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luaredis

About

luaredis is a pure Lua client library for the Redis advanced key-value database.

Main features

  • Support for Redis >= 1.2
  • Command pipelining
  • Redis transactions (MULTI/EXEC) with CAS
  • User-definable commands
  • UNIX domain sockets (when available in LuaSocket)

Compatibility

This library is tested and works with Lua 5.1, Lua 5.2 (using a compatible version of LuaSocket) and LuaJit 2.0.

Examples of usage

Installation

  • The redis.lua file should be dropped into an existing project or install via luarocks
luarocks install luaredis

Include luaredis in your script

Just require the redis module assigning it to a variable:

local redis = require 'redis'

Previous versions of the library defined a global Redis alias as soon as the module was imported by the user. This global alias is still defined but it is considered deprecated and it will be removed in the next major version.

Connect to a redis-server instance and send a PING command

local redis = require 'redis'
local client = redis.connect('127.0.0.1', 6379)
local response = client:ping()           -- true

It is also possible to connect to a local redis instance using UNIX domain sockets if LuaSocket has been compiled with them enabled (unfortunately it is not the default):

local redis = require 'redis'
local client = redis.connect('unix:///tmp/redis.sock')

Set keys and get their values

client:set('usr:git', 10)
client:set('usr:nobody', 5)
local value = client:get('usr:git')      -- 10

Sort list values by using various parameters supported by the server

for _,v in ipairs({ 10,3,2,6,1,4,23 }) do
    client:rpush('usr:git:ids',v)
end

local sorted = client:sort('usr:git:ids', {
     sort = 'asc', alpha = true, limit = { 1, 5 }
})      -- {1=10,2=2,3=23,4=3,5=4}

Pipeline commands

local replies = client:pipeline(function(p)
    p:incrby('counter', 10)
    p:incrby('counter', 30)
    p:get('counter')
end)

Variadic commands

Some commands such as RPUSH, SADD, SINTER and others have been improved in Redis 2.4 to accept a list of values or keys depending on the nature of the command. Sometimes it can be useful to pass these arguments as a list in a table, but since luaredis does not currently do anything to handle such a case you can use unpack() albeit with a limitation on the maximum number of items which is defined in Lua by LUAI_MAXCSTACK (the default on Lua 5.1 is set to 8000, see luaconf.h):

local values = { 'value1', 'value2', 'value3' }
client:rpush('list', unpack(values))

-- the previous line has the same effect of the following one:
client:rpush('list', 'value1', 'value2', 'value3')

Leverage Redis MULTI / EXEC transaction (Redis > 2.0)

local replies = client:transaction(function(t)
    t:incrby('counter', 10)
    t:incrby('counter', 30)
    t:get('counter')
end)

Leverage WATCH / MULTI / EXEC for check-and-set (CAS) operations (Redis > 2.2)

local options = { watch = "key_to_watch", cas = true, retry = 2 }
local replies = client:transaction(options, function(t)
    local val = t:get("key_to_watch")
    t:multi()
    t:set("akey", val)
    t:set("anotherkey", val)
end)

Get useful information from the server

for k,v in pairs(client:info()) do
    print(k .. ' => ' .. tostring(v))
end
--[[
redis_git_dirty => 0
redis_git_sha1 => aaed0894
process_id => 23115
vm_enabled => 0
hash_max_zipmap_entries => 64
expired_keys => 9
changes_since_last_save => 2
role => master
last_save_time => 1283621624
used_memory => 537204
bgsave_in_progress => 0
redis_version => 2.0.0
multiplexing_api => epoll
total_connections_received => 314
db0 => {keys=3,expires=0}
pubsub_patterns => 0
used_memory_human => 524.61K
pubsub_channels => 0
uptime_in_seconds => 1033
connected_slaves => 0
connected_clients => 1
bgrewriteaof_in_progress => 0
blocked_clients => 0
arch_bits => 32
total_commands_processed => 3982
hash_max_zipmap_value => 512
db15 => {keys=1,expires=0}
uptime_in_days => 0
]]

Dependencies

Links

Project

Related

Editor

Minh Minh

Origin Authors

Daniele Alessandri

License

MIT (see LICENSE)