PHP MongoClient "No candidate servers found" with replica set - php

Question

Specs: PHP 5.3.10, Ubuntu 12.04 64 bit, Mongo driver 1.5.1, MongoDB 2.4.8
We have a single shard Mongo with two secondary replica sets. I can't seem to get PHP driver to utilize replica sets for high performance reads/writes. I'm getting "No candidate servers found" when trying to connect with the connection string provided below.
$connection = new MongoClient("mongodb://10.88.217.247:27017,10.88.217.247:27018",
array('username'=>"{$username}", 'password'=>"{$password}", 'replicaSet' => true));
This is what Mongo log sends:
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: start
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] send_packet: read from header: 36
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] send_packet: data_size: 259
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: can't find minWireVersion, defaulting to 0
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: can't find maxWireVersion, defaulting to 0
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: setting maxBsonObjectSize to 16777216
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: setting maxMessageSizeBytes to 48000000
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: can't find maxWriteBatchSize, defaulting to 1000
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: set name: rs-0, ismaster: 1, secondary: 0, is_arbiter: 0
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: the server name (mongo-0-0:27018) did not match with what we thought it'd be (10.88.218.248:27018).
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: the replicaset name is not set, so we're using rs-0.
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] found host: mongo-0-0:27018
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] found host: mongo-0-2:27018
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] found host: mongo-0-1:27018
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] ismaster: last ran at 1398292169
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] discover_topology: ismaster worked, but we need to remove the seed host's connection
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] mongo_connection_destroy: Destroying connection object for 10.88.218.248:27018;-;admin/scal/a6612d715d1a4f9549232ec4d599bf55;12199
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] mongo_connection_destroy: Closing socket for 10.88.218.248:27018;-;admin/scal/a6612d715d1a4f9549232ec4d599bf55;12199.
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] discover_topology: ismaster worked
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] discover_topology: found new host: mongo-0-0:27018
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.2.122] connection_create: creating new connection for mongo-0-0:27018
rs.status() JSON:
{
"set" : "rs-0",
"date" : ISODate("2014-04-24T15:13:39.000Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "mongo-0-0:27018",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 68415,
"optime" : Timestamp(1398285029, 1),
"optimeDate" : ISODate("2014-04-23T20:30:29.000Z"),
"self" : true
},
{
"_id" : 1,
"name" : "mongo-0-1:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 67984,
"optime" : Timestamp(1398285029, 1),
"optimeDate" : ISODate("2014-04-23T20:30:29.000Z"),
"lastHeartbeat" : ISODate("2014-04-24T15:13:38.000Z"),
"lastHeartbeatRecv" : ISODate("2014-04-24T15:13:38.000Z"),
"pingMs" : 0,
"syncingTo" : "mongo-0-0:27018"
},
{
"_id" : 3,
"name" : "mongo-0-2:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 63419,
"optime" : Timestamp(1398285029, 1),
"optimeDate" : ISODate("2014-04-23T20:30:29.000Z"),
"lastHeartbeat" : ISODate("2014-04-24T15:13:38.000Z"),
"lastHeartbeatRecv" : ISODate("2014-04-24T15:13:38.000Z"),
"pingMs" : 0,
"syncingTo" : "mongo-0-0:27018"
}
],
"ok" : 1
}

Answer 1

Several things you might want to notice when you setup a replica set:
when building the replica set, the first member will be named using the server's host name. So when you access the server, it will NOT access the host in the connection string. Instead, it gets available server list from there, and tries to connect to the host names in that list. I explained some details here. You can also find information in the mongodb c# driver tutorial :
It is required that each MongoDB server have a name that is DNS resolvable by the client machine. Each MongoDB server reports its hostname back through the isMaster command and the driver uses this name to talk with the server. This issue can occur when the seed list contains an IP address and the MongoDB server reports back a hostname that the client machine is unable to resolve.
When you access a replica set, you should provide a replia set name with parameter replicaSet=[set name], something the following.
mongodb://hostname1,hostname2/dbName?replicaSet=rs0
Don't mix up servers from different replica set because:
If you have multiple servers listed, and one is part of a replica set and another is not, then the connection mode is non-deterministic. Be sure that you are not mixing server types on the connection string.
Note the bind ip of your mongo server. If I remember it correctly, in some distributions it defaults to listening on 127.0.0.1:27017. Thus you'll never get connected from a guest machine. Try set the following line in /etc/mongodb.conf:
bind_ip = 0.0.0.0
Back to your question. from the log:
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.1.123] ismaster: the replicaset name is not set, so we're using rs-0.
It tells you to provide the replica set name. and it assumes it's rs-0 (is the name correct?)
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.1.123] found host: mongo-0-0:27018
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.1.123] found host: mongo-0-2:27018
[Wed Apr 23 22:29:29 2014] [error] [client 170.171.1.123] found host: mongo-0-1:27018
Says you have 3 members in your replica set. And the driver's going to connect to them by using their names, which would be:
mongo-0-0:27018
mongo-0-1:27018
mongo-0-2:27018
If you want them to work, add to your clients' /etc/hosts
[ip of mongo] mongo-0-0:27018
[ip of mongo] mongo-0-0:27018
[ip of mongo] mongo-0-0:27018
Or if you want to change these names, use the following lines:
var conf = rs.conf();
conf.members[0].host = "..." // your new name for member0
conf.member[1].host = "..."
conf.member[2].host = "..."
rs.reconfig(conf)