Mongodb - replica set - max connections - node.js

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;