A single node instance
Single node instance is relatively simple, usually do a test, write a small program if you need to use cache, start one
Redis is still very easy, as a key/value database can also be competent
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2. Master/Slaver mode
Redis master/slave mode configuration
Master-slave mode:
In the master-slave mode of Redis, the slave node asynchronously replicates data from the master node, master
Nodes provide read and write services, while slave nodes only provide read services (this is the default configuration and can be modified by modifying the configuration file)
Slave-read-only Control). A master node can have multiple slave nodes. To configure a slave node, only the
Conf file to slaveof master-ip master-port.
There are three ways to enable master/slave replication on a secondary node:
The configuration file
Add: slaveof<masterip><masterport> to the configuration file of the slave server
Start the command
Redis-server: slaveof<masterip><masterport>
Client command
After the Redis server is started, run slaveof<masterip><masterport> on the client
The instance becomes a slave node.
The above three methods are equivalent. The following uses the client command as an example to look at Redis after slaveof is executed
Changes to primary and secondary nodes.
In this example, a master node has two slave nodes
Configuration:
1, CD/usr/local/redis/redis – 4.0.2
Switch to the current Redis installation path
2, the mkdir config
Create a new folder to store the redis configuration files
3. In config, create three configuration files as follows:
cd config
vi master-6739.conf
The bind 0.0.0.0
port 6379
logfile “6379.log”
dbfilename “dump-6379.rdb”
daemonize yes
rdbcompression yes
Vi slave – 6380. Confbind 0.0.0.0
port 6380
logfile “6380.log”
dbfilename “dump-6380.rdb”
daemonize yes
rdbcompression yes
Slaveof 192.168.81.135 6379
vi slave-6381.conf
The bind 0.0.0.0
port 6381
logfile “6381.log”
dbfilename “dump-6381.rdb”
daemonize yes
rdbcompression yes
Slaveof 192.168.81.135 6379
Master-6739. Conf indicates the configuration file of the master node, slave-6380.conf indicates the configuration file of the slave node
Use: slaveof in the slave node configuration file to specify the master node
4. Start three REids services
[root @ localhost redis - 4.0.2]# ./src/redis-server config/master-6379.conf [root @ localhost redis - 4.0.2]# ./src/redis-server config/slave-6380.conf [root @ localhost redis - 4.0.2]# ./src/redis-server config/slave-6381.confCopy the codeCheck out the Redis service
Test master/slave mode:
A, first connect three Redis services respectively, obtain the value of key as name, and specify the Redis service connected to that port through -p
[root @ localhost redis - 4.0.2]# ./src/redis-cli -p 6379
127.0.0.1:6379> get name
(nil)
[root@localhost redis-4.0.2]# ./src/redis-cli -p 6380
127.0.0.1:6380> get name
(nil)
[root@localhost redis-4.0.2]# ./src/redis-cli -p 6381 127.0.0.1:6381 > get name (nil)The values obtained are nullCopy the codeB, set a key for the master node
[root @ localhost redis - 4.0.2]# ./src/redis-cli -p 6379127.0.0.1:6379 >setName cmy OK 127.0.0.1:6379> get name"cmy"Copy the codeC. The slave node directly reads the value whose key is name
[root @ localhost redis - 4.0.2]# ./src/redis-cli -p 6380127.0.0.1:6380 > get the name"cmy"[root @ localhost redis - 4.0.2]# ./src/redis-cli -p 6381127.0.0.1:6381 > get the name"cmy"Copy the codeD. The slave node only provides read services and cannot perform write operations
127.0.0.1:6381 >set age 23
(error) READONLY You can't write against a read only slave.Copy the codePay attention to
When using master-slave mode, pay attention to the persistence operation of the Matser node, and the details of the situation when the matser node does not use persistence
If the server is down and the service is automatically restarted, data on the secondary server will be lost.
First, disable the matser service persistence
127.0.0.1:6379 > CONFIG SET save"" Copy the codeOK
Set a value on the master node
127.0.0.1:6379 >set age 23 Copy the codeOK
The slave node can get the age value
127.0.0.1:6380 > get the age"23" Copy the codeDisable the master node service
127.0.0.1:6379 > shutdown not connected >Copy the codeThe slave node can still get the age value
127.0.0.1:6380 > get the age"23" Copy the codeWhen the master service is restarted, the age value cannot be obtained
[root @ localhost redis - 4.0.2]# ./src/redis-server config/master-6379.conf [root @ localhost redis - 4.0.2]# ./src/redis-cli -p 6379 127.0.0.1:6379 > get the age (nil)Copy the codeThe value of age obtained by the slave node is null, causing data loss
[root @ localhost redis - 4.0.2]# ./src/redis-cli -p 6380 127.0.0.1:6380 > get the age (nil)Copy the codeCause of data loss: After the master service is suspended, the slave node communicates with the master node after the service is restarted
A complete resynchronization operation, so since the master node is not persisted, the data on the slave node will also be
Lost. Therefore, when configuring the master/slave mode of Redis, you should turn on the persistence function of the master server.
At this point, the Master-slave mode of Redis is complete
Talk about what I see as the need for a master-slave model:
One of the purposes of the master-slave mode is to back up data so that when a node is damaged (i.e. unrecoverable hardware damage), the data is stored
Because there is backup, it can be easily restored.
Another function is load balancing. All clients accessing a node will definitely affect the working efficiency of Redis
Later, the query operation can be done by querying the slave node.
Essential understanding of the master-slave pattern (conclusions have been verified and can be verified by yourself) :
A Master can have multiple Slaves
By default, the master node can perform read and write operations, while the slave node can only perform read operations and write operations are prohibited
Do not modify the configuration to support write operations on the slave node. For one reason, data written to the slave node will not be synchronized to other nodes
Node; Cause two: After the master node modifies the same data, the slave node overwrites the data
If the slave node is down, the read and write of other slave nodes and master nodes are not affected. After the slave node is restarted, data is removed from the slave node
The master node is synchronized
If the master node is down, the read on the slave node is not affected. Redis no longer provides the write service and the master node is started
After Redis will provide external write services again.
If the master node fails, the slave node does not select another master
For example, if there is a password on the master node:
The client needs a password to access the master
The password is required to enable the slave service, which can be configured in the configuration
The client does not need a password to access the slave
Disadvantages of master and slave nodes
The disadvantages of master-slave mode can be seen from the above description:
When the master node is down, Redis cannot provide write services because the remaining slaves cannot become masters
This disadvantage impact is very big, especially for the production environment, is not a moment to stop the service, so the general health
The production environment is not just a master-slave model. Hence the following Sentinel model. 3. Sentinel model
The Redis Sentry mode, in popular parlour, is a “sentry robot”, and phase the “sentry robot”
With the right configuration, this “robot” can work 24 hours a day, it can automatically help you do some things, such as monitoring
Control, remind, automatic troubleshooting and so on.
Redis – sentinel profile
Redis-sentinel is the author of Redis, Antirez, because the Redis cluster is used by large companies, each company needs to write its own cluster management tool, so Antirez spent several weeks to write redis-Sentinel.
Redis Sentinel system is used to manage multiple Redis servers (instance), and Redis Sentinel provides high availability for Redis. Use the Sentinel pattern to create a Redis deployment that can handle various failures without human intervention.
The system performs the following three tasks:
Monitoring: Sentinel continuously checks whether your primary and secondary servers are allowed to run properly.
Notification: Sentinel can use the API to send notifications to managers or other applications when a monitored Redis server has a problem.
Automatic failover: (1) When a primary server does not work properly, Sentinel is enabled
Starting an automatic failover operation, which upgrades one of the secondary servers of the failed master to the new master,
And make the other secondary servers of the failed master to replicate the new master server; (2) The client fails to connect to the master server
The cluster also returns the address of the new master server to the customer service, so the cluster can use the new master server instead of failing
The server.
Distributed characteristics of Sentinel
Redis Sentinel is a distributed system,
You can run multiple Sentinel processes in a schema that use gossip Protocols to receive information about whether the main server is offline, Agreement Protocols are used to determine whether automatic failover is performed and which slave server is selected as the new master server.
A single Sentinel process is not reliable to monitor the Redis cluster, and when the Sentinel process goes down (sentinel itself has a single point of failure) the entire cluster system will not behave as expected. So it is necessary to put
Sentinel cluster, which has several benefits:
- Some Sentinel processes are down, but the redis cluster can still be switched over.
- If there is only one Sentinel process, redis will not be implemented if the process runs incorrectly or if the network is clogged
Active/standby cluster switchover (single point);
If there are multiple Sentinels, a Redis client can connect to any sentinel at will to get information about the redis cluster
A robust deployment requires at least three sentinel instances.
The three sentinel instances should be placed on computers or virtual machines that the customer has identified as failing in a separate way. Different physics, for example
Machines or VMS in different availability zones. This explanation is a machine to build, and multi-level background is a truth
Recently, I came into contact with the construction of Redis for project requirements. I simply recorded the pits encountered in the construction process
The overall configuration
192.168.1.100:6379 -> master
192.168.1.101:6379 -> slave
192.168.1.102:6379 -> slave
192.168.1.100:26379 -> sentinel
192.168.1.101:26379 -> sentinel
192.168.1.102:26379 -> sentinel Copy the codeSet up steps
1. Install redis
# decompression
tar -xvf /usr/local/ redis - 3.2.11. Tar. Gz mkdir -p/usr /local/redis/bin
cp
/usr/local/redis/src/{redis-benchmark,redis-check-aof,redis-check-rdb,redis-cli,redis-sentinel,redi
s-server,redis-trib.rb} /usr/local/redis/bin
mkdir -p /u01/redis/{6379/{log,data,pid,conf},26379/{log,data,pid,conf}
Add environment variables
echo "export PATH=/usr/local/redis/bin:$PATH" >> /etc/profile
source /etc/profile Copy the code2. Configure redis – 6379
The redis node collocation base is as follows, and cp is divided into three virtual machines
/u01/redis/6379/conf/redis_6379.conf
bind 0.0.0.0
protected-mode no
daemonize yes
pidfile "/u01/redis/6379/pid/redis_6379.pid"
port 6379
tcp-backlog 511
timeout 0tcp-keepalive 0
loglevel notice
logfile "/u01/redis/6379/log/redis_6379.log"
databases 16
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename "dump.rdb"
dir "/u01/redis/6379/data"slave-serve-stale-data yes slave-read-only yes repl-diskless-sync no repl-diskless-sync-delay 5 repl-disable-tcp-nodelay no slave-priority 100 min-slaves-to-write 1 min-slaves-max-lag 10 appendonly no appendfilename"appendonly.aof"appendfsync everysec no-appendfsync-on-rewrite no auto-aof-rewrite-percentage 100 auto-aof-rewrite-min-size 64mb aof-load-truncated yes lua-time-limit 5000 slowlog-log-slower-than 10000 slowlog-max-len 128 latency-monitor-threshold 0 notify-keyspace-events""
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
list-max-ziplist-entries 512 Copy the codeStart the service
Run this command on three VMS
redis-server /u01/redis/6379/conf/redis_6379.conf Copy the codeEstablish a master-slave relationship
# in 192.168.1.101Redis -cli -p 6379 SLAVEOF 192.168.1.100 6379# in 192.168.1.102Redis -cli -p 6379 SLAVEOF 192.168.1.100 6379 View Replication 192.168.1.101:6379> Info Replication# Replication role:master connected_slaves:2 min_slaves_good_slaves:2 = 192.168.1.102 slave0: IP and port = 6379, state = online, offset = 9577826, lag = 1 = 192.168.1.103 slave1: IP and port = 6379, state = online, offset = 9577965, lag = 0 master_repl_offset: 9577965 repl_backlog_active: 1 Repl_backlog_size :1048576 repl_backlog_first_byte_offset:8529390 Repl_backlog_HISTlen :1048576 192.168.1.102:6379> Info replication# Replication Role :slave master_host:192.168.1.101 master_port:6379 master_link_status:up master_last_io_SECONds_ago :0 master_sync_in_progress:0 slave_repl_offset:9600220 slave_priority:100 slave_read_only:1 connected_slaves:0 min_slaves_good_slaves:0 master_repl_offset:0 repl_backlog_active:0 repl_backlog_size:1048576 Repl_backlog_first_byte_offset :0 repl_backlog_HISTlen :0 192.168.1.103:6379> Info replication# Replication Role :slave master_host:192.168.1.101 master_port:6379 master_link_status:up master_last_io_SECONds_ago :0 master_sync_in_progress:0 slave_repl_offset:9612675slave_priority:100 slave_read_only:1 connected_slaves:0 min_slaves_good_slaves:0 master_repl_offset:0 repl_backlog_active:0 repl_backlog_size:1048576 repl_backlog_first_byte_offset:0 repl_backlog_histlen:0Copy the code3. The sentinel – 6379 configuration
The sentinel node collocation base is as follows, and cp is divided into three virtual machines
/u01/redis/26379/conf/sentinel_26379.conf Copy the codeSentinel Monitor myMaster monitors the master node in Redis, that is, 192.168.1.100
This file is the same on all three machines
port 26379
bind 0.0.0.0
daemonize yes
protected-mode no
dir "/u01/redis/26379/tmp"
logfile "/u01/redis/26379/log/sentinel_26379.log"Sentinel Monitor MyMaster 192.168.1.100 6379 1Copy the codeWaiting to start after the observation/u01 / redis / 26379 / conf/sentinel_26379. Conf file changes
Run the info sentinel command to check the sentinel status
Redis -cli -h 192.168.1.100 -p 26379 info sentinel# Sentinel sentinel_masters:1 sentinel_tilt:0 sentinel_running_scripts:0 sentinel_scripts_queue_length:0 Sentinel_simulate_failure_flags: 0 master0: name = zhuanche01, status = ok, address = 192.168.1.100:6379, slaves = 2, sentinels = 3Copy the codeconclusion
When I was setting up, I encountered a problem with sentinel on 192.168.1.101 and 192.168.1.102.
It turns out there was no monitoring master
And then there’s the problem of looking at the log
The emergence of cluster is to solve the problem of limited capacity of single Redis and allocate Redis data according to certain rules
To multiple machines. Some understanding of cluster:
Cluster can be said to be the combination of Sentinel and master-slave mode. Through cluster, the master-slave and master re-selection can be realized
Yes, so if you configure two replicas and three shards, you need six Redis instances.
Because Redis data is allocated to different machines in the cluster according to certain rules, it can be added when the amount of data is too large
Machine capacity expansion
This mode is suitable for large data cache requirements, and sentinel can be used when the data volume is not large.
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