Node JS: Request Loop Until Status Code 200

Question

I currently have working code that does a request and checks if it receives a successful status code of 200. I would like to grow on this and loop it where it will keep sending requests until the status code is 200. I tried using a while loop but was not receiving the correct results. Thanks for the help!

request('http://0.0.0.0:9200', function (error, response, body) {
    if (!error && response.statusCode == 200) {
      console.log('success');
      do(something);
    }
    else {
      console.log('fail');
    }
});

Could wrap the request in a function, then have it call itself on the fail condition? — millerbr
– millerbr, Commented Feb 3, 2016 at 19:22

crackmigg · Accepted Answer · 2016-02-03 20:08:58Z

13

Would be something like:

let retry = (function() {
  let count = 0;

  return function(max, timeout, next) {
    request('http://0.0.0.0:9200', function (error, response, body) {
      if (error || response.statusCode !== 200) {
        console.log('fail');

        if (count++ < max) {
          return setTimeout(function() {
            retry(max, timeout, next);
          }, timeout);
        } else {
          return next(new Error('max retries reached'));
        }
      }

      console.log('success');
      next(null, body);
    });
  }
})();

retry(20, 1000, function(err, body) {
    do(something);
});

You can set a max number of retries and a timeout between retries. So that you do not introduce an infinite loop, and you do not deliver the final punch to an overloaded request target ^^

edited Feb 3, 2016 at 20:08

answered Feb 3, 2016 at 20:03

crackmigg

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4 Comments

emarel Over a year ago

would you mind explaining how this functionality works. I have implemented it but understanding is still a bit fuzzy.

crackmigg Over a year ago

What exactly do you not understand?

scavenger Over a year ago

this works but request is deprecated, can you post an update with axios pretty please?

crackmigg Over a year ago

@scavenger its not 2016 anymore and we have observables that have retry operator, you can check retry ref official doc even takes this as their example. Also if you are using axios you should probably check out axios-retry.

Eyal Cohen · Accepted Answer · 2018-01-01 09:40:25Z

I wanted a little more intuitive answer including promises. I build on top of miggs answer within a try/catch the code below with promises and axios.

Based on a simple example of recursive functions

const throwNumbers = (count = 0) => {
  console.log(count);
  if (count++ < 10) {
    throwNumbers(count);
  } else {
    console.log('max reached');
  };
};

You can put anything else on the try part and handle error codes in the catch part. You have to set a max number of retries, which is 10 in my case.

let getResponse = async(count = 0) => {
  try {
    const axiosResponse = await axios.get(someURL, {
      params: {
        parameter1: parameter1,
      },
    });
    return axiosResponse;
  } catch (error) {
    if (error || error.status != 200) {
      console.error('failed, retry');

      if (count++ < 10) {
        return getResponse(count);
      } else {
        throw new Error('max retries reached');
      };
    } else {
      throw error;
    };
  };
};

You would call the function with the following and handle the body or whatever with the response value.

let response = await getResponse();
console.log('This is the response:', response);

Has no timeout but works for me.

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