How to check if mongos connection still alive in Node.JS?

Question

Let's imagine we have Node.JS app which is connecting to the Mongos process. But suddenly Mongos failed. How our app could now about it?

var db = null;  
mongo.MongoClient.connect('mongodb://127.0.0.1:27017/test', function(err, mydb) {
    if(err) throw err;
    db = mydb
});

..... on response we have .....
db.collection('test_collection', function(err, collection){
    collection.find({}).toArray(function(err, documents){
        // doing some work here
        // but if Mongos failed, we are blocked on this stage
    }); 
});

score 0 · Answer 1 · answered Feb 26 '14 at 11:01

0

Would you not want to do the same thing that you're doing at connect, but within the function?

i.e.

...
collection.find({}).toArray(function(err, documents) {
   if(err) {
       throw err; //or do something equivalent.  It doesn't really matter if the connection has failed, as it will still throw an error.
   } else {
       ///continue processing
   }
  ....

Alternatively, if you use a 3rd party mongo manager, such as mongoose, you can do something like this globally:

mongoose.connect('mongodb://' + config.mongo.host + '/' + config.mongo.db);
var db = mongo.connection;
db.on('error', console.error.bind(console, 'connection error: '));

answered Feb 26 '14 at 11:01

Stephen Wright

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it's amazing, but i still havn't got an error in your code. I can't understand why. – user3355410 Feb 26 '14 at 11:05
Probably it's because i launch it on Windows? – user3355410 Feb 26 '14 at 11:19
Are you even dropping into the err? What happens if you console.log inside the `if(err)` rather than a `throw err;`? – Stephen Wright Feb 26 '14 at 12:58

How to check if mongos connection still alive in Node.JS?

1 Answers1