Nodejs connect mongo

Question

I try to move datastorage in my node app to mongo db. But I have a simple problem with mongo db.

I have a button, clicked in website, will call /datastore

app.post('/datastore', (req, res) => {

    client.connect(err => {
        var dbo = client.db("test");
        dbo.listCollections().toArray(function(err, items){
            if (err) throw err;

            console.log(items);
            if (items.length == 0)
                console.log("No collections in database")
        });

        client.close();
    });

});

It works fine for the first time I click the button. But if I click the second time the button I get errors messages:

the options [servers] is not supported the options [caseTranslate] is not supported the options [dbName] is not supported the options [credentials] is not supported /Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/utils.js:132 throw err; ^

MongoError: Topology was destroyed at initializeCursor (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb-core/lib/cursor.js:596:25) at nextFunction (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb-core/lib/cursor.js:456:12) at CommandCursor.Cursor.next (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb-core/lib/cursor.js:766:3) at CommandCursor.Cursor._next (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/cursor.js:216:36) at fetchDocs (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/operations/cursor_ops.js:217:12) at toArray (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/operations/cursor_ops.js:247:3) at executeOperation (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/utils.js:416:24) at CommandCursor.Cursor.toArray (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/cursor.js:829:10) at client.connect.err (/Users/ingofoerster/Downloads/development/testrunner/start.js:256:35) at result (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/utils.js:410:17) at executeCallback (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/utils.js:402:9) at err (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/operations/mongo_client_ops.js:286:5) at connectCallback (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/operations/mongo_client_ops.js:265:5) at topology.connect (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/operations/mongo_client_ops.js:417:5) at ReplSet.connectHandler (/Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb/lib/topologies/replset.js:343:9) at Object.onceWrapper (events.js:281:20) at ReplSet.emit (events.js:193:13) at /Users/ingofoerster/Downloads/development/testrunner/node_modules/mongodb-core/lib/topologies/replset.js:786:18 at processTicksAndRejections (internal/process/task_queues.js:79:9)

I cannot explain why this happens, because I have the client.close() in my code. Any idea why I can not call the function more than one time?

Amolpskamble Amolpskamble · Accepted Answer · 2019-07-18T08:54:18

When you clicked the button for the first time, you are able to get the result as expected, but after getting the result you are also closing the connection by calling client.close(); , which is not letting MongoDB reconnect for the second time.

Ideally, you should reuse the existing connection instead of calling connect method for each API call.

Connection pooling example is taken from here

var express = require('express');
var mongodb = require('mongodb');
var app = express();

var MongoClient = require('mongodb').MongoClient;
var db;

// Initialize connection once
MongoClient.connect("mongodb://localhost:27017/integration_test", function(err, database) {
  if(err) throw err;

  db = database;

  // Start the application after the database connection is ready
  app.listen(3000);
  console.log("Listening on port 3000");
});

// Reuse database object in request handlers
app.get("/", function(req, res) {
  db.collection("replicaset_mongo_client_collection").find({}, function(err, docs) {
    docs.each(function(err, doc) {
      if(doc) {
        console.log(doc);
      }
      else {
        res.end();
      }
    });
  });
});

Nodejs connect mongo

1 Answers