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I have a mongodb replica set with the following config:

  • M1 (192.168.77.3) primary (host App1)
  • M2 (192.168.77.4) secondary (host App2)
  • M3 (192.168.77.5) secondary (host App3)
  • M4 arbitrator

Here is my Express code to connect to db (I use mongoose as the ODM):

 const config = {
    db: `mongodb://192.168.77.3,192.168.77.4,192.168.77.5/mydb`,
    dbOptions: {
      useMongoClient: true,
      reconnectTries: Number.MAX_VALUE,
      replicaSet: process.env.REPLICA_SET,
      poolSize: 100,
      keepAlive: 1,
      connectTimeoutMS: 30000,
      socketTimeoutMS: 300000,
      w: 1
    }
  }
mongoose.connect(config.db, config.dbOptions, (error) => {
  if (error) {
    console.log('Error on connecting to th db: ', error)
    console.log('\x1b[31m', '*** PLEASE CONNECT TO DATABASE BEFORE RUN SERVER', '\x1b[0m')
    process.exit(1)
  }
  callback()
})

The app works as expected. When M1 get down, either M2 or M3 get elected to be the primary, the App2 and App3 still working, BUT the App1 CAN'T connect to the replica set with the error message: 

MongoError: failed to connect to server [localhost:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]

This is my mongodb config on App1:

storage:
  dbPath: /var/lib/mongodb
  journal:
    enabled: true

systemLog:
  destination: file
  logAppend: true
  path: /var/log/mongodb/mongod.log

net:
  port: 27017
  bindIp: [127.0.0.1, 192.168.77.3]

replication:
  oplogSizeMB: 3000
  replSetName: my_rs

Is there any wrong in my config?

Justin
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1 Answers1

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You CAN NOT mix IP-addresses of multiple nodes at one single config file.

Your bindIp string

bindIp: [127.0.0.1, 192.168.77.4, 192.168.77.5]

should be

bindIp: "127.0.0.1,192.168.77.3"

at first node and

bindIp: "127.0.0.1,192.168.77.4"

at second node. And so on... So, you can have localhost bind and other addresses what belong to that node.

My initial answer was wrong because I thought that it has something to do with mongooos, what I don't know.

JJussi
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  • Thanks for your advice, I'll try this approach! – Justin Nov 29 '17 at 03:58
  • Oh, I just realize that you probably have big configuration error here. Do you have three different data nodes with three different IP addresses or do you have one physical node with three mongod instances and you have tried to configure those to different IP addresses? If you have three distinct nodes (as it should be), your mongodb config line must have (at bindIp) only that IP-address (ONE) what that node have, not all ip-addresses. I will fix my answer... – JJussi Nov 29 '17 at 04:30
  • Yes, I have 3 mongodb nodes on 3 physical servers. They are on the same data center so I can use the private IP (192.168.77.3, .4 and .5). And, what is the different btw `[127.0.0.1, 192.168.77.4]` and `"127.0.0.1,192.168.77.4"` style? By the way, the new config is still not working :( – Justin Nov 29 '17 at 04:45
  • That [] format was accepted with older mongod versions. Current versions don't accept it and give strange error message what of course don't tell what is wrong actually. What comes to your problem. Locally, at mongod config file you tell node (with bindIp) what NIC addresses it should listen. At application end, you need to use full connection URL (all replica set node addresses, database, replica set name,...). And you can always give those node addresses in any order. – JJussi Nov 29 '17 at 09:46