Jump Consisten Hash for luajit
A simple implementation of this paper.
Features
- small memory footprint and fast
- consistence is maintained through servers' updating
Installation
make
make PREFIX=/usr/local/openresty install
Usage
- you can use the basic jchash module to do consistent-hash
local jchash = require "resty.chash.jchash"
local buckets = 8
local id = jchash.hash_short_str("random key", buckets)
- or you can use the wrapping module
resty.chash.serverto consistent-hash a list of servers
local jchash_server = require "resty.chash.server"
local my_servers = {
{ "127.0.0.1", 80, 1}, -- {addr, port, weight} weight can be left out if it's 1
{ "127.0.0.2", 80 },
{ "127.0.0.3", 80 }
}
local cs, err = jchash_server.new(my_servers)
local uri = ngx.var.uri
local svr = cs:lookup(uri)
local addr = svr[1]
local port = svr[2]
-- now you can use the ngx.balancer to do some consistent LB
-- you can even update the servers list, and still maintain the consistence, eg.
local my_new_servers = {
{ "127.0.0.2", 80 },
{ "127.0.0.3", 80 },
{ "127.0.0.4", 80 }
}
cs:update_servers(my_new_servers)
svr = cs:lookup(uri) -- if the server was 127.0.0.2, then it stays the same,
-- as we only update the 127.0.0.4.
-- what's more, consistence is maintained even the number of servers changes! eg.
local my_less_servers = {
{ "127.0.0.2", 80 },
{ "127.0.0.3", 80 }
}
cs:update_servers(my_less_servers)
svr = cs:lookup(uri) -- if the server was 127.0.0.2, then it stays the same,
-- if the server was 127.0.0.4, then it has 50% chance to be
-- 127.0.0.2 or 127.0.0.3
cs:update_servers(my_new_servers)
svr = cs:lookup(uri) -- if the server was 127.0.0.2, then it has 66% chance to stay the same
Todo
weight for the servers list[done]Test::Nginx[done]
Test
make test