使用varnish 4代理處理jsonp接口

原文地址： http://blog.wangjunfeng.com/a...

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背景

使用varnish是一個很不錯的HTTP加速方案，挪威最大的在線報紙 Verdens Gang 使用3臺Varnish代替了原來的12臺Squid，性能比之前更好。然而varnish默認狀況下是以url進行hash，來標識緩存，因此對於jsonp這種帶有callback參數的請求，每一次callback都不同，極可能會生成大量重複數據，佔用內存空間，浪費資源。最近就遇到了這個問題，好在這個仍是有解決辦法的。

實現原理

其實jsonp很簡單，就是json數據加一個callback和一對括號就能夠了，因此只要咱們取到沒有callback的json數據，並進行緩存，再把數據用標籤包起來就能夠了。是的，就是這麼簡單，可是如何實現呢？

其實實現起來也很簡單，在varnish 4的VCL裏面其實能夠使用synthetic來組合數據，可是這個函數又只能在vcl_synth和vcl_backend_error內使用，其中vcl_synth是用來處理錯誤的，而vcl_backend_error是用來處理後端服務器錯誤，因此咱們就必須先拋出錯誤，而後讀取json數據，再進行拼接，而後返回。

這裏拼接數據時還須要用到varnish的Edge Side Includes(ESI)。

代碼示例

#
# This is an example VCL file for Varnish.
#
# It does not do anything by default, delegating control to the
# builtin VCL. The builtin VCL is called when there is no explicit
# return statement.
#
# See the VCL chapters in the Users Guide at https://www.varnish-cache.org/docs/
# and https://www.varnish-cache.org/trac/wiki/VCLExamples for more examples.

# Marker to tell the VCL compiler that this VCL has been adapted to the
# new 4.0 format.
vcl 4.0;

# Default backend definition. Set this to point to your content server.

# 後端服務器
backend default {
    .host = "127.0.0.1";
    .port = "8000";
    .connect_timeout = 8s;
    .first_byte_timeout = 8s;
    .between_bytes_timeout = 5s;
}

# varnish服務器
backend jsonp_template_backend {
  .host = "127.0.0.1";
  .port = "80";
}

sub vcl_recv {
    # 當地址是/JSONP-ESI-TEMPLATE時，則拋出760錯誤
    if (req.url == "/JSONP-ESI-TEMPLATE") {
        return (synth(760, "Json"));
    }
}

sub vcl_recv {
    # Happens before we check if we have this in cache already.
    #
    # Typically you clean up the request here, removing cookies you don't need,
    # rewriting the request, etc.
    if (req.method != "GET") {
        return (pass);
    }
    if (req.url ~ "callback=") {
        # 保存callback參數，後續拼裝數據時會使用到
        set req.http.X-Callback = regsub(
            req.url, ".*[\?&]callback=([\.A-Za-z0-9_]+).*", "\1"
        );
        # 去除callback和_參數
        set req.http.X-ESI-Url = regsub(req.url, "&?callback=[\.A-Za-z0-9_]+", "");
        set req.http.X-ESI-Url = regsub(req.http.X-ESI-Url, "&?_=[\.A-Za-z0-9_]+", "");
        set req.http.X-ESI-Url = regsub(req.http.X-ESI-Url, "\?$", "");
        set req.http.X-ESI-Url = regsub(req.http.X-ESI-Url, "\?&", "?");
        # 設置後端請求地址
        set req.url = "/JSONP-ESI-TEMPLATE";
        # 設置請求後端服務器
        set req.backend_hint = jsonp_template_backend;
        return (pass);
    }
    return (hash);
}

sub vcl_backend_response {
    # 若是後端請求包含有X-ESI則啓用X-ESI
    if (beresp.http.X-ESI) {
        unset beresp.http.X-ESI;
        set beresp.do_esi = true;
    }
}

sub vcl_backend_response {
    # X-JSONP-Server means we need to clean up the response a bit
    if (beresp.http.X-JSONP-Server) {
        unset beresp.http.X-JSONP-Server;
        set beresp.http.Server = "JSONP-Server";
    }
}

sub vcl_synth {
    # 處理760錯誤，這裏設置相關參數，後續請求後端要用到
    if (resp.status == 760) {
        set resp.http.X-ESI = "1";
        set resp.http.X-JSONP-Server = "1";
        
        # 設置狀態碼爲200
        set resp.status = 200;
        
        # 數據拼接，拼接後直接返回
        synthetic({"<esi:include />"} + {"/**/"} + req.http.X-Callback + {"(<esi:include src="} +  req.http.X-ESI-Url + {" />)"});
        return(deliver);
    }
}

sub vcl_backend_response {
    # Happens after we have read the response headers from the backend.
    #
    # Here you clean the response headers, removing silly Set-Cookie headers
    # and other mistakes your backend does.
    unset beresp.http.set-cookie;
    if (beresp.ttl <= 0s) {
        set beresp.ttl = 120s;
    }
    set beresp.do_gzip = true;
    return (deliver);
}

sub vcl_deliver {
    # Happens when we have all the pieces we need, and are about to send the
    # response to the client.
    #
    # You can do accounting or modifying the final object here.
}

注意

這裏的代碼是varnish 4.*版本的代碼示例，若是使用了其餘版本的varnish配置可能有所不一樣。若是使用較低版本，varnish 4裏面有些語法已經變動。使用時可能須要修改一下。

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原文地址： http://blog.wangjunfeng.com/a...