1 files changed, 135 insertions, 0 deletions
diff --git a/openresty-ext/src/assembly/resources/openresty/nginx/luaext/loadbalance/policy/consistent_hash.lua b/openresty-ext/src/assembly/resources/openresty/nginx/luaext/loadbalance/policy/consistent_hash.lua
new file mode 100644
index 0000000..b3cd46e
--- /dev/null
+++ b/openresty-ext/src/assembly/resources/openresty/nginx/luaext/loadbalance/policy/consistent_hash.lua
@@ -0,0 +1,135 @@
+--[[
+
+    Copyright (C) 2018 ZTE, Inc. and others. All rights reserved. (ZTE)
+
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
+
+            http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
+
+--]]
+
+local _M = {}
+_M._VERSION = '1.0.0'
+
+local floor      = math.floor
+local str_byte   = string.byte
+local tab_sort   = table.sort
+local tab_insert = table.insert
+
+local MOD       = 2 ^ 32
+local REPLICAS  = 20
+local LUCKY_NUM = 13
+
+
+local tbl_util  = require('lib.utils.table_util')
+local tbl_isempty = tbl_util.isempty
+local tbl_isequal = require('pl.tablex')
+local peerwatcher = require "core.peerwatcher"
+local ngx_var = ngx.var
+local hash_data = {}
+
+local function hash_string(str)
+    local key = 0
+    for i = 1, #str do
+        key = (key * 31 + str_byte(str, i)) % MOD
+    end
+    return key
+end
+
+
+local function init_consistent_hash_state(servers)
+    local weight_sum = 0
+    local weight = 1
+    for _, srv in ipairs(servers) do
+        if srv.weight  and srv.weight ~= 0 then
+            weight = srv.weight
+        end
+        weight_sum = weight_sum + weight
+    end
+
+    local circle, members = {}, 0
+    for index, srv in ipairs(servers) do
+        local key = ("%s:%s"):format(srv.ip, srv.port)
+        local base_hash = hash_string(key)
+        for c = 1, REPLICAS * weight_sum do
+            local hash = (base_hash * c * LUCKY_NUM) % MOD
+            tab_insert(circle, { hash, index })
+        end
+        
+        members = members + 1
+    end
+    tab_sort(circle, function(a, b) return a[1] < b[1] end)
+    return { circle = circle, members = members }
+end
+
+local function update_consistent_hash_state(hash_data,servers,svckey)
+    -- compare servers in ctx with servers in cache
+    -- update the hash data if changes occur
+    local serverscache = hash_data[svckey].servers
+    tab_sort(serverscache, function(a, b) return a.ip < b.ip end)
+    tab_sort(servers, function(a, b) return a.ip < b.ip end)
+    if  not tbl_isequal.deepcompare(serverscache, servers, false) then
+        local tmp_chash = init_consistent_hash_state(servers)
+        hash_data[svckey].servers =servers
+        hash_data[svckey].chash = tmp_chash
+    end
+end
+
+local function binary_search(circle, key)
+    local size = #circle
+    local st, ed, mid = 1, size
+
+    while st <= ed do
+        mid = floor((st + ed) / 2)
+        if circle[mid][1] < key then
+            st = mid + 1
+        else
+            ed = mid - 1
+        end
+    end
+
+    return st == size + 1 and 1 or st
+end
+
+
+function _M.select_backserver(servers,svckey)
+
+    if hash_data[svckey] == nil then
+        local tbl = {}
+        tbl['servers'] = {}
+        tbl['chash'] = {}
+        hash_data[svckey] = tbl
+    end
+
+    if tbl_isempty(hash_data[svckey].servers) then
+        local tmp_chash = init_consistent_hash_state(servers)
+        hash_data[svckey].servers = servers
+        hash_data[svckey].chash = tmp_chash
+    else
+        update_consistent_hash_state(hash_data,servers,svckey)
+    end
+
+    local chash = hash_data[svckey].chash
+    local circle = chash.circle
+    local hash_key = ngx_var.remote_addr
+    local st = binary_search(circle, hash_string(hash_key))
+    local size = #circle
+    local ed = st + size - 1
+    for i = st, ed do
+        local idx = circle[(i - 1) % size + 1][2]
+        if peerwatcher.is_server_ok(svckey,hash_data[svckey].servers[idx]) then
+            return hash_data[svckey].servers[idx]
+        end
+    end
+    return nil, "consistent hash: no servers available"
+end
+
+return _M