Shulou(Shulou.com)06/02 Report--

Configuration Redis Master-Slave replication and Cluster configuration

1. Configure redis master-slave replication.

1.1. Application scenario

Generally speaking, to apply Redis to an engineering project, it is absolutely impossible to use only one Redis for the following reasons:

A) structurally, a single Redis server will have a single point of failure, and a single server needs to handle all the request load, which is stressful.

B) in terms of capacity, the memory capacity of a single Redis server is limited. Even if the memory capacity of a Redis server is 256g, you cannot use all the memory as Redis storage memory. Generally speaking, the maximum memory used by a single Redis should not exceed 20g.

1.2. Basic principles

The goods on e-commerce websites are generally uploaded at one time and browsed countless times, saying that the professional point is "read more and write less".

For this scenario, we can make the following architecture:

1.3. Detailed configuration

1) Plan the master and slave network information. Host 192.168.153.164 standby 192.168.153.165. Make sure the two machines are connected.

Drawing instructions

2) install redis and configure it. You can refer to the redis installation steps the day before yesterday.

A) modify the yum source and increase the yum configuration of redis

B) yum install epel-release-y yum install redis-y

C) modify the configuration file / etc/redis.conf

3) modify the standby configuration on the standby 192.168.153. Add the following configuration to the redis.conf of 165s

4) slaveof 192.168.153. 164 6379

5) Test effect

A) set the value chenjian=666 on the host

B) take the value get chenjian on the standby and display it normally.

C) Note: make sure the host starts first.

1.4. The characteristics of redis master-slave replication.

Master-slave replication allows multiple slave server to have the same database replica as master server. Here are some features of redis master-slave replication

A) master can have multiple slave

B) in addition to multiple slave connected to the same master, slave can also connect other slave to form a graph structure

C) Master-slave replication does not block master. That is, when one or more slave synchronizes data with master for the first time, master can continue to process requests from client. In contrast, when slave first synchronizes data, it blocks requests that cannot be processed by client.

D) Master-slave replication can be used to improve the scalability of the system. We can use multiple slave specifically for client read requests, for example, sort operations can be handled using slave. It can also be used for simple data redundancy.

E) you can disable data persistence on master by commenting out all save configurations in the master configuration file and then configuring data persistence only on slave.

two。 Configure redis Cluster

2.1. Application scenario

When the master / slave replication scenario cannot satisfy the single point of failure of the host, the cluster configuration needs to be introduced.

2.2. Basic principles

In the sentinel election mechanism, if half of the nodes find an abnormal node, they jointly decide to change the state of the abnormal node. If the node is the primary node, the corresponding standby node automatically replaces the primary node. Sentinel (Sentinel) is a high availability solution for Redis: a Sentinel system consisting of one or more Sentinel instances can monitor any number of master servers and all slave servers under these master servers, and automatically upgrade one of the slave servers under the offline master server to a new master server when the monitored master server goes offline.

2.3. Detailed configuration

1) step 1, plan the network.

A virtual machine is used to simulate 6 nodes and a machine 6 nodes to create a 3 master, 3 salve environment. The virtual machine is CentOS6.9 with ip address 192.168.153.164

2) step 2, download the source package of redis

Wget http://download.redis.io/releases/redis-3.2.11.tar.gz copies the redis-trib.rb in the package to the / usr/local/bin directory

3) step 3, create a Redis node

First create the redis_cluster directory on the 192.168.153.164 machine under the / usr/local directory

Mkdir redis_cluster

Under the redis_cluster directory, create a directory named 7001, 7002, 7003, 7004, 7005, 7006

Mkdir 7001 7002 7003 7004 7005 7006

And copy the redis.conf to these three directories. Modify the redis.conf before copying.

The redis.conf file is modified according to the following 8 items, and then copied to 6 different directories 7001, 7002, 7003, 7004, 7005, 7006.

Port 7000 / / Port 70007002 7003

Bind native ip / / default ip is 127.0.0.1 which needs to be changed to an ip accessible to other node machines, otherwise the corresponding port cannot be accessed when creating a cluster, and the cluster cannot be created.

Daemonize yes / / redis running in the background

Pidfile / var/run/redis_7000.pid / / pidfile files correspond to 7000Magi 7001jp7002

Cluster-enabled yes / / Open the cluster and remove the comment #

The configuration file of the cluster-config-file nodes_7000.conf / / cluster starts the automatic generation of 7000pr 7001pr 7002 for the first time

The cluster-node-timeout 15000 / / request timeout defaults to 15 seconds, which can be set by yourself.

Appendonly yes / / aof log is enabled if necessary. It records a log for each write operation.

4) step 4, start each node

Redis-server / usr/local/redis_cluster/7001/redis.conf

Redis-server / usr/local/redis_cluster/7002/redis.conf

Redis-server / usr/local/redis_cluster/7003/redis.conf

Redis-server / usr/local/redis_cluster/7004/redis.conf

Redis-server / usr/local/redis_cluster/7005/redis.conf

Redis-server / usr/local/redis_cluster/7006/redis.conf

Check node startup status

5) step 5, create a cluster

The command to create the cluster:

/ usr/local/bin/redis-trib.rb create-- replicas 1 192.168.153.164Viru 7002 192.168.153.164purl 7002 192.168.153.164VOL7003 192.168.153.164VERV 7004 192.168.153.164purl 7005 192.168.153.16415006

This error is that the operating system does not have ruby installed

Solution: install ruby

Yum-y install ruby ruby-devel rubygems rpm-build

Gem install redis reported an error

# # upgrading ruby

Gpg2-keyserver hkp://keys.gnupg.net-recv-keys D39DC0E3

Curl-L get.rvm.io | bash-s stable

Source / usr/local/rvm/scripts/rvm

Rvm list known

Rvm install 2.3.3

Rvm use 2.3.3

Rvm use 2.3.3-default

Ruby-version

Execute it again, success!

Gem install redis

6) verify the cluster

Redis-cli-c-h 192.168.153.164-p 7001, where-c indicates that the redis,-h is connected in a cluster mode to specify the ip address, and-p specifies the port number

Save the data, chenjian to the slot of 12007, and the node of 12007 is the node corresponding to port 7003.

Get chenjian on other nodes, such as 7006.

When verifying that the primary node is abnormal, the standby node automatically replaces the primary node.

Kill the process corresponding to 7002, that is, let the master node 7002 exception and check whether 7005 is replaced as the master node.

2.4. The characteristics of the cluster (1) all redis nodes are interconnected with each other (PING-PONG mechanism), and the binary protocol is used internally to optimize the transmission speed and bandwidth; (2) the fail of the node takes effect only when the failure is detected by more than half of the nodes in the cluster; (3) the client is directly connected to the redis node and does not need an intermediate proxy layer. The client does not need to connect all the nodes in the cluster, but any available node in the cluster. (4) redis-cluster maps all physical nodes to [0-16383] slot (hash slots), and cluster is responsible for maintaining nodeslotvalue.

2.5. Fault tolerance in cluster election

(1): when is the entire cluster unavailable (cluster_state:fail)? A: if any master of the cluster is down, and there is no slave in the current master. When a cluster enters the fail state, it can also be understood as entering the fail state when the cluster's slot mapping [0-16383] is incomplete. Ps: redis-3.0.0.rc1 is added to the cluster-require-full- coverage parameter. If it is disabled by default, it fails to enable the cluster compatibility part. B: if more than half of the cluster master dies, no matter whether or not any slave cluster enters the fail state. Ps: when the cluster is not available, all operations on the cluster are not available. A ((error) CLUSTERDOWN The cluster is down) error was received.

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