Cacher is the code snippet organizer for pro developers

    server {
        listen       80;
        server_name  localhost;

        location ~ ^/update(/.*)$ {
            proxy_pass http://127.0.0.1:8000$1$is_args$args;
        }

        location /api/ {
            # set expire timeout, in seconds
            set $cache_timeout 3600;
            content_by_lua '
                -- TODO: support vary on specified header
                local cjson = require "cjson"

                local update_url = "/update" .. ngx.var.request_uri

                local redis = require "resty.redis"
                local red = redis:new()
                red:set_timeout(1000)

                local ok, err = red:connect("127.0.0.1", 6379)
                if not ok then
                    ngx.say("Failed to connect: ", err)
                    return
                end

                -- try get content from redis
                local key = ngx.var.request_uri
                local cache, err = red:hmget(key, "header", "body")

                if not cache then
                    -- fetch error
                    ngx.say("Failed to get ", key , err)
                    return
                end

                if cache ~= ngx.null and cache[1] ~= ngx.null then
                    -- hit cache
                    ngx.header.X_From_Page_Cache = "true"
                    local header, body = cjson.decode(cache[1]), cache[2]
                    ngx.header["Content-Type"] = header["Content-Type"]
                    ngx.say(body)
                    ngx.eof()
                else
                    -- fetch from upstream
                    ngx.log(ngx.INFO, key, " not exists")
                    local res = ngx.location.capture(update_url)

                    -- response to client & update data to cache
                    ngx.status = res.status
                    for k, v in pairs(res.header) do
                        ngx.header[k] = v
                    end
                    ngx.say(res.body)
                    ngx.eof()

                    if res.status == 200 then
                        -- NOTE: json encode&decode leads to much performance loss
                        red:hmset(key, "header", cjson.encode(res.header), "body", res.body)
                        local cache_timeout = ngx.var.cache_timeout
                        red:expire(key, cache_timeout ~= nil and cache_timeout or 60*60)
                    end
                end

                -- Puts the connection into connection pool
                -- This gets about 30% performance boost(tested by wonder)
                local ok, err = red:set_keepalive(1000*60*60, 10)
                if not ok then
                    ngx.log(ngx.EMERG, "Faied to keepalive", err)
                end
            ';
        }
    }