从图中可以看到有四个组件：mongos、config server、shard、replica set。
mongos，数据库集群请求的入口，所有的请求都通过mongos进行协调，不需要在应用程序添加一个路由选择器，mongos自己就是一个请求分发中心，它负责把对应的数据请求请求转发到对应的shard服务器上。在生产环境通常有多mongos作为请求的入口，防止其中一个挂掉所有的mongodb请求都没有办法 *** 作。
config server，顾名思义为配置服务器，存储所有数据库元信息（路由、分片）的配置。mongos本身没有物理存储分片服务器和数据路由信息，只是缓存在内存里，配置服务器则实际存储这些数据。mongos第一次启动或者关掉重启就会从 config server 加载配置信息，以后如果配置服务器信息变化会通知到所有的 mongos 更新自己的状态，这样 mongos 就能继续准确路由。在生产环境通常有多个 config server 配置服务器，因为它存储了分片路由的元数据，防止数据丢失！
shard，分片（sharding）是指将数据库拆分，将其分散在不同的机器上的过程。将数据分散到不同的机器上，不需要功能强大的服务器就可以存储更多的数据和处理更大的负载。基本思想就是将集合切成小块，这些块分散到若干片里，每个片只负责总数据的一部分，最后通过一个均衡器来对各个分片进行均衡（数据迁移）。
replica set，中文翻译副本集，其实就是shard的备份，防止shard挂掉之后数据丢失。复制提供了数据的冗余备份，并在多个服务器上存储数据副本，提高了数据的可用性， 并可以保证数据的安全性。
仲裁者（Arbiter），是复制集中的一个MongoDB实例，它并不保存数据。仲裁节点使用最小的资源并且不要求硬件设备，不能将Arbiter部署在同一个数据集节点中，可以部署在其他应用服务器或者监视服务器中，也可部署在单独的虚拟机中。为了确保复制集中有奇数的投票成员（包括primary），需要添加仲裁节点做为投票，否则primary不能运行时不会自动切换primary。
简单了解之后，我们可以这样总结一下，应用请求mongos来 *** 作mongodb的增删改查，配置服务器存储数据库元信息，并且和mongos做同步，数据最终存入在shard（分片）上，为了防止数据丢失同步在副本集中存储了一份，仲裁在数据存储到分片的时候决定存储到哪个节点。
系统系统 centos7
三台服务器：192.168.1.1/2/3
mongodb版本：3.2.8
服务器规划
端口分配：
mongos：27017
config：10004
shard1：10001
shard2：10002
shard3：10003安装mongodb
选择《OneinStack》数据库安装mongodb，注意版本为3.2.8
cat >> /etc/rc.local << EOF
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo never > /sys/kernel/mm/transparent_hugepage/defrag
EOF
三个节点都执行，如：192.168.1.1
mkdir /usr/local/mongodb/data/{configsvr,mongos,shard1,shard2,shard3}
mkdir /usr/local/mongodb/etc/keyfile
>/usr/local/mongodb/etc/keyfile/linuxeye
/usr/local/mongodb/etc/shard1.conf
systemLog:
destination: file
path: /usr/local/mongodb/log/shard1.log
logAppend: true
processManagement:
fork: true
pidFilePath: "/usr/local/mongodb/data/shard1/shard1.pid"
net:
port: 10001
storage:
dbPath: "/usr/local/mongodb/data/shard1"
engine: wiredTiger
journal:
enabled: true
directoryPerDB: true
operationProfiling:
slowOpThresholdMs: 10
mode: "slowOp"
#security:
# keyFile: "/usr/local/mongodb/etc/keyfile/linuxeye"
# clusterAuthMode: "keyFile"
replication:
oplogSizeMB: 50
replSetName: "shard1_linuxeye"
secondaryIndexPrefetch: "all"
/usr/local/mongodb/etc/shard2.conf
systemLog:
destination: file
path: /usr/local/mongodb/log/shard2.log
logAppend: true
processManagement:
fork: true
pidFilePath: "/usr/local/mongodb/data/shard2/shard2.pid"
net:
port: 10002
storage:
dbPath: "/usr/local/mongodb/data/shard2"
engine: wiredTiger
journal:
enabled: true
directoryPerDB: true
operationProfiling:
slowOpThresholdMs: 10
mode: "slowOp"
#security:
# keyFile: "/usr/local/mongodb/etc/keyfile/linuxeye"
# clusterAuthMode: "keyFile"
replication:
oplogSizeMB: 50
replSetName: "shard2_linuxeye"
secondaryIndexPrefetch: "all"
/usr/local/mongodb/etc/shard3.conf
systemLog:
destination: file
path: /usr/local/mongodb/log/shard3.log
logAppend: true
processManagement:
fork: true
pidFilePath: "/usr/local/mongodb/data/shard3/shard3.pid"
net:
port: 10003
storage:
dbPath: "/usr/local/mongodb/data/shard3"
engine: wiredTiger
journal:
enabled: true
directoryPerDB: true
operationProfiling:
slowOpThresholdMs: 10
mode: "slowOp"
#security:
# keyFile: "/usr/local/mongodb/etc/keyfile/linuxeye"
# clusterAuthMode: "keyFile"
replication:
oplogSizeMB: 50
replSetName: "shard3_linuxeye"
secondaryIndexPrefetch: "all"
/usr/local/mongodb/etc/configsvr.conf
systemLog:
destination: file
path: /usr/local/mongodb/log/configsvr.log
logAppend: true
processManagement:
fork: true
pidFilePath: "/usr/local/mongodb/data/configsvr/configsvr.pid"
net:
port: 10004
storage:
dbPath: "/usr/local/mongodb/data/configsvr"
engine: wiredTiger
journal:
enabled: true
#security:
# keyFile: "/usr/local/mongodb/etc/keyfile/linuxeye"
# clusterAuthMode: "keyFile"
sharding:
clusterRole: configsvr
/usr/local/mongodb/etc/mongos.conf
systemLog:
destination: file
path: /usr/local/mongodb/log/mongos.log
logAppend: true
processManagement:
fork: true
pidFilePath: /usr/local/mongodb/data/mongos/mongos.pid
net:
port: 27017
sharding:
configDB: 192.168.1.1:10004,192.168.1.2:10004,192.168.1.3:10004
#security:
# keyFile: "/usr/local/mongodb/etc/keyfile/linuxeye"
# clusterAuthMode: "keyFile"
分别启动mongo
/usr/local/mongodb/bin/mongod -f /usr/local/mongodb/etc/shard1.conf
/usr/local/mongodb/bin/mongod -f /usr/local/mongodb/etc/shard2.conf
/usr/local/mongodb/bin/mongod -f /usr/local/mongodb/etc/shard3.conf
/usr/local/mongodb/bin/mongo --port 10001
use admin
config = { _id:"shard1_linuxeye", members:[
{_id:0,host:"192.168.1.1:10001"},
{_id:1,host:"192.168.1.2:10001",arbiterOnly:true},
{_id:2,host:"192.168.1.3:10001"}
]
}
rs.initiate(config)
/usr/local/mongodb/bin/mongo --port 10002
use admin
config = { _id:"shard2_linuxeye", members:[
{_id:0,host:"192.168.1.1:10002"},
{_id:1,host:"192.168.1.2:10002"},
{_id:2,host:"192.168.1.3:10002",arbiterOnly:true}
]
}
rs.initiate(config)
/usr/local/mongodb/bin/mongo --port 10003
use admin
config = { _id:"shard3_linuxeye", members:[
{_id:0,host:"192.168.1.1:10003",arbiterOnly:true},
{_id:1,host:"192.168.1.2:10003"},
{_id:2,host:"192.168.1.3:10003"}
]
}
rs.initiate(config)
注：以上是配置rs复制集，相关命令如：rs.status()，查看各个复制集的状况
启动三台机器上的configsvr和mongos节点
/usr/local/mongodb/bin/mongod -f /usr/local/mongodb/etc/configsvr.conf
再分别启动
/usr/local/mongodb/bin/mongos -f /usr/local/mongodb/etc/mongos.conf
在192.168.1.1机器上配置shard分片
/usr/local/mongodb/bin/mongo --port 27017
use admin
db.runCommand({addshard:"shard1_linuxeye/192.168.1.1:10001,192.168.1.2:10001,192.168.1.3:10001"});
db.runCommand({addshard:"shard2_linuxeye/192.168.1.1:10002,192.168.1.2:10002,192.168.1.3:10002"});
db.runCommand({addshard:"shard3_linuxeye/192.168.1.1:10003,192.168.1.2:10003,192.168.1.3:10003"});
查看shard信息
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("5a55af962f787566bce05b78")
}
shards:
{ "_id" : "shard1_linuxeye", "host" : "shard1_linuxeye/192.168.1.1:10001,192.168.1.2:10001" }
{ "_id" : "shard2_linuxeye", "host" : "shard2_linuxeye/192.168.1.1:10002,192.168.1.2:10002" }
{ "_id" : "shard3_linuxeye", "host" : "shard3_linuxeye/192.168.1.1:10003,192.168.1.2:10003" }
active mongoses:
"3.2.8" : 3
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
查看分片状态
mongos> db.runCommand( {listshards : 1 } )
{
"shards" : [
{
"_id" : "shard1_linuxeye",
"host" : "shard1_linuxeye/192.168.1.1:10001,192.168.1.2:10001"
},
{
"_id" : "shard2_linuxeye",
"host" : "shard2_linuxeye/192.168.1.1:10002,192.168.1.2:10002"
},
{
"_id" : "shard3_linuxeye",
"host" : "shard3_linuxeye/192.168.1.1:10003,192.168.1.2:10003"
}
],
"ok" : 1
}
启用shard分片的库名字为'linuxeye'，即为库
use admin
mongos> sh.enableSharding("linuxeye")
{ "ok" : 1 }
db.runCommand({"enablesharding":"linuxeye"})
表分片：
db.runCommand({shardcollection:'linuxeye.LiveAppMesssage',"key":{"_id":1}})
查看状态
db.LiveAppMesssage.stats()
Thu Mar 1 09:28:08 CST 2018
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