php 错误 503 后端提取失败
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Error 503 Backend fetch failed
提问by WebDeveloper
I have this error in my site
我的网站有这个错误
Error 503 Backend fetch failed
Backend fetch failed
Guru Meditation:
XID: 526707
Varnish cache server
错误 503 后端提取失败
后端提取失败
上师冥想：
编号：526707
优化缓存服务器
Anyone know what may be the cause or how to find out what happens?
任何人都知道可能是什么原因或如何找出发生了什么？
回答by moebin
There's a common reason that varnish returns 503 that is not explained on the varnish error list. I have learnt this from experience.
varnish 返回 503 的一个常见原因在 varnish 错误列表中没有解释。我从经验中学到了这一点。
If your web server is returning 500 error or similar then varnish simply says Error 503 Backend fetch failed.
如果您的 Web 服务器返回 500 错误或类似错误，那么 varnish 只会说 Error 503 Backend fetch failed。
what you need to do is to always try to fetch without varnish to see if the error is in varnish or the web server. For example if you have a different hostname for the webserver, load that and find the error, if you fix that, then restart varnish and that solves it most of the time.
您需要做的是始终尝试在不使用清漆的情况下进行获取，以查看错误是在清漆中还是在 Web 服务器中。例如，如果您的网络服务器有一个不同的主机名，请加载它并找到错误，如果您修复它，然后重新启动 varnish 并在大多数情况下解决它。
回答by crico_aven
That means that Varnish has been properly configured to accept incoming connections, but is not yet available to serve your backend. This error is common when varnish receives a request but your backend is still restarting/releasing.
这意味着 Varnish 已正确配置为接受传入连接，但尚无法为您的后端提供服务。当 varnish 收到请求但您的后端仍在重新启动/释放时，此错误很常见。
回答by harri
This can be due to the length of cache tags used by Magento exceeding Varnish's default of 8192 bytes.
这可能是由于 Magento 使用的缓存标签长度超过了 Varnish 的默认值 8192 字节。
This can be solved by modifying the varnish configs:
这可以通过修改清漆配置来解决：
- CentOS 6: /etc/sysconfig/varnish
- CentOS 7: /etc/varnish/varnish.params
- Ubuntu: /etc/default/varnish
- CentOS 6：/etc/sysconfig/varnish
- CentOS 7：/etc/varnish/varnish.params
- Ubuntu：/etc/default/varnish
Find http_resp_hdr_len. If the parameter doesn't exist, add it after thread_pool_max.
找到http_resp_hdr_len。如果该参数不存在，则将其添加到thread_pool_max之后。
Magento suggests setting http_resp_hdr_lento a value equal to the product count of your largest category multiplied by 21.
Magento 建议将http_resp_hdr_len设置为等于您最大类别的产品数量乘以 21 的值。
For example, setting the value to 65536 bytes should work if your largest category has 3,000 products:
例如，如果您最大的类别有 3,000 个产品，则将值设置为 65536 字节应该可以工作：
-p http_resp_hdr_len=65536 \
See here: http://devdocs.magento.com/guides/v2.0/config-guide/varnish/tshoot-varnish-503.html
请参阅此处：http: //devdocs.magento.com/guides/v2.0/config-guide/varnish/tshoot-varnish-503.html
