Need a way to set res object after couchbase DB call “Error: Can't set headers after they are sent”

Question

var express = require('express');

var search = express.Router();

search.get('/', function(req, res, next) {
    console.log('1');

    dbCall(function(error, result) {
        if (error) {
            res.status(404).json();
        } else {
            res.json(result);
        }
    });

    console.log('last');
    next();
});

var dbCall = function(callback) {
    var couchbase = require('couchbase');
    var cluster = new couchbase.Cluster('couchbase://127.0.0.1');
    var bucket = cluster.openBucket('default');

    var doc;

    var ViewQuery = couchbase.ViewQuery;

    var query = ViewQuery.from('dev_test', 'allData');

    bucket.query(query, function(err, viewResults) {
        if (err) {
            callback(err, null);
        } else {
            console.log('inqueryCall');
            var results = viewResults;
            callback(null, results);
            console.log(results);
        }
    });
};

module.exports = search;

Here's the error that I get is : Error: Can't set headers after they are sent. at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:346:11)

Can someone please explain the issue here(not just the solution)?

I've added console.log and the issue here is that the couchbase call to async

Answer 1

Remove next() call, that is causing this error. next() is used in middleware to pass the flow to next middleware or endpoint/route

search.get('/', function(req, res, next) {

   dbCall(function(error, result) {
       if (error) {
           res.status(404).json();
       } else {
           res.json(result);
       }
   });
});