Introduction to Redis and redis-cli

Redis is short for "Remote Dictionary Server"

Uses

----

- in-memory data structure store

- database

- cache

- message broker

Atomic Operations

-----------------

- appending to a string

- incrementing hash value

- pushing an element to a list

- computing set intersection

- union and difference

- getting the member with highest ranking in a sorted set

redis-cli

---------

- Can be run in command and interactive modes

- History is kept in ~/.rediscli_history

    * filename can be changed via  REDISCLI_HISTFILE environment variable

    * setting it to /dev/null will disable history

Command Mode

------------

Output	## human-readable if TTY is detected redis-cli incr mycounter ## raw output redis-cli incr mycounter > /tmp/output.txt ## forces raw output redis-cli --raw incr mycounter ## CSV output (can't be run on whole DB) redis-cli lpush mylist a b c d redis-cli --csv lrange mylist 0 -1
Connecting	## connects 127.0.0.1 at 6379 redis-cli ## connects to another host/port redis-cli -h redis15.localnet.org -p 6390 ping ## used for password protected instances redis-cli -a myUnguessablePazzzzzword123 ping ## uses a different database number (default is 0) redis-cli -n 4 incr a ## using a URI redis-cli -u redis://myPass123@redishost.com:16379/0 ping
Writing	## adds a key value pair redis-cli set A apple ## running same command overwrites previous value redis-cli set A anatomy ## getting input from others redis-cli -x set foo < /etc/services
Listing/ Displaying/ Querying	## prints server info redis-cli info ## replication commands redis-cli info replication redis-cli role ## prints value of a key redis-cli get food ## displays range of value only redis-cli getrange food 0 50
Batch Mode	## commands are executed in order as typed in the file $ cat /tmp/commands.txt set foo 100 incr foo append foo xxx get foo $ cat /tmp/commands.txt | redis-cli OK (integer) 101 (integer) 6 "101xxx" ## quotations can be used $ cat /tmp/commands.txt set foo "This is a single argument" strlen foo $ cat /tmp/commands.txt | redis-cli OK (integer) 25
Multiple runs	## runs command 5 times with no delay in between redis-cli -r 5 incr foo ## same command but with 1 second interval redis-cli -r 5 -i 1 incr foo ## runs with 100 millisecond interval redis-cli -r 100 -i 0.1 incr foo ## runs forever redis-cli -r -1 incr foo
Running LUA scripts	redis-cli --eval /tmp/script.lua foo , bar
Startup/Shutdown	## performs quit and save operation (similar to systemctl stop) redis-cli shutdown

Interactive Mode

----------------

- REPL (Read Eval Print Loop)

- Advance capabilities:

  * simulate slave and receive streams from master

  * check latency of redis server

  * check statistics

Connection	## simple connection check ping ## connecting to different instance connect node3 6379 ## selects DB number 2 select 2
Displaying	## prints db size dbsize
Multiple Runs	## running same command 5 times 5 get foo

Special Modes of Operation

--------------------------

Stat mode

$ redis-cli --stat

------- data ------ --------------------- load -------------------- - child -

keys       mem      clients blocked requests            connections

506        1015.00K 1       0       24 (+0)             7

506        1015.00K 1       0       25 (+1)             7

506        3.40M    51      0       60461 (+60436)      57

506        3.40M    51      0       146425 (+85964)     107

507        3.40M    51      0       233844 (+87419)     157

507        3.40M    51      0       321715 (+87871)     207

508        3.40M    51      0       408642 (+86927)     257

508        3.40M    51      0       497038 (+88396)     257

Scanning big keys

$ redis-cli --bigkeys

# Scanning the entire keyspace to find biggest keys as well as

# average sizes per key type.  You can use -i 0.1 to sleep 0.1 sec

# per 100 SCAN commands (not usually needed).

[00.00%] Biggest string found so far 'key-419' with 3 bytes

[05.14%] Biggest list   found so far 'mylist' with 100004 items

[35.77%] Biggest string found so far 'counter:__rand_int__' with 6 bytes

[73.91%] Biggest hash   found so far 'myobject' with 3 fields

-------- summary -------

Sampled 506 keys in the keyspace!

Total key length in bytes is 3452 (avg len 6.82)

Biggest string found 'counter:__rand_int__' has 6 bytes

Biggest   list found 'mylist' has 100004 items

Biggest   hash found 'myobject' has 3 fields

504 strings with 1403 bytes (99.60% of keys, avg size 2.78)

1 lists with 100004 items (00.20% of keys, avg size 100004.00)

0 sets with 0 members (00.00% of keys, avg size 0.00)

1 hashs with 3 fields (00.20% of keys, avg size 3.00)

0 zsets with 0 members (00.00% of keys, avg size 0.00)

Getting list of keys

redis-cli --scan | head -10

redis-cli --scan --pattern '*-11*'

redis-cli --scan --pattern 'user:*' | wc -l

PUB/SUB mode

$ redis-cli psubscribe '*'
Reading messages... (press Ctrl-C to quit)
1) "psubscribe"
2) "*"
3) (integer) 1

Monitor mode

$ redis-cli monitor
OK
1460100081.165665 [0 127.0.0.1:51706] "set" "foo" "bar"
1460100083.053365 [0 127.0.0.1:51707] "get" "foo"

Checking latency

$ redis-cli --latency
min: 0, max: 1, avg: 0.19 (427 samples)

$ redis-cli --latency-history
min: 0, max: 1, avg: 0.14 (1314 samples) -- 15.01 seconds range
min: 0, max: 1, avg: 0.18 (1299 samples) -- 15.00 seconds range
min: 0, max: 1, avg: 0.20 (113 samples)^C

Checking latency of the system running redis instance

$ ./redis-cli --intrinsic-latency 5
Max latency so far: 1 microseconds.
Max latency so far: 7 microseconds.
Max latency so far: 9 microseconds.
Max latency so far: 11 microseconds.
Max latency so far: 13 microseconds.
Max latency so far: 15 microseconds.
Max latency so far: 34 microseconds.
Max latency so far: 82 microseconds.
Max latency so far: 586 microseconds.
Max latency so far: 739 microseconds.

Backing up redis instance

$ redis-cli --rdb /tmp/dump.rdb
SYNC sent to master, writing 13256 bytes to '/tmp/dump.rdb'
Transfer finished with success.

Slave mode

$ redis-cli --slave
SYNC with master, discarding 13256 bytes of bulk transfer...
SYNC done. Logging commands from master.
"PING"
"SELECT","0"
"set","foo","bar"
"PING"
"incr","mycounter"