introduction to redis
TRANSCRIPT
Agenda● What is Redis?● Features● Persistence● Data types● Commands● Publish / Subscribe● Sort● Transactions● Replication● Cluster 2
What is Redis?● Data structure server● In-memory Key-Value store
○ it is also persistent!● Open source, BSD licensed
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Features● Abstract data types● Atomic operations● Service-side operations● Transactions● Pub/Sub● Lua scripting● TTL (Time-to-Live)● Master-Slave asynchronous replication● Atomic Failover
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Persistence● Can be optionally disabled● RDB file
○ Synchronized to disk (eventually or immediately)○ Use SAVE or BGSAVE command to create a snapshot manually.
● Data is dumped or written as a append-only change-log (AOF)● AOF mode supports transactional disk write● Default config:
○ Save after 900 sec (15 min) if at least 1 key changed.○ Save after 300 sec (5 min) if at least 10 keys changed.○ Save after 60 sec if at least 10000 keys changed.
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Data Types● String (binary safe)● Lists (linked lists)● Sets● Sorted sets (with scores)● Hashes (<String, String>)● Bitmaps (Bit arrays)
Note: The type of a value determines what operations (called commands) are available for the value itself.
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Redis keys● Binary safe● Empty string is valid key● Very long key is a bad idea● Very short key is [often] a bad idea
○ u1000flw● Stick with a schema
○ user:1000:followers● Max allowed key size is 512 MB.
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Basic commands● SET key value [EX seconds] [PX milliseconds] [NX|XX]
○ MSET key value [key value ….]● GET key
○ MGET key [key ….]● INCR/DECR key● INCRBY/DECRBY key increment● DEL key● EXISTS key● EXPIRE key seconds● TTL/PTTL key● TYPE key● MONITOR● HELP command
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Atomic Operations● GETSET key value
○ Puts a new value, retrieving old one.● SETNX key value
○ Sets a value only if it does not exist.
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Strings● Simplest type of value in Redis● redis-cli> SET mykey value
OK
● redis-cli> GET mykey“value”
● redis-cli> SET foo 110OK
● redis-cli> INCR bar(integer) 1
● redis-cli> INCRBY foo 50(integer) 160
● Max allowed value size is 512 MB.
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● Implemented by Linked List● Push and pop at both sides● BLPOP: Blocking POP
LPOPBLPOP
Lists
A B C DLPUSH RPUSH
RPOPBRPOP
LRANGE
LINDEXLSETLREM...
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Sets
A, B, CSADD
B, C, DSREMSPOP
SISMEMBER
B, CSINTER
A, B, C, DSUNION
ASDIFF D
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● Same as sets, but with score per element
Sorted Sets
foo | 12.1 bar | 14.3 baz | 17.87 qux | 30.9876ZADD key score memeber [score memeber
...]
ZRANGE key start stop [withscores]ZREVRANGE key start stop [WITHSCORES]ZRANGEBYSCORE key min max [WITHSCORES] [LIMIT offset count]ZREVRANGEBYSCORE key max min [WITHSCORES] [LIMIT offset count]
ZSCORE key memberZRANK key member
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Hashes● redis-cli> HSET foo bar 1
(integer) 1
● redis-cli> HSET foo baz 2(integer) 1
● redis-cli> SET foo foo foo(integer) 1
● redis-cli> HGETALL foo1) "bar"
2) "1"
3) "baz"
4) "1"
5) "foo”
6) "foo"
● redis-cli> HINCRBY foo bar 1(integer) 2
● redis-cli> HGET foo bar“2”
● redis-cli> HKEYS foo1) "bar"
2) "baz"
3) "foo"
● redis-cli> HSCAN foo 0 MATCH *ba*1) "0"
2)
1) "bar"
2) "3"
3) "baz"
4) "1" 14
Publish / Subscribe (PubSub)● Clients can subscribe to channels or patterns.● Subscribing is O(1), Posting message is O(N)● Chats, Comet Apps, Real time analytics and etc.
On Client 1:
redis-cli> subscribe feed:foo feed:bar feed:baz
Reading messages...
On Client 2:
redis-cli> publish feed:foo “hello world!”
(integer) 1
On Client 1:
Reading messages...
1) "message"
2) "feed:foo"
3) "hello world!"
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Sort● SORT key
○ [BY pattern]○ [LIMIT offset count]○ [GET pattern [GET pattern ...]]○ [ASC|DESC]○ [ALPHA]○ [STORE destination]
● By default, sorting is numeric and elements compared as double.● Use the ALPHA modifier to sort string list lexicographically (UTF-8 aware).● Result can be stored as a list.
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Transactions● MULTI, [commands], EXEC● All commands are executed after EXEC.● redis-cli> MULTI
OK
● redis-cli> SET foo barQUEUED
● redis-cli> INCRBY num 1 QUEUED
● redis-cli> EXEC1) OK
2) (integer) 1
● DISCARD for discarding a transaction● WATCH for locking keys
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Replication● Asynchronous, Non-Blocking Replication● Turn on persistence in the Master or avoid restarting automatically.● 64GB of memory i.e., Only 64GB of data
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Redis Master Server
Redis Slave ServerRedis Slave ServerRedis Slave Server
Cluster● Version 3.0 or higher. (Current stable version is 2.8)● Automatically split your dataset among multiple nodes.● Continue operations when a subset of the nodes are experiencing failures.● 10 clustered computers with each 64GB of RAM, store 640GB of data.
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Where Can I Learn More?● redis.io● redis.io/topics/quickstart● try.redis.io
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