redis-lua
redis-lua copied to clipboard
nrk
A Lua client library for the redis key value storage system.
redis-lua
About
redis-lua 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
Include redis-lua 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:nrk', 10)
client:set('usr:nobody', 5)
local value = client:get('usr:nrk') -- 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:nrk:ids',v)
end
local sorted = client:sort('usr:nrk: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 redis-lua 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
- Lua 5.1 and 5.2 or LuaJIT 2.0
- LuaSocket 2.0
- Telescope (required to run the test suite)
Links
Project
Related
Authors
Daniele Alessandri
Contributors
License
The code for redis-lua is distributed under the terms of the MIT/X11 license (see LICENSE).
nrk