Mongodb - replica set - max connections

Question

I have a replicaset of 3 mongo node, 1 primary, 1 secondary and 1 arbiter.

Connected on this replicaset, i have 20 node process, on 20 different serveur using their own connections to the replicaset. All those process use mongoose.

My primary replicaset show the following :

rsProd:PRIMARY> db.serverStatus().connections
{ "current" : 284, "available" : 50916, "totalCreated" : NumberLong(42655) }

From time to time, when i restart some nodejs node i have the following errors :

mongodb no valid seed servers in list

My connection string to the replicaset is the following :

"mongodb://mongo2aws.abcdef:27017/dbname,mongo1.abcdef:27017/dbname"

And my db options are the following :

       config.db_options = {
            user:           "MYUSER",
            pass:           "MYPASSWORD",
            replset: {
                rs_name:    "RSNAME",
                ssl:        true,
                sslValidate:false,
                sslCA:      ca,
                ca:         ca,
                sslKey:     key,
                sslCert:    key
            },
            socketOptions : {
                keepAlive :         1,
                connectTimeoutMS :  1000
            },
            server: {
                ssl:        true,
                sslValidate:false,
                sslCA:      ca,
                ca:         ca,
                sslKey:     key,
                sslCert:    key
            },
            auth: {
                authdb: 'MYAUTHDB'
            }
        };

I haven't this error when i was running only 16 node process. According to this i suppose that i have reach a limit of max concurrent connections or something like this.

But, if i restart again crashing node, it finally seems to work.

Why mongo / mongoose raise this error ? What can i do to prevent this / increase limit ?

Thanks in advance Best regards.

Answer 1

Solved by increasing ulimit open files

Default ulimit for open files in AWS EC2 ubuntu server is set to 1000 by default.

In addition, adding reconnect options prevent this problem :

config.db_options.reconnectTries=10;
config.db_options.reconnectInterval=500;
config.db_options.poolSize=20;
config.db_options.connectTimeoutMS=5000;