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

Introduction to Redis

Redis (REmote DIctionary Server) is an open source log database written in ANSI C language, complies with BSD protocol, supports network, can be memory-based and persistent, and provides API in multiple languages. It is often called a data structure server because the value can be of types such as String, Map, list, sets, and sorted sets.

Redis features:

1. Data persistence is supported. The data in memory can be saved on disk and can be loaded and used again when rebooting.

2, not only supports simple key-value type data, but also provides storage of data structures such as list,set,zset,hash.

3. Support data backup, that is, data backup in master-slave mode

Redis advantages:

1. High reading and writing performance. The speed of reading is 110000 times / s and the speed of writing is 81000 times / s.

2, Rich data types-Redis supports Strings, Lists, Hashes, Sets and Ordered Sets data type operations for binary cases.

3. All operations of Atomic-Redis are atomic, and Redis also supports atomicity after several operations have been merged.

4, rich features-Redis also supports publish/subscribe, notification, key expiration, and so on.

(1) Redis installation

Environment:

Operating system: CentOS Linux release 7.2

The specific steps are as follows:

1. Download the installation package at the following address: https://redis.io/download

[root@localhost install] # wget http://download.redis.io/releases/redis-3.2.9.tar.gz [root@localhost install] # tar zxvf redis-3.2.9.tar.gz [root@localhost install] # mv redis-3.2.9/ usr/local/ [root@localhost install] # cd / usr/local/redis-3.2.9/ [root@localhost redis-3.2.9] # make MALLOC=libc

2. Start redis service. The / usr/local/redis-3.2.9/redis.conf configuration file is loaded by default.

[root@localhost redis-3.2.9] # cd src/ [root@localhost src] #. / redis-server 13796:C 07 Jun 04:40:46.590 # Warning: no config file specified, using the default config. In order to specify a config file use. / redis-server / path/to/redis.conf _. _ _.-``_ _'-. _ _.-```. `_. '' -. _ Redis 3.2.9 (00000000Universe 0) 64 bit.-``.- ```. ```\ / _., _'-. _ (.-`|` ) Running in standalone mode | `-. _`...-.`` -. _ |'`_. -'| Port: 6379 |` -. _ `. _ / _. -'| PID: 13796` -. _ `-. _`. / _. -'_. -'| `-. `-. _` -'_. | | `-. _` -. _ _. -'_. -'| http://redis.io `-. _` -. _ _. -'. | | `-. _` -. _ `. -'_. -'| |` -. _ `-. -'_. -'. _. -'`-. _`. -'. 13796:M 07 Jun 04:40:46.591 # WARNING: The TCP backlog setting of 511 cannot be enforced because / proc/sys/net/core/somaxconn is set to the lower value of 128.13796:M 07 Jun 04:40:46.591 # Server started Redis version 3.2.913796:M 07 Jun 04:40:46.591 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory=1' to / etc/sysctl.conf and then reboot or run the command' sysctl vm.overcommit_memory=1' for this to take effect.13796:M 07 Jun 04 etc/sysctl.conf and then reboot or run the command 40V 46.591 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > / sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your / etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.13796:M 07 Jun 04 DB loaded from disk: 0.000 seconds13796:M 07 Jun 0440 DB loaded from disk: 46.591 * The server is now ready to accept connections on port 6379

3. Use the client redis-cli to test the connection.

[appuser@localhost src] $cd. [appuser@localhost redis-3.2.9] $cd src/ [appuser@localhost src] $. / redis-cli 127.0.0.1 appuser@localhost src 6379 > set lqb barOK127.0.0.1:6379 > get lqb "bar" 127.0.0.1 appuser@localhost redis-3.2.9 6379 > pingPONG

(2) Redis configuration. Redis configuration can be viewed or set through the config command, or can be configured through redis.conf.

1, configure (config get config_setting_name) through the config command format:

127.0.0.1 config get loglevel1 6379) "loglevel" 2) "notice127.0.0.1:6379 > config get * # use * to get all configuration items 1)" dbfilename "2)" dump.rdb "3)" requirepass "4)" 5) "masterauth" 6) "7)" unixsocket "8)" 9) "logfile" 10) "" 11) "pidfile" 12) "13)" slave-announce-ip "14)" 15) "maxmemory" 16) "0" 17) "maxmemory-samples" 18) "5" 19) "timeout" 20) "0" 21) "auto-aof-rewrite-percentage" 22) "100" 23) "auto-aof-rewrite-min-size" 24) "67108864" 25) "hash-max-ziplist-entries" 26) "512" 27) "hash-max-ziplist-value" 28) "64" 29) "list-max-ziplist-size" 30) "2" 31) "list-compress-depth" 32) "0" 33) "set-max-intset-entries" 34) "512" 35) "zset-max-ziplist-entries" 36) "128" 37) "zset-max-ziplist-value" 38) "64" 39) "hll-sparse-max-bytes" 40) " 3000 "41)" lua-time-limit "42)" 5000 "43)" slowlog-log-slower-than "44)" 10000 "45)" latency-monitor-threshold "46)" 0 "47)" slowlog-max-len "48)" 6379 "49)" port "50)" 6379 "51)" tcp-backlog "52)" 511 "53)" databases "54)" 16 "55)" repl-ping-slave-period "56) "10" 57) "repl-timeout" 58) "60" 59) "repl-backlog-size" 60) "1048576" 61) "repl-backlog-ttl" 62) "3600" 63) "maxclients" 64) "10000" 65) "watchdog-period" 66) "0" 67) "slave-priority" 68) "slave-announce-port" 70) "0" 71) "min-slaves-to-write" 72) "0" 73) "min-slaves-max-lag" 74) "10" 75) "hz" 76) "10" 77) "cluster-node-timeout" 78) "15000" 79) "cluster-migration-barrier" 80) "1" 81) "cluster-slave-validity-factor" 82) "10" 83) "repl-diskless-sync-delay" 84) "5" 85) "tcp-keepalive" 86) "300" 87) " Cluster-require-full-coverage "88)" yes "89)" no-appendfsync-on-rewrite "90)" no "91)" slave-serve-stale-data "92)" yes "93)" slave-read-only "94)" yes "95)" stop-writes-on-bgsave-error "96)" yes "97)" daemonize "98)" no "99)" rdbcompression "99)" yes "101)" rdbchecksum "102)" Yes "103s)" activerehashing "104s)" yes "105s)" protected-mode "106cases)" yes "10108c)" no "1091103s)" repl-diskless-sync "110110l)" no "1111101c)" yes "113c)" aof-load-truncated "114)" yes "115)" maxmemory-policy "116)" noeviction "117)" loglevel "118)" Notice "supervised" 120) "no" 121) "appendfsync" 122) "everysec" 123) "syslog-facility" 124) "local0" 125) "appendonly" 126) "no" 127) "dir" 128) / usr/local/redis-3.2.9/src "129)" save "130)" 3600 1,300 100 60 10000 "client-output-buffer-limit" 33554432) "normal 000 slave 268435456 67108864 60 pubsub 33554432" 8388608 60133) "unixsocketperm" 13434) "slaveof" 13613) "notify-keyspace-events" 138) "139)" bind "140)" Edit configuration item syntax: config set config_setting_name new_config_value127.0.0.1:6379 > config set loglevel "notice" OK127.0.0.1:6379 > config get loglevel1) "loglevel" 2) "notice"

2the description of the configuration item for dint redis.conf is as follows:

1. Redis does not run as a daemon by default. You can use yes to enable the daemon daemonize no2. When Redis runs as a daemon, Redis writes pid to the / var/run/redis.pid file by default, and you can specify pidfile / var/run/redis.pid3 through pidfile. Specify the Redis listening port, and the default port is 6379. In a blog post, the author explained why 6379 is chosen as the default port, because 6379 has the number corresponding to MERZ on the phone button, and MERZ is taken from the name of Italian singer Alessia Merz port 63794. The bound host address bind 127.0.0.15. When the client is idle for how long to close the connection, if specified as 0, it means to turn off the function timeout 3006. Specifies the logging level. Redis supports a total of four levels: debug, verbose, notice, and warning. The default is verbose loglevel verbose7. The logging method defaults to standard output. If Redis is configured to run in daemon mode, and here the logging mode is configured as standard output, the log will be sent to / dev/null logfile stdout8. Set the number of databases. The default database is 0. You can use the SELECT command to specify the database id databases 169. 9 on the connection. Specify the length of time and the number of update operations to synchronize the data to the data file, and multiple conditions can be combined with three conditions provided in the save Redis default configuration file: save 9001 save 300 10 save 60 10000 represents 1 change in 900 seconds (15 minutes), 10 changes in 300 seconds (5 minutes), and 10000 changes in 60 seconds. 10. Specify whether to compress the data when storing to the local database. The default is that yes,Redis uses LZF compression. If you want to save CPU time, you can turn off this option, but it will cause the database file to become huge rdbcompression yes11. Specifies the local database file name, and the default value is dump.rdb dbfilename dump.rdb12. Specify the local database storage directory dir. / 13. Set the IP address and port of the master service when the machine is a slav service. When Redis starts, it automatically synchronizes data from master slaveof 14. When the master service sets password protection, the slav service connects to the master's password masterauth 15. 0. Set the Redis connection password. If the connection password is configured, the client needs to provide the password through the AUTH command when connecting to the Redis. By default, requirepass foobared16. Set the maximum number of client connections at a time. By default, there is no limit. The number of client connections that Redis can open at the same time is the maximum number of file descriptors that can be opened by Redis processes. If you set maxclients 0, there is no limit. When the number of client connections reaches the limit, Redis closes new connections and returns max number of clients reached error message maxclients 12817 to the client. Specify the maximum memory limit of Redis. Redis will load data into memory at startup. After reaching the maximum memory, Redis will first try to clear the expired or expiring Key. When this method is processed, the maximum memory setting will still be reached, and the write operation will no longer be performed, but the read operation can still be performed. Redis's new vm mechanism stores Key in memory and Value in swap area maxmemory 18. Specifies whether to log after each update operation. Redis writes data to disk asynchronously by default. If it is not enabled, it may result in data loss for a period of time in the event of a power outage. Because redis itself synchronizes data files according to the above save conditions, some data will only exist in memory for a period of time. The default is no appendonly no19. Specifies the update log file name, which defaults to appendonly.aof appendfilename appendonly.aof20. Specify the update log condition. There are three optional values: no: indicates that the operating system synchronizes the data cache to disk (fast) always: indicates that fsync () is manually called after each update operation to write data to disk (slow, secure) everysec: indicates synchronization once per second (eclectic, default) appendfsync everysec 21. Specify whether to enable the virtual memory mechanism, the default value is no, a brief introduction, the VM mechanism will be paged data storage, by the Redis less visited pages that is cold data swap to the disk, the visited pages are automatically swapped out to memory by the disk (in the following article I will carefully analyze the VM mechanism of Redis) vm-enabled no22. Virtual memory file path. Default is / tmp/redis.swap. Multiple Redis instances cannot share vm-swap-file / tmp/redis.swap23. All data larger than vm-max-memory is stored in virtual memory, no matter how small the vm-max-memory setting is, all index data is stored in memory (Redis's index data is keys), that is, when vm-max-memory is set to 0, all value actually exists on disk. The default value is 0 vm-max-memory 024. Redis swap files are divided into many page. An object can be stored on multiple page, but a page cannot be shared by multiple objects. Vm-page-size should be set according to the size of stored data. The author suggests that if many small objects are stored, the page size should be set to 32 or 64bytes. If you store large objects, you can use a larger page, or if you are not sure, use the default value of vm-page-size 3225. Set the number of page in the swap file, because the page table (a type of bitmap that indicates that the page is idle or used) is placed in memory, every 8 pages on disk will consume 1byte's memory. Vm-pages 13421772826. Set the number of threads to access the swap file, it is best not to exceed the number of cores of the machine, if set to 0, then all operations on the swap file are serial, which may cause a long delay. The default value is 4 vm-max-threads 427. Sets whether to merge smaller packets into a single packet when replying to the client. Default is to enable glueoutputbuf yes28. Specifies that when the number exceeds a certain number or the largest element exceeds a certain critical value, a special hashing algorithm hash-max-zipmap-entries 64 hash-max-zipmap-value 51229 is adopted. Specifies whether to activate reset hashing, which defaults to on (later on when introducing Redis's hashing algorithm) activerehashing yes30. Specify to include other configuration files that can use the same profile among multiple Redis instances on the same host, while each instance has its own specific configuration file include / path/to/local.conf

(3) redis data type

Redis supports five data types: string (string), hash (hash), list (list), set (collection) and zset (sorted set: ordered collection).

(1) string string:

The string in string is a sequence of bytes, which is the most basic type. You can understand it as the same type as Memcached, with a key corresponding to a value.

Strings in string are binary safe, which means that their length is not determined by any special termination character.

The string of redis can contain any data. Such as jpg images or serialized objects.

The string type is the most basic data type of Redis, and the maximum length of the string can store 512MB.

127.0.0.1 OK127.0.0.1:6379 6379 > set name "lqb" OK127.0.0.1:6379 > get name "lqb"

In the above example, we used Redis's SET and GET commands. The key is name and the corresponding value is lqb. Maximum 512MB can be stored in one key

(2) Hash (hash)

Redis hash is a collection of key-value pairs.

Redis hash is a mapping between string fields and string values, and hash is particularly suitable for representing objects.

127.0.1 username 6379 > hmset user username lqb password passwd123 OK127.0.0.1:6379 > hgetall user1) "username" 2) "lqb" 3) "password" 4) "passwd123"

In the example, we use the Redis HMSET, HGETALL commands, where user is the name of the key

Each hash can store 232-1 key-value pairs (more than 4 billion)

(3) list (list) The Redis list is a list of strings sorted in the order in which they are inserted. You can add an element to the head (left) or tail (right) of the list.

127.0.0.1) lpush runoob redis (integer) 1127.0.0.1 > lpush runoob mongodb (integer) 2127.0.0.1 > lpush runoob mysql (integer) 3127.0.0.1 > lrange runoob 0101) "mysql" 2) "mongodb" 3) "redis" 127.0.0.1 > lrange runoob 021) "mysql" 2) "mongodb" 3) "redis" 127.0.0.1 > lrange runoob 011) "mysql" 2) "mongodb"

Lists can store up to 232-1 elements (4294967295, each list can store more than 4 billion).

(4) set.

The Set of Redis is an unordered collection of type string.

The collection is implemented through a hash table, so the complexity of adding, deleting, and finding is all O (1).

Sadd command

Add a string element to the set collection corresponding to key, and successfully return 1. There is no return error if the element has already returned the set corresponding to 0MagneKey in the collection.

Grammar: sadd key member.

Redis 127.0.0.1 redis 6379 > sadd runoob redis (integer) 1redis 127.0.0.1 1redis 6379 > sadd runoob mongodb (integer) 1redis 127.0.0.1 1redis 6379 > sadd runoob rabitmq (integer) 1redis 127.0.0.1 sadd runoob rabitmq (integer) 0redis 127.0.0.1) smembers runoob1) "rabitmq" 2) "mongodb" 3) "redis"

Depending on the uniqueness of the elements in the collection, the second inserted element is ignored.

The maximum number of members in the collection is 4294967295 (each collection can store more than 4 billion members).

(5) zset (sorted set: ordered set) is a collection of characters that are not repeated. Redis zset, like set, is a collection of elements of type string, and duplicate members are not allowed.

The difference is that each element is associated with a score of type double. Redis sorts the members of the collection from small to large by scores. The members of the zset are unique, but the score can be repeated.

Zadd command format: zadd key score member

Add an element to the collection, and update the corresponding score if the element exists in the collection

Redis 127.0.0.1 redis 6379 > zadd runoob 0redis (integer) 1redis 127.0.0.1 integer 6379 > zadd runoob 0 mongodb (integer) 1redis 127.0.0.1 1redis 127.0.0.1 integer 1redis 127.0.1 1redis 6379 > zadd runoob 0 rabitmq (integer) 0redis 127.0.1 Suzhou 6379 > ZRANGEBYSCORE runoob 0 10001) "redis" 2) "mongodb" 3) "rabitmq"

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