這裏的路由指的是在web開發中，訪問路徑以及具體實現內容的映射。比如，/a映射到某個具體的頁面，這個就稱之爲一個路由。而動態路由，顧名思義就是動態添加這種路由映射關係。
在nginx中，通過rewrite和proxy_pass來實現路由映射或者說反向代理，但是這種關係按照傳統的配置必須寫死在配置文件中，然後通過快速"無縫"重啓nginx。雖說是無縫，但是其繁瑣的配置和枯燥的重啓操作還是無法避免。
最近，在github上看到個項目ceryx，是nginx結合lua進行動態路由的映射的，也就是上面所說的映射關係，用lua來管理，雖然是比較簡單的實現，但是可以分析學習下。該項目通過用redis的<source,target>結構來保存這種映射關係，這樣在nginx中可以快速獲得這種關係，以便做出處理，同時，採用HTTP的形式暴露對redis這種路由關係進行管理的接口。
from ceryx.db import RedisRouter
resource_fields = {
'source': fields.String,
'target': fields.String,
}
parser = reqparse.RequestParser()
parser.add_argument(
'source', type=str, required=True, help='Source is required'
)
parser.add_argument(
'target', type=str, required=True, help='Target is required'
)
router = RedisRouter.from_config()
def lookup_or_abort(source):
"""
Returns the target for the given source, or aborts raising a 404
"""
try:
return {'source': source, 'target': router.lookup(source)}
except RedisRouter.LookupNotFound:
abort(
404, message='Route with source {} doesn\'t exist'.format(source)
)
class Route(Resource):
"""
Resource describing a single Route. Supports GET, DELETE and PUT. The
format is the following:
```
{
"source": "[source]",
"target": "[target]"
}
```
"""
@marshal_with(resource_fields)
def get(self, source):
"""
Fetches the route with the given source
"""
route = lookup_or_abort(source)
return route
@marshal_with(resource_fields)
def delete(self, source):
"""
Deletes the route with the given source
"""
route = lookup_or_abort(source)
router.delete(source)
return route, 204
@marshal_with(resource_fields)
def put(self, source):
"""
Creates or updates the route with the given source, pointing to the
given target
"""
args = parser.parse_args()
router.insert(args['source'], args['target'])
return args, 201上述的代碼，是進行路由管理的http api，當然，這個不是我們分析的重點。先來看一下，在這個項目裏面，對nginx的配置是怎樣的
upstream fallback {
server www.something.com;
}
server {
listen 80;
default_type text/html;
location / {
set $container_url "fallback";
resolver 8.8.8.8;
# Lua files
access_by_lua_file lualib/router.lua;//切入點
# Proxy configuration
proxy_set_header Host $http_host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_redirect ~^(http://[^:]+):\d+(/.+)$ $2;
proxy_redirect / /;
# Upgrade headers
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_pass http://$container_url$request_uri;
}
...
}local container_url = ngx.var.container_url//拿到配置文件中的container_url
local host = ngx.var.host //拿到請求的時候的host，比如我們請求http://www.xxx.com/a.html 那這裏的host就是www.xxx.com
-- Check if key exists in local cache
local cache = ngx.shared.ceryx
local res, flags = cache:get(host) //直接在nginx cache中拿host對應的路由映射，如果存在則直接返回結果
if res then
ngx.var.container_url = res
return
end
local redis = require "resty.redis" // redis的連接代碼 每次都會連接redis，
local red = redis:new()<span style="white-space:pre"> </span>//<span style="font-family: Arial, Helvetica, sans-serif;">這個操作比較相對比較耗時 所以接下來的操作纔會在本地cache中存對應的關係</span>
red:set_timeout(100) -- 100 ms
local redis_host = os.getenv("CERYX_REDIS_HOST")
if not redis_host then redis_host = "127.0.0.1" end
local redis_port = os.getenv("CERYX_REDIS_PORT")
if not redis_port then redis_port = 6379 end
local res, err = red:connect(redis_host, redis_port)
-- Return if could not connect to Redis
if not res then
return
end
-- Construct Redis key
local prefix = os.getenv("CERYX_REDIS_PREFIX")
if not prefix then prefix = "ceryx" end
local key = prefix .. ":routes:" .. host
-- Try to get target for host
res, err = red:get(key)
if not res or res == ngx.null then
-- Construct Redis key for $wildcard
key = prefix .. ":routes:$wildcard"
res, err = red:get(key)
if not res or res == ngx.null then
return
end
ngx.var.container_url = res
return
end
-- Save found key to local cache for 5 seconds
cache:set(host, res, 5) // 在redis取出的映射關係存到redis的cache中避免下次繼續連redis操作
ngx.var.container_url = res