Table of Contents
Overview
So far we configured and spoke about two possible configurations with Mongo:
- Replication
- Sharding
Let's discuss overview of each at a time:
Replication
This configuration is known also as Active / Passive
Pros:
- Provides redundancy in case you loose your site
- Can be used as backup site and thus not loading the primary
- Can be used for select only queries
Cons:
- Requires additional Server on other location
- Requires further configuration in case of a failover
- Secondary servers cannot be used for read/write operations
Sharding
This configuration is known as Active / Active
Pros:
- Provides load balanced configuration
- Increases the performance
- Can be used to store regional data, thus each region accesses it's data way faster
Cons:
- Requires additional server on the same location
- In case of even one server shuts down, its collections aren't available.
- Backups should be taken separately for each shard server.
Replicated Shards
So, what if we can combine both architectures, as so:
As so, we can combine the PROs of both configuration and eliminates almost all CONs.
Configuration
Configuration isn't done so differently than the previous implementations, we have to just combine both ways as follows:
Configuration Database
The setup for the configuration database is like any other Mongo database and it is started as follows:
[root@lparamongo mongo]# mongod -f /etc/mongod.conf -fork --configsvr about to fork child process, waiting until server is ready for connections. forked process: 1336 child process started successfully, parent exiting [root@lparamongo mongo]#
With this, we started a mongo database on port 9005 with db path /app/mongo and as a CONFIGSVR! You can also replicate that database for more redundancy if you wish.
Shard Controller
Shard controller is used for the Shard server re-configuration (Addition or Removal of a node for example) or as a proxy (front point) for the clients to connect and be load-balanced among the shards.
[root@lparbmongo ~]# mongos --configdb lparamongo:9005 --port 9005 --chunkSize 1
2018-06-07T15:02:37.778+0200 warning: running with 1 config server should be done only for testing purposes and is not recommended for production
2018-06-07T15:02:37.781+0200 [mongosMain] MongoS version 2.6.12 starting: pid=1283 port=9005 64-bit host=lparbmongo (--help for usage)
2018-06-07T15:02:37.781+0200 [mongosMain] db version v2.6.12
2018-06-07T15:02:37.781+0200 [mongosMain] git version: d73c92b1c85703828b55c2916a5dd4ad46535f6a
2018-06-07T15:02:37.781+0200 [mongosMain] build info: Linux build5.ny.cbi.10gen.cc 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49
2018-06-07T15:02:37.781+0200 [mongosMain] allocator: tcmalloc
2018-06-07T15:02:37.781+0200 [mongosMain] options: { net: { port: 9005 }, sharding: { chunkSize: 1, configDB: "lparamongo:9005" } }
2018-06-07T15:02:37.829+0200 [mongosMain] creating WriteBackListener for: lparamongo:9005 serverID: 000000000000000000000000
018-04-06T20:11:11.070+0200 [Balancer] warning: could not initialize balancer, please check that all shards and config servers are up: socket exception [CONNECT_ERROR] for lparcmongo:9005
2018-04-06T20:11:11.070+0200 [Balancer] will retry to initialize balancer in one minute
^C2018-04-06T20:11:23.910+0200 [signalProcessingThread] got signal 2 (Interrupt), will terminate after current cmd ends
2018-04-06T20:11:58.751+0200 [mongosMain] writing initial config version at v5
2018-04-06T20:11:58.760+0200 [mongosMain] about to log new metadata event: { _id: "lparbmongo-2018-04-06T18:11:58-5ac7b86e1bf26be6f336303e", server: "lparbmongo", clientAddr: "N/A", time: new Date(1523038318760), what: "finished upgrade of config database", ns: "config.version", details: { from: 0, to: 5 } }
2018-04-06T20:11:58.790+0200 [mongosMain] upgrade of config server to v5 successful
2018-04-06T20:11:58.790+0200 [mongosMain] distributed lock 'configUpgrade/lparbmongo:9005:1523038318:1804289383' unlocked.
2018-04-06T20:11:59.023+0200 [mongosMain] scoped connection to lparamongo:9005 not being returned to the pool
2018-04-06T20:11:59.023+0200 [Balancer] about to contact config servers and shards
2018-04-06T20:11:59.024+0200 [mongosMain] waiting for connections on port 9005
2018-04-06T20:11:59.024+0200 [Balancer] config servers and shards contacted successfully
2018-04-06T20:11:59.024+0200 [Balancer] balancer id: lparbmongo:9005 started at Apr 6 20:11:59
2018-04-06T20:11:59.053+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1523038318:1804289383' acquired,
Replica Set A
Each Replica Set should be started, initialized and configured as follows:
Starting Node 1
[root@lparcmongo app]# mongod --dbpath /app/mongo2 --logpath /app/mongo2/logmong.log --port 9006 --fork --replSet repSetA about to fork child process, waiting until server is ready for connections. forked process: 1553 child process started successfully, parent exiting
Starting Node 2
[root@lparcmongo mongo]# mongod --dbpath /app/mongo --logpath /app/mongo/logmong.log --port 9005 --fork --replSet repSetA about to fork child process, waiting until server is ready for connections. forked process: 1899 child process started successfully, parent exiting
Once both Nodes has been started, we can initiate the replica set configuration:
[root@lparcmongo mongo]# mongo --port 9005
MongoDB shell version: 2.6.12
connecting to: 127.0.0.1:9005/test
> use admin
switched to db admin
> rs.initiate()
{
"info2" : "no configuration explicitly specified -- making one",
"me" : "lparcmongo:9005",
"info" : "Config now saved locally. Should come online in about a minute.",
"ok" : 1
}
> rs.status()
{
"set" : "repSetA",
"date" : ISODate("2018-04-06T18:07:13Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "lparcmongo:9005",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 42,
"optime" : Timestamp(1523038024, 1),
"optimeDate" : ISODate("2018-04-06T18:07:04Z"),
"electionTime" : Timestamp(1523038024, 2),
"electionDate" : ISODate("2018-04-06T18:07:04Z"),
"self" : true
}
],
"ok" : 1
}
Once we are done we can add the 2nd node to the First Replica set:
repSetA:PRIMARY> rs.add("lparcmongo:9006")
{ "ok" : 1 }
repSetA:PRIMARY> rs.status()
{
"set" : "repSetA",
"date" : ISODate("2018-04-06T18:07:45Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "lparcmongo:9005",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 74,
"optime" : Timestamp(1523038061, 1),
"optimeDate" : ISODate("2018-04-06T18:07:41Z"),
"electionTime" : Timestamp(1523038024, 2),
"electionDate" : ISODate("2018-04-06T18:07:04Z"),
"self" : true
},
{
"_id" : 1,
"name" : "lparcmongo:9006",
"health" : 1,
"state" : 5,
"stateStr" : "STARTUP2",
"uptime" : 4,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2018-04-06T18:07:43Z"),
"lastHeartbeatRecv" : ISODate("2018-04-06T18:07:44Z"),
"pingMs" : 0,
"lastHeartbeatMessage" : "initial sync need a member to be primary or secondary to do our initial sync"
}
],
"ok" : 1
Once the 2nd Server has been added we should see the following output from the rs.status() command:
repSetA:PRIMARY> rs.status()
{
"set" : "repSetA",
"date" : ISODate("2018-04-06T18:08:00Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "lparcmongo:9005",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY", <- Primary / Active
"uptime" : 89,
"optime" : Timestamp(1523038061, 1),
"optimeDate" : ISODate("2018-04-06T18:07:41Z"),
"electionTime" : Timestamp(1523038024, 2),
"electionDate" : ISODate("2018-04-06T18:07:04Z"),
"self" : true
},
{
"_id" : 1,
"name" : "lparcmongo:9006",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY", <- Secondary / Passive
"uptime" : 19,
"optime" : Timestamp(1523038061, 1),
"optimeDate" : ISODate("2018-04-06T18:07:41Z"),
"lastHeartbeat" : ISODate("2018-04-06T18:07:59Z"),
"lastHeartbeatRecv" : ISODate("2018-04-06T18:08:00Z"),
"pingMs" : 0,
"syncingTo" : "lparcmongo:9005"
}
],
"ok" : 1
}
Replica Set B
The replica B is configured the same way as replica A:
[root@lpardmongo mongo]# mongod --dbpath /app/mongo --logpath /app/mongo/logmong.log --port 9005 --fork --replSet repSetB
about to fork child process, waiting until server is ready for connections.
forked process: 1290
child process started successfully, parent exiting
[root@lpardmongo mongo2]# mongod --dbpath /app/mongo2 --logpath /app/mongo2/logmong.log --port 9006 --fork --replSet repSetB
about to fork child process, waiting until server is ready for connections.
forked process: 1341
child process started successfully, parent exiting
[root@lpardmongo mongo2]# mongo --port 9005
MongoDB shell version: 2.6.12
connecting to: 127.0.0.1:9005/test
> use admin
switched to db admin
> rs.initiate()
{
"info2" : "no configuration explicitly specified -- making one",
"me" : "lpardmongo:9005",
"info" : "Config now saved locally. Should come online in about a minute.",
"ok" : 1
}
> rs.status()
{
"set" : "repSetB",
"date" : ISODate("2018-04-06T18:10:37Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "lpardmongo:9005",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 117,
"optime" : Timestamp(1523038227, 1),
"optimeDate" : ISODate("2018-04-06T18:10:27Z"),
"electionTime" : Timestamp(1523038227, 2),
"electionDate" : ISODate("2018-04-06T18:10:27Z"),
"self" : true
}
],
"ok" : 1
}
repSetB:PRIMARY> rs.add("lpardmongo:9006
2018-04-06T20:10:47.691+0200 SyntaxError: Unexpected token ILLEGAL
repSetB:PRIMARY> rs.add("lpardmongo:9006")
{ "ok" : 1 }
repSetB:PRIMARY> rs.status()
{
"set" : "repSetB",
"date" : ISODate("2018-04-06T18:10:55Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "lpardmongo:9005",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 135,
"optime" : Timestamp(1523038253, 1),
"optimeDate" : ISODate("2018-04-06T18:10:53Z"),
"electionTime" : Timestamp(1523038227, 2),
"electionDate" : ISODate("2018-04-06T18:10:27Z"),
"self" : true
},
{
"_id" : 1,
"name" : "lpardmongo:9006",
"health" : 1,
"state" : 5,
"stateStr" : "STARTUP2",
"uptime" : 2,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2018-04-06T18:10:55Z"),
"lastHeartbeatRecv" : ISODate("2018-04-06T18:10:55Z"),
"pingMs" : 0,
"lastHeartbeatMessage" : "initial sync need a member to be primary or secondary to do our initial sync"
}
],
"ok" : 1
}
repSetB:PRIMARY> rs.status()
{
"set" : "repSetB",
"date" : ISODate("2018-04-06T18:10:57Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "lpardmongo:9005",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 137,
"optime" : Timestamp(1523038253, 1),
"optimeDate" : ISODate("2018-04-06T18:10:53Z"),
"electionTime" : Timestamp(1523038227, 2),
"electionDate" : ISODate("2018-04-06T18:10:27Z"),
"self" : true
},
{
"_id" : 1,
"name" : "lpardmongo:9006",
"health" : 1,
"state" : 5,
"stateStr" : "STARTUP2",
"uptime" : 4,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2018-04-06T18:10:57Z"),
"lastHeartbeatRecv" : ISODate("2018-04-06T18:10:57Z"),
"pingMs" : 0,
"lastHeartbeatMessage" : "initial sync need a member to be primary or secondary to do our initial sync"
}
],
"ok" : 1
}
repSetB:PRIMARY>
Configure the Replicated Shards
So in order to add the replicaSets instead of the servers themselves, we have to add them in a special way:
[root@lparbmongo ~]# mongo --port 9005
MongoDB shell version: 2.6.12
connecting to: 127.0.0.1:9005/test
mongos> sh.addShard("repSetA/lparcmongo:9005") <- Replica Set Name / one of the members : Port number
{ "shardAdded" : "repSetA", "ok" : 1 }
mongos> sh.addShard("repSetB/lpardmongo:9005") <- Replica Set Name / one of the members : Port number
{ "shardAdded" : "repSetB", "ok" : 1 }
mongos> sh.enableSharding("ShardDB") <- Create Sharded DB
{ "ok" : 1 }
mongos> sh.shardCollection("ShardDB.shardCollection",{shardKey:1}) <- Create a sharded Collection using Sharded Key.
{ "collectionsharded" : "ShardDB.shardCollection", "ok" : 1 }
mongos> show dbs
ShardDB 0.078GB
admin (empty)
config 0.016GB
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"version" : 4,
"minCompatibleVersion" : 4,
"currentVersion" : 5,
"clusterId" : ObjectId("5ac7b86e1bf26be6f336303d")
}
shards:
{ "_id" : "repSetA", "host" : "repSetA/lparcmongo:9005,lparcmongo:9006" }
{ "_id" : "repSetB", "host" : "repSetB/lpardmongo:9005,lpardmongo:9006" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "test", "partitioned" : false, "primary" : "repSetA" }
{ "_id" : "ShardDB", "partitioned" : true, "primary" : "repSetA" }
ShardDB.shardCollection
shard key: { "shardKey" : 1 }
chunks:
repSetA 1
{ "shardKey" : { "$minKey" : 1 } } -->> { "shardKey" : { "$maxKey" : 1 } } on : repSetA Timestamp(1, 0)
mongos>
Outcome
In the end, the shard controller will display something similar:
2018-06-07T15:14:13.627+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fa5c55b88e9e647af06 2018-06-07T15:14:13.874+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:19.877+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fabc55b88e9e647af07 2018-06-07T15:14:19.887+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:25.890+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fb1c55b88e9e647af08 2018-06-07T15:14:25.899+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:31.903+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fb7c55b88e9e647af09 2018-06-07T15:14:31.935+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:37.942+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fbdc55b88e9e647af0a 2018-06-07T15:14:37.980+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:43.284+0200 [LockPinger] cluster lparamongo:9005 pinged successfully at Thu Jun 7 15:14:43 2018 by distributed lock pinger 'lparamongo:9005/lparbmongo:9005:1528377223:1804289383', sleeping for 30000ms 2018-06-07T15:14:43.983+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fc3c55b88e9e647af0b 2018-06-07T15:14:43.991+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:49.994+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fc9c55b88e9e647af0c 2018-06-07T15:14:50.269+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:14:56.271+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fd0c55b88e9e647af0d 2018-06-07T15:14:56.279+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:15:02.282+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fd6c55b88e9e647af0e 2018-06-07T15:15:02.290+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' unlocked. 2018-06-07T15:15:08.293+0200 [Balancer] distributed lock 'balancer/lparbmongo:9005:1528377223:1804289383' acquired, ts : 5b192fdcc55b88e9e647af0f