How to retry a request and overwrite the reponse in a Collection Post Response script?

[maxiride]

👉 Skip to #5523 (comment) for an updated situation

---

I am interacting with a non-standard API, the POST /login endpoint requires a JSON with some credentials (persisted in a Collection environment variable) and returns a JWT token with an expiration.

I am trying to implement a retry mechanism for when the token expires, so that I don't have to manually update it. I've tried to implement a collection post request script but when the token expires I am still receiving a 401. Through the console I am not understanding if the request fails because:

• The method used bru.setEnvVar to store the token set a different token variable and not the collection's one defined in step 1 below, so the new request still uses the expired token
• The token is updated successfully but bru.setNextRequest(req.getName()) doesn't actually retry the request.

What I have done so far

1. Configured the Collection auth to use Bearer Token and set its value to a variable {{token}}

2. Configured the following post script

// if original request fails with 401, perform a token refresh and retry the original request
if (res.status === 401) {
    console.log('token expired, attempting refresh...')

    const loginRes = await bru.sendRequest({
        method: "POST",
        url: `${bru.getEnvVar('BASE_URL')}/login`,
        data: {
            credential: bru.getEnvVar('LOGIN_CREDENTIALS_BASE64')
        }
    });
    
    // login request succeded
    if (loginRes.status === 200) {
      bru.setVar('token', loginRes.data.token)
      console.log('token updated')
      
      bru.setNextRequest(req.getName())
    }      
}

I will gladly appreciate any possible guidance, because other than fixing this specific issue I feel like I can't troubleshoot the issue at all which is more important than the actual solution.

---

Edits:

• Found out that it is needed to use setVar and getVar for runtime variables.
• Tried to manipulated the original request with no success. req.setHeader() has no effect.

if (loginRes.status === 200) {
/.../
      console.debug('original req', req)
      
      req.setHeader('Authorization', `Bearer ${bru.getVar('token')}`)

      console.debug('updated req', req)
      
      const retryRes = await bru.sendRequest(req)
      
      console.log('retryRes', retryRes)

/.../

[maxiride]

After a lot fiddling I managed to update the original request headers and execute again the original request with the updated auth header. The new request is executed correctly and the state of retryRes is as expected.

However, I just found out that the res object is read only so I can't manipulate the original response and overwrite if with the new one 😶

Collection Post response script

// if original request fails with 401, perform a token refresh and retry the original request
if (res.status === 401) {
    console.log('token expired, refresh...')

    const loginRes = await bru.sendRequest({
        method: "POST",
        url: `${bru.getEnvVar('BASE_URL')}/login`,
        data: {
            credential: bru.getEnvVar('LOGIN_CREDENTIALS_BASE64')
        }
    });
    
    if (loginRes.status === 200) {
      bru.setVar('token', loginRes.data.token)
      console.log('token updated')

      req.headers = {
        ...req.headers, // re-apply original headers
        'Authorization': `Bearer ${bru.getVar('token')}`, // any field defined after then expansion ...req.headers overwrites previously defined fields
      }
      
      const retryRes = await bru.sendRequest(req)
      
      console.log('retryRes', retryRes)

      res = retryRes // res read-only 
    }      
}

[maxiride]

Eventually I understood the whole approach was wrong. The token status is best checked before making a request.

Here is a working collection pre-request script.

const moment = require('moment');

const exp =  bru.getVar('token_expiration_ts')

if (!exp || moment().isAfter(exp)) {
  console.debug('token expired or missing, refreshing...')

  const loginRes = await bru.sendRequest({
      method: "POST",
      url: `${bru.getEnvVar('BASE_URL')}/login`,
      data: {
          credential: bru.getEnvVar('LOGIN_CREDENTIALS_BASE64')
      }
  });
  
  bru.setVar('token', loginRes.data.token)
  bru.setVar('token_expiration_ts', moment().add(loginRes.data.expires_in, 'seconds').format() )
}