Nodejs - response body status from OData $batch

Question

In NodeJS and express I am handling a batch request to a OData API. Sometimes the OData service returns invalid results in the response which is denoted by a status 500 (could be more than one, since this is a OData batch response), even though the request header status code returns 200 because the connection to the API itself was successful.

I am new to NodeJS and am not sure how / the best way to detect these status 500 in the response body so that I can retry the request (reason is these 500 errors are usually timeouts and on the next retry goes away).

Do I need a package to be able to retrieve or intercept res.body? I don't see it available in express.

Request and response example

Request header

Request URL: https://odata/$batch
Request Method: POST
Status Code: 202 Accepted
Remote Address: xxxx
Referrer Policy: no-referrer-when-downgrade

Response

--batch_1564714041997_0
Content-Type: application/http
Content-Transfer-Encoding: binary

HTTP/1.1 500 OK
Content-Type: text/plain;charset=utf-8

Internal server error

--batch_1564714041997_0
Content-Type: application/http
Content-Transfer-Encoding: binary

HTTP/1.1 500 OK
Content-Type: text/plain;charset=utf-8

Internal server error


--batch_1564714041997_0--

Answer 1

I would use a regular expression and a capturing group for the HTTP status code.

var regExForHTTPStatusCodeDetection = RegExp('HTTP\/1\.\\d (\\d{3})','g');

var requestNumber = 1;

while ((regExMatches = regExForHTTPStatusCodeDetection.exec(res.body)) !== null) {

  // Get status code from first capturing group
  var httpStatusCode = regExMatches[1];

  // Output for above example:
  // "Request 1 has returned HTTP 500."
  // "Request 2 has returned HTTP 500."
  console.log(`Request ${requestNumber} has returned HTTP ${}.`);
  requestNumber++;
}