Shulou(Shulou.com)06/01 Report--

I. on MongoDB replication sets

1. What is a replication set

Replication sets are additional replicas of data, the process of synchronizing data across multiple servers, providing redundancy and increasing data availability, through which hardware failures and interrupted services can be restored.

The advantages of replication sets are as follows:

 makes data more secure

 makes data availability (7 * 24)

 disaster recovery

 non-downtime maintenance (such as backup, index reconstruction, failover)

 read scaling (additional copy reads)

The  replica set is transparent to the application

2. The working principle of replication set

The replication set of MongoDB requires at least two nodes. One of them is the master node (primary), which is responsible for processing the client's requests, and the rest is the slave node (Secondary), which is responsible for replicating the data on the master node.

The common collocation of each node in MongoDB is: one master, one slave or one master and multiple slaves. The master node records all the operations on it to the oplog, periodically polls the slave node to obtain these operations, and then performs these operations on its own data copy, so as to ensure that the data of the slave node is consistent with that of the master node.

The master-slave replication structure diagram is as follows:

Replication sets have the following characteristics:

 N-node cluster

Any node of the  can be used as the primary node

 all writes are on the primary node

 automatic failover

 automatic recovery

II. MongoDB replication set deployment

1. Configure the yum source

Vi / etc/yum.repos.d/CentOS-Base.repo / / Last line increase

[mongodb-org]

Name=MongoDB Repository

Baseurl= https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/3.6/x86_64/

Gpgcheck=1

Enabled=1

Gpgkey= https://www.mongodb.org/static/pgp/server-3.6.asc

2. Install and configure mongodb

Yum install-y mongodb-org / / install vi / etc/mongod.conf / / modify listening address and port

Open the replication module

3. Create multiple real columns

Mkdir-p / data/mongodb/mongodb {2rec 3j 4} / / create a data directory cd / datamkdir logs touch logs/mongodb {2pr 3 4} .log / / create log file cd logs/chmod 777 * .log / / grant permission to cp-p / etc/mongod.conf / etc/mongod2.conf / / copy the main configuration file cp-p / etc/mongod.conf / etc/mongod3.confcp-p / etc/mongod.conf / etc/mongod4.confvi / etc/mongod2.conf / / modify the main configuration file in turn (note that the name of the file is different)

Mongod-f / etc/mongod.conf / / enter the corresponding real column mongod-f / etc/mongod2.confmongod-f / etc/mongod3.confmongod-f / etc/mongod4.conf

4. Configure the replication set of three nodes

Mongo / / enter the library cfg= {"_ id": "kgcrs", "members": [{"_ id": 0, "host": "192.168.80.100 kgcrs 27017"}, {"_ id": 1, "host": "192.168.80.100 id 27018"}, {"_ id": 2, "host": "192.168.80.100 kgcrs 27019"}, {"_ id": 3 "host": "192.168.80.100 cfg 27020]} / / add the other three nodes to the replication set rs.status (cfg) / / initialize the replication set configuration rs.status () / / View the status of the replication set

Rs.remove ("192.168.80.183 27020") / / Delete node rs.add ("192.168.80.183 VR 27020") / / add nodes

5. Verify the replication set

Use testdb.a.insert ({"id": 1, "name": "jack"}) db.a.find ()

Go to other nodes to check verification in turn.

Mongo-port 27018show dbs

III. MongoDB replication switching

1. Automatic failover

Mongod-f / etc/mongo.conf-- shutdown / / simulates the simulated point of failure mongdo-port 27018 / / enters the new master node rs.status () / / to view the replication set status

2. Switch manually

Mongdo-port 27018 / / enter the master node rs.stepDown (60J30) / / hand over the location of the master node rs.status () / / View status

Rs.freeze (30) / / suspend for 30s not to participate in the election. There must be an arbitration node, which is verified in the copy election below.

IV. MongoDB duplicates elections

1. Restore the virtual machine and repeat the above installation of mongoDB and add multiple instances

2. Configure three replication nodes

Mongo / / enter cfg= {"_ id": "kgcrs", "members": [{"_ id": 0, "host": "192.168.80.100 priority 27017", "priority": 100}, {"_ id": 1, "host": "192.168.80.100 id 27018", "priority": 100}, {"_ id": 2, "host": "192.168.80.100 priority 27019", "priority": 0}, {"_ id": 3) "host": "192.168.80.100 true 27020", "arbiterOnly": true}]} / / specify the attribute to which the replication node is assigned (priority is 100: standard node Priority is 0: passive node, arbiterOnly: arbitration node) rs.initiate (cfg) / / initialization configuration rs.isMaster () / / View node attributes

Use localshow collections / / View the collection

Db.oplog.rs.find () / / View log all operations

3. Simulation of faecal node failure

Mongod-f / etc/mongod.conf-- shutdown / / Simulation Standard Node 1 failure mongo-- port 27018 / / enter the second standby node to verify whether it is elected as the primary node

Mongod-f / etc/mongod2.conf-- shutdown / / simulates standard node 2 failure mongo-- port 27019 / / enters the passive node verification, and the passive node cannot become the primary node

4. Allow data to be read from nodes

Data cannot be viewed from the slave node

Rs.slaveOk () / / allow data to be read from nodes show dbs; / / allow data to be read from nodes by default

5. View replication status information

Rs.help () / / View rs.printReplicationInfo () / / View replication set information

Rs.printSlaveReplicationInfo () / / View the status of the slave node

Note: there is no arbitration node, which means that the arbitration node does not have the ability to copy data.

6. Change the oplog size

Use localdb.oplog.rs.stats () / / View the status of the operation replication operation

Method 1:

Use admin / / enter the management library db.shutdownServer () / / close the login replication set related startup parameter vi / etc/mongod.conf / / modify the port to 27028 and note the replication set parameter mongod-f / etc/mongod.conf / / single instance startup mongodump-- port 27028-- db local-- collection 'oplog.rs' / / backup operation log mongo-- port 27028 > use local > db.oplog.rs.drop () / / Delete the log file > db.runCommand ({create: "oplog.rs" Capped: true, size: (2 * 1024 * 1024 * 1024)}) / / recreate the log file and specify the size > use admin > db.shutdownServer () / / turn off the node service

Method 2:

Vi / etc/mongod.conf / / modify port back to 27018 to open the replication set parameter to specify the size of the replication set

Mongod-f / etc/mongod.conf / / restart mongo / / enter the instance verification

7. Give up being elected to form a new and valid election

Mongo-port 27018 / / enter the primary node rs.stepDown () / / give up the right to vote

Rs.status () / / another standard node is effectively elected as the primary node

5. Deploy authentication copy vi / etc/mongod.confvi / etc/mongod2.confvi / etc/mongod3.confvi / etc/mongod4.conf / / open the security authentication module in turn

Cd / usr/bin/ enter bin directory echo "kgcrskey" > kgcrskey1 / / create authentication file echo "kgcrskey" > kgcrskey2echo "kgcrskey" > kgcrskey3echo "kgcrskey" > kgcrskey4chmod 600 kgcrskey {1.. 4} / / change permissions

Restart the four instances in turn

Enter the primary node

Kgcrs:PRIMARY > show dbs # cannot view the database

Kgcrs:PRIMARY > rs.status () # unable to view replication set

Kgcrs:PRIMARY > use admin # identity login authentication

Kgcrs:PRIMARY > db.auth ("root", "123")

Kgcrs:PRIMARY > rs.status () # you can view the database

Kgcrs:PRIMARY > show dbs # can view replication sets

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