUnmount() {
  this.timer = null; // here...
}

getItems() {
  fetch(this.getEndpoint('api url endpoint'))
    .then(result => result.json())
    .then(result => this.setState({ items: result }));
}

The issue here is that once your component unmounts, though the reference to interval that you stored in this.timer is set to null, it is not stopped yet. The interval will keep invoking the handler even after your component has been unmounted and will try to setState in a component which no longer exists.

To handle it properly use clearInterval(this.timer) first and then set this.timer = null.

Also, the fetch call is asynchronous, which might cause the same issue. Make it cancelable and cancel if any fetch is incomplete.

I hope this helps.

Answer 2

Although an old question it was the top result when I searched for React Polling and didn't have an answer that worked with Hooks.

// utils.js

import React, { useState, useEffect, useRef } from 'react';

export const useInterval = (callback, delay) => {

  const savedCallback = useRef();

  useEffect(() => {
    savedCallback.current = callback;
  }, [callback]);


  useEffect(() => {
    function tick() {
      savedCallback.current();
    }
    if (delay !== null) {
      const id = setInterval(tick, delay);
      return () => clearInterval(id);
    }
  }, [delay]);
}

Source: https://overreacted.io/making-setinterval-declarative-with-react-hooks/

You can then just import and use.

// MyPage.js

import useInterval from '../utils';

const MyPage = () => {

  useInterval(() => {
    // put your interval code here.
  }, 1000 * 10);

  return <div>my page content</div>;
}

Answer 3

You could use a combination of setTimeout and clearTimeout.

setInterval would fire the API call every 'x' seconds irrespective whether the previous call succeeded or failed. This can eat into your browser memory and degrade performance over time. Moreover, if the server is down, setInterval would continue to bombard the server not knowing its down status.

Whereas,

You could do a recursion using setTimeout. Fire a subsequent API call, only if the previous API call succeed. If previous call has failed, clear the timeout and do not fire any further calls. if required, alert the user on failure. Let the user refresh the page to restart this process.

Here is an example code:

let apiTimeout = setTimeout(fetchAPIData, 1000);

function fetchAPIData(){
    fetch('API_END_POINT')
    .then(res => {
            if(res.statusCode == 200){
                // Process the response and update the view.
                // Recreate a setTimeout API call which will be fired after 1 second.
                apiTimeout = setTimeout(fetchAPIData, 1000);
            }else{
                clearTimeout(apiTimeout);
                // Failure case. If required, alert the user.
            }
    })
    .fail(function(){
         clearTimeout(apiTimeout);
         // Failure case. If required, alert the user.
    });
}

Answer 4

@AmitJS94, there's a detailed section on how to stop an interval that adds onto the methods that GavKilbride mentioned in this article.

The author says to add a state for a delay variable, and to pass in "null" for that delay when you want to pause the interval:

const [delay, setDelay] = useState(1000);
const [isRunning, setIsRunning] = useState(true);
  useInterval(() => {
    setCount(count + 1);
  }, isRunning ? delay : null);

    useEffect(() => {
    function tick() {
      savedCallback.current();
    }

    if (delay !== null) {
      let id = setInterval(tick, delay);
      return () => clearInterval(id);
    }
  }, [delay]);

Definitely read the article to get a better understanding of the details -- it's super thorough and well-written!

Answer 5

As Vasanth mention, I preferred to:

• use setTimeout to measure the time between the end of the last request and the beginning of the next one
• make the first request straight away, not after the delay
• inspired by the answer from @KyleMit https://stackoverflow.com/a/64654157/343900

import { useEffect, useRef } from 'react';

export const useInterval = (
  callback: Function,
  fnCondition: Function,
  delay: number,
) => {
  const savedCallback = useRef<Function>();
  useEffect(() => {
    savedCallback.current = callback;
  }, [callback]);
  useEffect(() => {
    let id: NodeJS.Timeout;
    const tick = async () => {
      try {
        const response =
          typeof savedCallback.current === 'function' &&
          (await savedCallback.current());
        if (fnCondition(response)) {
          id = setTimeout(tick, delay);
        } else {
          clearTimeout(id);
        }
      } catch (e) {
        console.error(e);
      }
    };
    tick();
    return () => id && clearTimeout(id);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [delay]);
};

WORKS: Using fnCondition inside which can be a condition based on the response from the last request.

//axios-hooks
const {
    data,
    isLoadingData,
    getData,
} = api.useGetData();

const fnCondition = (result: any) => {
    const randomContidion = Math.random();
    //return true to continue
    return randomContidion < 0.9;
  };
useInterval(() => getData(), fnCondition, 1000);

DOES NOT WORK: Passing delay as null to stop useInterval like this does not work for me with this code: https://www.aaron-powell.com/posts/2019-09-23-recursive-settimeout-with-react-hooks/

(You might get the impression it works, but after a few starts/stops it breaks)

  const [isRunning, setIsRunning] = useState(true);
  const handleOnclick = () => {
    setIsRunning(!isRunning);
  };

  useInterval(() => getData(), isRunning ? 1000 : null);

  <button onClick={handleOnclick}>{isRunning ? 'Stop' : 'Start'}</button>

Sum up: I'm able to stop useInterval by passing fnCondition, but not by passing delay=null

Answer 6

Here's a simple, full solution, that:

• Polls every X seconds

• Has the option of increasing the timeout each time the logic runs so you don't overload the server

• Clears the timeouts when the end user exits the component

   //mount data
   componentDidMount() {
       //run this function to get your data for the first time
       this.getYourData();
       //use the setTimeout to poll continuously, but each time increase the timer
       this.timer = setTimeout(this.timeoutIncreaser, this.timeoutCounter);
   }
  
   //unmounting process
   componentWillUnmount() {
       this.timer = null; //clear variable
       this.timeoutIncreaser = null; //clear function that resets timer
   }
  
   //increase by timeout by certain amount each time this is ran, and call fetchData() to reload screen
   timeoutIncreaser = () => {
       this.timeoutCounter += 1000 * 2; //increase timeout by 2 seconds every time
       this.getYourData(); //this can be any function that you want ran every x seconds
       setTimeout(this.timeoutIncreaser, this.timeoutCounter);
   }