如何在 Varnish 3.0 上正确配置 Grace答案

【问题标题】：How to properly configure grace on Varnish 3.0如何在 Varnish 3.0 上正确配置 Grace
【发布时间】：2017-05-06 06:38:13
【问题描述】：

我正在尝试将 Varnish 配置为将第 3 方页面（由不受我控制的服务代理）缓存 1 分钟。不幸的是，这项服务有时可能会关闭，这会将麻烦转移到我的网站；为了防止这种情况，我还想在服务不可用时从本地缓存中提供服务。

我遵循了来自 grace 和 saint mode 的提示。

按照我的 VCL 文件中的一些 sn-ps。

后端配置：

backend external {
    .host = "external.acme.com";
    .port = "80";
    .probe = {
       .url = "/page";
       .interval = 5s;
       .timeout = 5s;
       .window = 1;
       .threshold = 1;
    }
}

vcl_recv：

sub vcl_recv {
    set req.backend = my_backend;

    ...

    # redirect onto 3rd part service
    if (req.url ~ "www.acme.com:80/page$") {
       set req.url = regsub(req.url, "(.*)", "http://external.acme.com/page");
       set req.backend = external;
    }

    if (!req.backend.healthy) {
        set req.grace = 2h;
    } else {
        set req.grace = 10s;
    }
    ...

vcl_fetch：

sub vcl_fetch {

    if (beresp.status == 503) {
        set beresp.saintmode = 5s;
        #set beresp.ttl = 1h;
        return (restart);
    }
    set beresp.grace = 2h;
    set beresp.ttl = 2h;

    if (req.http.host == "external.acme.com") {
        set beresp.http.X-Varnish-Action = "Caching external.acme.com";
        set beresp.ttl = 1m;
        return(deliver);
    }

我正在使用 iptables 测试远程服务的关闭，并且配置正在运行：

远程页面代理正常
3rp派对页面的健康轮询正常

我唯一的问题是：当我关闭远程服务时，第 3 方页面由缓存服务不超过一分钟（vcl_fetch 中配置的 TTL），这是远程页面时的一个很好的 TTL可用...但我想继续提供更长时间（2 小时）。

这似乎与我在那里读到的相反：http://book.varnish-software.com/3.0/Saving_a_request.html#req-grace-and-beresp-grace

我的怀疑是我没有进入宽限模式，但我在文档中发现的唯一原因是未配置 health check，但如果我查看 varnishlog 我看到运行状况检查正常运行（“仍然健康", "生病了", ...)

我错过了什么？有办法得到我需要的东西吗？

varnishlog 跟踪

一切顺利（远程服务器已启动并运行）时的此日志：

    0 Backend_health - external Still healthy 4--X-RH 1 1 1 0.010659 0.010557 HTTP/1.1 200 OK
   12 BackendClose - external
   12 BackendOpen  b external ...
   12 TxRequest    b GET
   12 TxURL        b ...
   12 TxProtocol   b HTTP/1.1
   12 TxHeader     b Cache-Control: max-age=0
   12 TxHeader     b Upgrade-Insecure-Requests: 1
   12 TxHeader     b User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36
   12 TxHeader     b Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
   12 TxHeader     b Accept-Encoding: gzip, deflate, sdch, br
   12 TxHeader     b Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4,de;q=0.2
   12 TxHeader     b Cookie:...
   12 TxHeader     b If-None-Match: "6338e-4c0f-54429328f4d3d"
   12 TxHeader     b If-Modified-Since: Wed, 21 Dec 2016 11:10:16 GMT
   12 TxHeader     b Via: 1.1 ...
   12 TxHeader     b X-Forwarded-For: ...
   12 TxHeader     b X-Forwarded-Host: ...
   12 TxHeader     b X-Forwarded-Server: ...
   12 TxHeader     b host: ...
   12 TxHeader     b X-Varnish: 1305584183
   12 RxProtocol   b HTTP/1.1
   12 RxStatus     b 304
   12 RxResponse   b Not Modified
   12 RxHeader     b Date: Thu, 22 Dec 2016 09:25:21 GMT
   12 RxHeader     b Server: Apache/2.2.22 (Debian)
   12 RxHeader     b ETag: "6338e-4c0f-54429328f4d3d"
   12 RxHeader     b Vary: Accept-Encoding
   12 Fetch_Body   b 0(none) cls 0 mklen 0
   12 Length       b 0
   12 BackendReuse b external
    3 SessionOpen  c ::1 60278 :6081
    3 ReqStart     c ::1 60278 1305584183
    3 RxRequest    c GET
    3 RxURL        c /VirtualHostBase/...
    3 RxProtocol   c HTTP/1.1
    3 RxHeader     c Host: localhost:6081
    3 RxHeader     c Cache-Control: max-age=0
    3 RxHeader     c Upgrade-Insecure-Requests: 1
    3 RxHeader     c User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36
    3 RxHeader     c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    3 RxHeader     c Accept-Encoding: gzip, deflate, sdch, br
    3 RxHeader     c Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4,de;q=0.2
    3 RxHeader     c Cookie:...
    3 RxHeader     c If-None-Match: "6338e-4c0f-54429328f4d3d"
    3 RxHeader     c If-Modified-Since: Wed, 21 Dec 2016 11:10:16 GMT
    3 RxHeader     c Via: 1.1 ...
    3 RxHeader     c X-Forwarded-For: ...
    3 RxHeader     c X-Forwarded-Host: ...
    3 RxHeader     c X-Forwarded-Server: ...
    3 RxHeader     c Connection: Keep-Alive
    3 VCL_call     c recv pass
    3 VCL_call     c hash
    3 Hash         c http://...
    3 Hash         c ...
    3 VCL_return   c hash
    3 VCL_call     c pass pass
    3 Backend      c 12 external external
    3 TTL          c 1305584183 RFC -1 -1 -1 1482398514 0 1482398721 0 0
    3 VCL_call     c fetch
    3 TTL          c 1305584183 VCL -1 7200 -1 1482398514 -0
    3 TTL          c 1305584183 VCL 7200 7200 -1 1482398514 -0
    3 TTL          c 1305584183 VCL 60 7200 -1 1482398514 -0
    3 VCL_return   c deliver
    3 ObjProtocol  c HTTP/1.1
    3 ObjResponse  c Not Modified
    3 ObjHeader    c Date: Thu, 22 Dec 2016 09:25:21 GMT
    3 ObjHeader    c Server: Apache/2.2.22 (Debian)
    3 ObjHeader    c ETag: "6338e-4c0f-54429328f4d3d"
    3 ObjHeader    c Vary: Accept-Encoding
    3 ObjHeader    c X-Varnish-Action: Caching external.acme.com
    3 VCL_call     c deliver deliver
    3 TxProtocol   c HTTP/1.1
    3 TxStatus     c 304
    3 TxResponse   c Not Modified
    3 TxHeader     c Server: Apache/2.2.22 (Debian)
    3 TxHeader     c ETag: "6338e-4c0f-54429328f4d3d"
    3 TxHeader     c Vary: Accept-Encoding
    3 TxHeader     c X-Varnish-Action: Caching external.acme.com
    3 TxHeader     c Accept-Ranges: bytes
    3 TxHeader     c Date: Thu, 22 Dec 2016 09:21:53 GMT
    3 TxHeader     c X-Varnish: 1305584183
    3 TxHeader     c Age: 0
    3 TxHeader     c Via: 1.1 varnish
    3 TxHeader     c Connection: keep-alive
    3 Length       c 0
    3 ReqEnd       c 1305584183 1482398513.625868082 1482398513.630025387 0.000263691 0.004073620 0.000083685
    3 SessionClose c EOF
    3 StatSess     c ::1 60278 0 1 1 0 1 1 290 0
    0 CLI          - Rd ping
    0 CLI          - Wr 200 19 PONG 1482398514 1.0
    0 CLI          - Rd ping
    0 CLI          - Wr 200 19 PONG 1482398517 1.0
    0 Backend_health - external Still healthy 4--X-RH 1 1 1 0.010621 0.010573 HTTP/1.1 200 OK

这是我在远程关闭时记录的内容（但由于未达到 TTL，我仍然得到缓存的内容）：

0 CLI          - Rd ping
0 CLI          - Wr 200 19 PONG 1482398997 1.0
0 Backend_health - external Went sick ------- 0 1 1 0.000000 0.010652
0 CLI          - Rd ping
0 CLI          - Wr 200 19 PONG 1482399000 1.0
3 SessionOpen  c ::1 60382 :6081
3 ReqStart     c ::1 60382 1305584190
3 RxRequest    c GET
3 RxURL        c /VirtualHostBase/https/...
3 RxProtocol   c HTTP/1.1
3 RxHeader     c Host: localhost:6081
3 RxHeader     c Pragma: no-cache
3 RxHeader     c Cache-Control: no-cache
3 RxHeader     c Upgrade-Insecure-Requests: 1
3 RxHeader     c User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36
3 RxHeader     c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
3 RxHeader     c Accept-Encoding: gzip, deflate, sdch, br
3 RxHeader     c Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4,de;q=0.2
3 RxHeader     c Cookie: ...
3 RxHeader     c Via: 1.1 ...
3 RxHeader     c X-Forwarded-For: ...
3 RxHeader     c X-Forwarded-Host: ...
3 RxHeader     c X-Forwarded-Server: ...
3 RxHeader     c Connection: Keep-Alive
3 VCL_call     c recv lookup
3 VCL_call     c hash
3 Hash         c http://...
3 Hash         c ...
3 VCL_return   c hash
3 Hit          c 1305584185
3 VCL_call     c hit deliver
3 VCL_call     c deliver deliver
3 TxProtocol   c HTTP/1.1
3 TxStatus     c 200
3 TxResponse   c OK
3 TxHeader     c Server: Apache/2.2.22 (Debian)
3 TxHeader     c Access-Control-Allow-Origin: *
3 TxHeader     c Last-Modified: Wed, 21 Dec 2016 11:10:16 GMT
3 TxHeader     c ETag: "6338e-4c0f-54429328f4d3d"
3 TxHeader     c Vary: Accept-Encoding
3 TxHeader     c Content-Encoding: gzip
3 TxHeader     c Content-Type: text/html
3 TxHeader     c X-Varnish-Action: Caching external.acme.com
3 TxHeader     c Content-Length: 4367
3 TxHeader     c Accept-Ranges: bytes
3 TxHeader     c Date: Thu, 22 Dec 2016 09:30:03 GMT
3 TxHeader     c X-Varnish: 1305584190 1305584185
3 TxHeader     c Age: 39
3 TxHeader     c Via: 1.1 varnish
3 TxHeader     c Connection: keep-alive
3 Length       c 4367
3 ReqEnd       c 1305584190 1482399003.173985004 1482399003.174190044 0.000112534 0.000087976 0.000117064
3 SessionClose c EOF
3 StatSess     c ::1 60382 0 1 1 0 0 0 441 4367
0 CLI          - Rd ping
0 CLI          - Wr 200 19 PONG 1482399003 1.0
0 CLI          - Rd ping
0 CLI          - Wr 200 19 PONG 1482399006 1.0

最后这是我在 TTL 结束后得到的错误（超过一分钟后）

    0 CLI          - Rd ping
    0 CLI          - Wr 200 19 PONG 1482399282 1.0
    0 CLI          - Rd ping
    0 CLI          - Wr 200 19 PONG 1482399285 1.0
   12 SessionOpen  c ::1 60412 :6081
   12 ReqStart     c ::1 60412 1305584191
   12 RxRequest    c GET
   12 RxURL        c /VirtualHostBase/https/...
   12 RxProtocol   c HTTP/1.1
   12 RxHeader     c Host: localhost:6081
   12 RxHeader     c Cache-Control: max-age=0
   12 RxHeader     c Upgrade-Insecure-Requests: 1
   12 RxHeader     c User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36
   12 RxHeader     c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
   12 RxHeader     c Accept-Encoding: gzip, deflate, sdch, br
   12 RxHeader     c Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4,de;q=0.2
   12 RxHeader     c Cookie: ...
   12 RxHeader     c If-None-Match: "6338e-4c0f-54429328f4d3d"
   12 RxHeader     c If-Modified-Since: Wed, 21 Dec 2016 11:10:16 GMT
   12 RxHeader     c Via: 1.1 ...
   12 RxHeader     c X-Forwarded-For: ...
   12 RxHeader     c X-Forwarded-Host: ...
   12 RxHeader     c X-Forwarded-Server: ...
   12 RxHeader     c Connection: Keep-Alive
   12 VCL_call     c recv pass
   12 VCL_call     c hash
   12 Hash         c http://...
   12 Hash         c ...
   12 VCL_return   c hash
   12 VCL_call     c pass pass
   12 FetchError   c no backend connection
   12 VCL_call     c error deliver
   12 VCL_call     c deliver deliver
   12 TxProtocol   c HTTP/1.1
   12 TxStatus     c 503
   12 TxResponse   c Service Unavailable
   12 TxHeader     c Server: Varnish
   12 TxHeader     c Content-Type: text/html; charset=utf-8
   12 TxHeader     c Retry-After: 5
   12 TxHeader     c Content-Length: 419
   12 TxHeader     c Accept-Ranges: bytes
   12 TxHeader     c Date: Thu, 22 Dec 2016 09:34:48 GMT
   12 TxHeader     c X-Varnish: 1305584191
   12 TxHeader     c Age: 0
   12 TxHeader     c Via: 1.1 varnish
   12 TxHeader     c Connection: close
   12 Length       c 419
   12 ReqEnd       c 1305584191 1482399288.281390190 1482399288.281631470 0.000269890 0.000148058 0.000093222
   12 SessionClose c error
   12 StatSess     c ::1 60412 0 1 1 0 1 0 257 419
    0 CLI          - Rd ping
    0 CLI          - Wr 200 19 PONG 1482399288 1.0
    0 Backend_health - external Still sick ------- 0 1 1 0.000000 0.010652
    0 CLI          - Rd ping
    0 CLI          - Wr 200 19 PONG 1482399291 1.0

【问题讨论】：

标签： varnish varnish-vcl

【解决方案1】：

我相信您的问题在于 vcl_fetch 中的 return (restart); 行。重新启动将强制 Varnish 从一开始就使用不同的后端处理请求，因为您没有另一个后端，这将引发错误。这就是您的对象从缓存中提供的时间不超过其 TTL 的原因。

这将是正确的流程：

TTL 有效=> 从缓存中传递；
TTL 无效=> 尝试从后端获取；
后端无响应=>使用宽限 TTL；
Grace TTL 有效=> 从过期缓存中传递；

重新启动通过不让 Varnish 进入第 4 步来改变这个流程。尝试移除它，看看奇迹发生了。

【讨论】：

感谢您的回答，以及重新启动的解释（我完全错过了）。不幸的是，删除 return(restart) 没有任何改变。我仍然得到 1 分钟的缓存内容，然后出现 503 的 Varnish 错误
如果您可以发布错误请求的日志，则更容易识别问题。尝试 varnishlog 并发布有关失败请求的所有数据，我很乐意编辑我的答案。我还建议您将 Varnish 升级到第 4 版。它在性能以及请求和获取的处理方式方面有了很大的改进。
你好@alejdg我编辑了添加varnishlog信息的问题
嘿@LucaFabbri，由于某种原因，它甚至没有寻找缓存，被调用的方法是pass，意思是“从后端获取”。恐怕我需要你发布你的整个 vcl_recv 以便我看看哪里出了问题。