lua-resty-balancer

A generic consistent hash implementation for OpenResty/Lua

Account

jojohappy

Repo

https://github.com/jojohappy/lua-resty-balancer

$ opm get jojohappy/lua-resty-balancer

Name

lua-resty-chash - A generic consistent hash implementation for OpenResty/LuaJIT

lua-resty-roundrobin - A generic roundrobin implementation for OpenResty/LuaJIT

Status

This library is still under early development and is still experimental.

Description

This Lua library can be used with balancer_by_lua*.

Synopsis

        lua_package_path "/path/to/lua-resty-chash/lib/?.lua;;";
        lua_package_cpath "/path/to/lua-resty-chash/?.so;;";
    
        init_by_lua_block {
            local resty_chash = require "resty.chash"
            local resty_roundrobin = require "resty.roundrobin"
    
            local server_list = {
                ["127.0.0.1:1985"] = 2,
                ["127.0.0.1:1986"] = 2,
                ["127.0.0.1:1987"] = 1,
            }
    
            -- XX: we can do the following steps to keep consistency with nginx chash
            local str_null = string.char(0)
    
            local servers, nodes = {}, {}
            for serv, weight in pairs(server_list) do
                -- XX: we can just use serv as id when we doesn't need keep consistency with nginx chash
                local id = string.gsub(serv, ":", str_null)
    
                servers[id] = serv
                nodes[id] = weight
            end
    
            local chash_up = resty_chash:new(nodes)
    
            package.loaded.my_chash_up = chash_up
            package.loaded.my_servers = servers
    
            local rr_up = resty_roundrobin:new(server_list)
            package.loaded.my_rr_up = rr_up
        }
    
        upstream backend_chash {
            server 0.0.0.1;
            balancer_by_lua_block {
                local b = require "ngx.balancer"
    
                local chash_up = package.loaded.my_chash_up
                local servers = package.loaded.my_servers
    
                -- we can balancer by any key here
                local id = chash_up:find(ngx.var.arg_key)
                local server = servers[id]
    
                assert(b.set_current_peer(server))
            }
        }
    
        upstream backend_rr {
            server 0.0.0.1;
            balancer_by_lua_block {
                local b = require "ngx.balancer"
    
                local rr_up = package.loaded.my_rr_up
    
                local server = rr_up:find()
    
                assert(b.set_current_peer(server))
            }
        }
    
        server {
            location /chash {
                proxy_pass http://backend_chash;
            }
    
            location /roundrobin {
                proxy_pass http://backend_rr;
            }
        }

Methods

Both resty.chash and resty.roundrobin have the same apis.

new

syntax: obj, err = class.new(nodes)

Instantiates an object of this class. The class value is returned by the call require "resty.chash".

The id should be table.concat({host, string.char(0), port}) like the nginx chash does, when we need to keep consistency with nginx chash.

The id can be any string value when we do not need to keep consistency with nginx chash.

    local nodes = {
        -- id => weight
        server1 = 10,
        server2 = 2,
    }
    
    local resty_chash = require "resty.chash"
    
    local chash = resty_chash:new(nodes)
    
    local id = chash:find("foo")
    
    ngx.say(id)

reinit

syntax: obj:reinit(nodes)

Reinit the chash obj with the new nodes.

set

syntax: obj:set(id, weight)

Set weight of the id.

delete

syntax: obj:delete(id)

Delete the id.

incr

syntax: obj:incr(id, weight?)

Increments weight for the id by the step value weight(default to 1).

decr

syntax: obj:decr(id, weight?)

Decrease weight for the id by the step value weight(default to 1).

find

syntax: id, index = obj:find(key)

Find an id by the key, same key always return the same id in the same obj.

The second return value index is the index in the chash circle of the hash value of the key.

syntax: id, new_index = obj:next(old_index)

If we have chance to retry when the first id(server) doesn't work well, then we can use obj:next to get the next id.

The new id may be the same as the old one.

Installation

First you need to run make to generate the librestychash.so. Then you need to configure the lua_package_path and lua_package_cpath directive to add the path of your lua-resty-chash source tree to ngx_lua's LUA_PATH search path, as in

        # nginx.conf
        http {
            lua_package_path "/path/to/lua-resty-chash/lib/?.lua;;";
            lua_package_cpath "/path/to/lua-resty-chash/?.so;;";
            ...
        }

Ensure that the system account running your Nginx ''worker'' proceses have enough permission to read the .lua and .so file.

Performance

There is a benchmark script t/bench.lua.

I got the result when I run make bench:

    chash new servers
    10000 times
    elasped: 0.61600017547607
    
    chash new servers2
    1000 times
    elasped: 0.77300000190735
    
    chash new servers3
    10000 times
    elasped: 0.66899991035461
    
    new in func
    10000 times
    elasped: 0.62000012397766
    
    new dynamic
    10000 times
    elasped: 0.75499987602234
    
    incr server3
    10000 times
    elasped: 0.19000029563904
    
    incr server1
    10000 times
    elasped: 0.33699989318848
    
    decr server1
    10000 times
    elasped: 0.27300024032593
    
    delete server3
    10000 times
    elasped: 0.037999868392944
    
    delete server1
    10000 times
    elasped: 0.065000057220459
    
    set server1 9
    10000 times
    elasped: 0.26600003242493
    
    set server1 8
    10000 times
    elasped: 0.32000017166138
    
    set server1 1
    10000 times
    elasped: 0.56699991226196
    
    base for find
    1000000 times
    elasped: 0.01800012588501
    
    find
    1000000 times
    elasped: 0.9469997882843

Author

Dejiang Zhu (doujiang24) <doujiang24@gmail.com>.

Copyright and License

This module is licensed under the BSD license.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.