nodejs mongodb driver drops connection when idle

Question

nodejs mongodb driver drops connection when idle and does not reconnect.

Background

The script below connects to mongodb and stores a reference to the database in a global variable "db"

config = require("./config.js");
express = require("express");
mongodb = require("mongodb"); 

db = null;

options = {
  auto_reconnect: true,
  db: {
    w: 1
  }
};

mongodb.MongoClient.connect(config.mongo, options, function(err, database) {

  if (err !== null)
    return console.log(err);

  db = database;
  console.log("successfully connected to mongodb");

  db.on("close", (function() {
    return console.log("Connection to database closed automagically " + arguments);
  }));

  db.on("error", function(err) {
    return console.log("Db error " + err);
  });

  app.listen(port);

  return console.log("listening for connections on " + port);

});

Whenever i receive an insert request from client the following function is invoked:

insert = function(collectionName, object) {
  return db.collection(collectionName).insert(object, {w: 1}, (function(err) {
    return console.log("insert complete with err = " + err);
  }));
};

Issue

When the server receives an insert request after a long time it fails silently or sometimes throws an error stating unable to insert object (Error: failed to connect to [host:port])

Question

Is there a way to prevent this behaviour? I have tried to use auto_reconnect option and write concern of 1 but none of these have helped.

Thanks!

Answer 1

Solved!

1. Set server.socketoptions.keepAlive to 1. Simply update the options object like so:

   options = {
     auto_reconnect: true,
     db: {
       w: 1
     },
     server: {
       socketOptions: {
         keepAlive: 1
       }
     }
   };
   

2. Ping the database at regular intervals. Here's a code snippet that does exactly that:

   printEventCount = function() {
     db.collection("IOSEvents").count(function(err, numberOfEvents) {
       console.log(new Date() + ": error = " + err + ", number of events = " + numberOfEvents);
       ping();
     });
   };
   
   ping = function() {
     if (config.pingPeriod === 0)
       return;    
     setTimeout(printEventCount, config.pingPeriod);
   };