lua-resty-balancer

by openresty

A generic consistent hash implementation for OpenResty/Lua

222 Stars 57 Forks Last release: Not found 25 Commits 7 Releases

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Name

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

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

Table of Contents

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

        -- Note that Round Robin picks the first server randomly
        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;
    }
}

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Methods

Both

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

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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)

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reinit

syntax:

obj:reinit(nodes)

Reinit the chash obj with the new

nodes
.

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set

syntax:

obj:set(id, weight)

Set

weight
of the
id
.

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delete

syntax:

obj:delete(id)

Delete the

id
.

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incr

syntax:

obj:incr(id, weight?)

Increments weight for the

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

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decr

syntax:

obj:decr(id, weight?)

Decrease weight for the

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

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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
.

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next

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.

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Installation

First you need to run

make
to generate the librestychash.so. Then you need to configure the luapackagepath and luapackagecpath directive to add the path of your lua-resty-chash source tree to ngxlua's LUAPATH 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.

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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

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Author

Dejiang Zhu (doujiang24) [email protected].

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Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2015-2016, by Yichun Zhang (agentzh) [email protected], CloudFlare Inc.

All rights reserved.

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.

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See Also

  • the ngx_lua module: http://wiki.nginx.org/HttpLuaModule
  • the json lib for Lua and C: https://github.com/cloudflare/lua-resty-json

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