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Added Remote Cache Status class to obtain the first healthy redis nod…
…e from an upstream (#7) [#7] Added Remote Cache Status class to obtain the first healthy redis node from an upstream
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,177 @@ | ||
| --[[ | ||
| Copyright 2016 Adobe Systems Incorporated. All rights reserved. | ||
| This file is licensed to you 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 RESPRESENTATIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. | ||
| ]] | ||
| -- | ||
| -- Module for selecting a healthy server from an upstream. | ||
| -- It's best to be used with health-checks so that a peer is maked UP or DOWN | ||
| -- User: nramaswa | ||
| -- Date: 4/17/14 | ||
| -- Time: 7:38 PM | ||
|
|
||
| local _M = {} | ||
| local DEFAULT_SHARED_DICT = "cachedkeys" | ||
|
|
||
| function _M:new(o) | ||
| o = o or {} | ||
| setmetatable(o, self) | ||
| self.__index = self | ||
| if ( o ~= nil ) then | ||
| self.shared_dict = o.shared_dict or DEFAULT_SHARED_DICT | ||
| end | ||
| return o | ||
| end | ||
|
|
||
| --- Reused from the "resty.upstream.healthcheck" module to get the | ||
| -- status of the upstream servers | ||
| local function gen_peers_status_info(peers, bits, idx) | ||
| local npeers = #peers | ||
| for i = 1, npeers do | ||
| local peer = peers[i] | ||
| bits[idx] = peer.name | ||
| if peer.down then | ||
| bits[idx + 1] = " DOWN\n" | ||
| else | ||
| bits[idx + 1] = " up\n" | ||
| end | ||
| idx = idx + 2 | ||
| end | ||
| return idx | ||
| end | ||
|
|
||
| --- Returns the results of the health checks for the provided upstream_name | ||
| -- as found in the "resty.upstream.healthcheck" module. | ||
| -- @param upstream_name | ||
| -- | ||
| local function get_health_check_for_upstream(upstream_name) | ||
| local ok, upstream = pcall(require, "ngx.upstream") | ||
| if not ok then | ||
| error("ngx_upstream_lua module required") | ||
| end | ||
|
|
||
| local get_primary_peers = upstream.get_primary_peers | ||
| local get_backup_peers = upstream.get_backup_peers | ||
|
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||
| local ok, new_tab = pcall(require, "table.new") | ||
| if not ok or type(new_tab) ~= "function" then | ||
| new_tab = function (narr, nrec) return {} end | ||
| end | ||
|
|
||
| local n = 1 | ||
| local bits = new_tab(n * 20, 0) | ||
| local idx = 1 | ||
|
|
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| local peers, err = get_primary_peers(upstream_name) | ||
| if not peers then | ||
| return "failed to get primary peers in upstream " .. upstream_name .. ": " | ||
| .. err | ||
| end | ||
|
|
||
| idx = gen_peers_status_info(peers, bits, idx) | ||
|
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| peers, err = get_backup_peers(upstream_name) | ||
| if not peers then | ||
| return "failed to get backup peers in upstream " .. upstream_name .. ": " | ||
| .. err | ||
| end | ||
|
|
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| idx = gen_peers_status_info(peers, bits, idx) | ||
|
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| return bits | ||
| end | ||
|
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| --- Returns a cached healthy upstream. | ||
| -- @param dict_name shared dict name | ||
| -- @param upstream_name the name of the upstream as defined in the config | ||
| -- | ||
| local function get_healthy_upstream_from_cache(dict_name, upstream_name) | ||
| local dict = ngx.shared[dict_name] | ||
| local healthy_upstream | ||
| local health_upstream_key = "healthy_upstream:" .. tostring(upstream_name) | ||
| if (nil ~= dict) then | ||
| healthy_upstream = dict:get(health_upstream_key) | ||
| end | ||
| return healthy_upstream | ||
| end | ||
|
|
||
| local function update_healthy_upstream_in_cache(dict_name, upstream_name, healthy_upstream) | ||
| local dict = ngx.shared[dict_name]; | ||
| if (nil ~= dict) then | ||
| ngx.log(ngx.DEBUG, "Saving a healthy upstream:", healthy_upstream, " in cache:", dict_name, " for upstream:", upstream_name) | ||
| local exp_time_in_seconds = 5 | ||
| local health_upstream_key = "healthy_upstream:" .. tostring(upstream_name) | ||
| dict:set(health_upstream_key, healthy_upstream, exp_time_in_seconds) | ||
| return | ||
| end | ||
|
|
||
| ngx.log(ngx.WARN, "Dictionary ", dict_name, " doesn't seem to be set. Did you define one ? ") | ||
| end | ||
|
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| --- Returns the host and port from an upstream like host:port | ||
| -- @param upstream_host | ||
| -- | ||
| local function get_host_and_port_in_upstream(upstream_host) | ||
| local p = {} | ||
| p.host = upstream_host | ||
|
|
||
| local idx = string.find(upstream_host, ":", 1, true) | ||
| if idx then | ||
| p.host = string.sub(upstream_host, 1, idx - 1) | ||
| p.port = tonumber(string.sub(upstream_host, idx + 1)) | ||
| end | ||
| return p.host, p.port | ||
| end | ||
|
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|
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| function _M:getStatus(upstream_name) | ||
| return get_health_check_for_upstream(upstream_name) | ||
| end | ||
|
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| --- Returns the first healthy server found in the upstream_name | ||
| -- Returns 3 values: <upstreamName , host, port > | ||
| -- The difference between upstream and <host,port> is that the upstream may be just a string containing host:port | ||
| -- @param upstream_name | ||
| -- | ||
| function _M:getHealthyServer(upstream_name) | ||
|
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| -- get the host and port from the local cache first | ||
| local healthy_host = get_healthy_upstream_from_cache(self.shared_dict, upstream_name) | ||
| if ( nil ~= healthy_host) then | ||
| local host, port = get_host_and_port_in_upstream(healthy_host) | ||
| return healthy_host, host, port | ||
| end | ||
|
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||
| -- if the host is not in the local cache get it from the upstream configuration | ||
| ngx.log(ngx.DEBUG, "Looking up for a healthy peer in upstream:", upstream_name) | ||
| local upstream_health_result = get_health_check_for_upstream(upstream_name) | ||
|
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| if(upstream_health_result == nil) then | ||
| ngx.log(ngx.ERR, "\n No upstream results!") | ||
| return nil | ||
| end | ||
|
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| for key,value in ipairs(upstream_health_result) do | ||
| -- return the first peer found to be up. | ||
| -- TODO: save all the peers that are up and return them using round-robin alg | ||
| if(value == " up\n") then | ||
| healthy_host = upstream_health_result[key-1] | ||
| update_healthy_upstream_in_cache(self.shared_dict, upstream_name, healthy_host) | ||
| local host, port = get_host_and_port_in_upstream(healthy_host) | ||
| return healthy_host, host, port | ||
| end | ||
| if(value == " DOWN\n" and upstream_health_result[key-1] ~= nil ) then | ||
| ngx.log(ngx.WARN, "Peer ", tostring(upstream_health_result[key-1]), " is down! Checking for backup peers.") | ||
| end | ||
| end | ||
|
|
||
| ngx.log(ngx.ERR, "All peers are down!") | ||
| return nil -- No peers are up | ||
| end | ||
|
|
||
| return _M |
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