![Apache 运行时出现“FetchError 没有后端连接”错误](https://linux22.com/image/771732/Apache%20%E8%BF%90%E8%A1%8C%E6%97%B6%E5%87%BA%E7%8E%B0%E2%80%9CFetchError%20%E6%B2%A1%E6%9C%89%E5%90%8E%E7%AB%AF%E8%BF%9E%E6%8E%A5%E2%80%9D%E9%94%99%E8%AF%AF.png)
[centos@ip-172-35-25-65 ~]$ varnishlog
0 CLI - Rd ping
0 CLI - Wr 200 19 PONG 1635280998 1.0
0 CLI - Rd ping
0 CLI - Wr 200 19 PONG 1635281001 1.0
10 SessionOpen c 127.0.0.2 55870 127.0.0.2:80
10 ReqStart c 127.0.0.2 55870 894208400
10 RxRequest c GET
10 RxURL c /
10 RxProtocol c HTTP/1.0
10 RxHeader c X-Real-IP: 198.95.75.75
10 RxHeader c X-Forwarded-For: 198.95.75.75
10 RxHeader c X-Forwarded-Proto: https
10 RxHeader c X-Forwarded-Port: 80
10 RxHeader c Host: staging03.cherry.com
10 RxHeader c Connection: close
10 RxHeader c Cache-Control: max-age=0
10 RxHeader c Authorization: Basic aGc6am9objEyMw==
10 RxHeader c Upgrade-Insecure-Requests: 1
10 RxHeader c User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.54 Safari/537.36
10 RxHeader c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
10 RxHeader c Accept-Encoding: gzip, deflate
10 RxHeader c Accept-Language: en-US,en;q=0.9,fr;q=0.8
10 RxHeader c Cookie: ajs_anonymous_id=%22424f4cd9-cbbc-4ead-83b1-273cb21cf453%22; _fbp=fb.1.1630002144579.2012566540; __qca=P0-1416512434-1630002144589; _edwvts=708154457303700204; _gid=GA1.2.1572498662.1635275261; ajs_user_id=%224543534%40mimpi99.com%22; _gcl_au=1.1.
10 VCL_call c recv pass
10 VCL_call c hash
10 Hash c /
10 Hash c staging03.cherry.com
10 Hash c 80
10 Hash c ajs_anonymous_id=%22424f4cd9-cbbc-4ead-83b1-273cb21cf453%22; _fbp=fb.1.1630002144579.2012566540; __qca=P0-1416512434-1630002144589; _edwvts=708154457303700204; _gid=GA1.2.1572498662.1635275261; ajs_user_id=%224543534%40mimpi99.com%22; _gcl_au=1.1.1880042
10 VCL_return c hash
10 VCL_call c pass pass
10 FetchError c no backend connection
10 VCL_call c error deliver
10 VCL_call c deliver deliver
10 TxProtocol c HTTP/1.1
10 TxStatus c 503
10 TxResponse c Service Unavailable
10 TxHeader c Server: Varnish
10 TxHeader c Content-Type: text/html; charset=utf-8
10 TxHeader c Retry-After: 5
10 TxHeader c Content-Length: 392
10 TxHeader c Accept-Ranges: bytes
10 TxHeader c Date: Tue, 26 Oct 2021 20:43:23 GMT
10 TxHeader c X-Varnish: 894208400
10 TxHeader c Via: 1.1 varnish
10 TxHeader c Connection: close
10 TxHeader c X-Age: 0
10 TxHeader c X-Cache: MISS
10 Length c 392
10 ReqEnd c 894208400 1635281003.852778196 1635281003.852984428 0.000073195 0.000165701 0.000040531
10 SessionClose c error
10 StatSess c 127.0.0.2 55870 0 1 1 0 1 0 273 392
0 CLI - Rd ping
0 CLI - Wr 200 19 PONG 1635281004 1.0
0 CLI - Rd ping
0 CLI - Wr 200 19 PONG 1635281007 1.0
0 CLI - Rd ping
0 CLI - Wr 200 19 PONG 1635281010 1.0
0 CLI - Rd ping
0 CLI - Wr 200 19 PONG 1635281013 1.0
我尝试记录从客户端收到消息时发生的事情:
Error 503 Service Unavailable
Service Unavailable
Guru Meditation:
XID: 894208400
现在,我认为这是因为 Apache 没有运行,因为当我关闭 varnish 时,我收到来自 nginx 的 502 网关错误。无论如何,我阅读了错误日志:
[Tue Oct 26 14:53:47 2021] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Tue Oct 26 14:53:47 2021] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Tue Oct 26 14:53:47 2021] [notice] Digest: generating secret for digest authentication ...
[Tue Oct 26 14:53:47 2021] [notice] Digest: done
[Tue Oct 26 14:53:47 2021] [notice] FastCGI: process manager initialized (pid 23090)
[Tue Oct 26 14:53:47 2021] [notice] Apache/2.2.15 (Unix) DAV/2 mod_fastcgi/2.4.6 configured -- resuming normal operations
[Tue Oct 26 14:53:52 2021] [error] [client 127.0.0.1] Directory index forbidden by Options directive: /var/www/html/
[Tue Oct 26 14:53:52 2021] [error] [client 127.0.0.1] File does not exist: /var/www/html/favicon.ico, referer: http://staging03.hgreg.com/
[Tue Oct 26 15:01:21 2021] [error] [client 127.0.0.1] Directory index forbidden by Options directive: /var/www/html/
[Tue Oct 26 15:01:42 2021] [notice] caught SIGTERM, shutting down
[Tue Oct 26 15:01:42 2021] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0
[Tue Oct 26 15:01:42 2021] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Tue Oct 26 15:01:42 2021] [notice] Digest: generating secret for digest authentication ...
[Tue Oct 26 15:01:42 2021] [notice] Digest: done
[Tue Oct 26 15:01:42 2021] [notice] FastCGI: process manager initialized (pid 23299)
[Tue Oct 26 15:01:42 2021] [notice] Apache/2.2.15 (Unix) DAV/2 mod_fastcgi/2.4.6 configured -- resuming normal operations
[Tue Oct 26 15:11:56 2021] [notice] caught SIGTERM, shutting down
我看到了 SIGTERM,正在关闭,所以我认为也许我应该重新启动 Apache,然后我就这样做了,但是我得到了同样的错误,并且 error_log 中没有新的日志。
[centos@ip-172-35-25-65 ~]$ sudo service httpd restart
Stopping httpd: [ OK ]
Starting httpd: [ OK ]
[centos@ip-172-35-25-65 ~]$ date
Tue Oct 26 17:12:32 EDT 2021
[centos@ip-172-35-25-65 ~]$
现在,我运行了一个 puppet 配置,但它没有完全运行,但我有相同的文件。所以我想知道问题可能是什么。由于所有带有 conf 的文件都已加载,因此加载的 Apache 配置文件之一如下所示:
<VirtualHost *>
ServerName preprod.staging03.cherry.com
ServerAlias betacherry.staging03.cherry.com staging03.cherry.com
DocumentRoot /home/staging03/version/preprod.staging03.cherry.com
ServerAdmin [email protected]
SetEnv environment preprod
SetEnv project staging03
UseCanonicalName Off
#CustomLog /var/log/httpd/preprod.staging03.cherry.com_log combined
#CustomLog /var/log/httpd/preprod.staging03.cherry.com-bytes_log "%{%s}t %I .\n%{%s}t %O ."
## User cherry # Needed for Cpanel::ApacheConf
UserDir disabled
UserDir enabled staging03
#<IfModule mod_suphp.c>
# suPHP_UserGroup staging03 staging03
#</IfModule>
SuexecUserGroup staging03 staging03
<directory "/home/staging03/version">
AddHandler php5-fcgi .php
Action php5-fcgi /php5-fcgi-staging03
AllowOverride All
AuthType Basic
AuthName "staging03-preprod"
AuthUserFile "/etc/httpd/conf.d/htpasswd.staging03"
require valid-user
satisfy any
deny from all
Order deny,allow
SetEnvIf X-Hg-Internal-IP 1 HgInternalIP=1
Allow from env=HgInternalIP
SetEnvIf User-Agent "Amazon CloudFront" AmazonCloudFront
Allow from env=AmazonCloudFront
SetEnvIf User-Agent "^(.*)Lighthouse(.*)$" Lighthouse=1
Allow from env=Lighthouse
</directory>
<IfModule concurrent_php.c>
php5_admin_value open_basedir "/home/staging03:/usr/lib/php:/usr/local/lib/php:/tmp"
</IfModule>
<IfModule !concurrent_php.c>
<IfModule mod_php5.c>
php_admin_value open_basedir "/home/staging03:/usr/lib/php:/usr/local/lib/php:/tmp"
</IfModule>
<IfModule sapi_apache2.c>
php_admin_value open_basedir "/home/staging03:/usr/lib/php:/usr/php4/lib/php:/usr/local/lib/php:/usr/local/php4/lib/php:/tmp"
</IfModule>
</IfModule>
<IfModule !mod_disable_suexec.c>
<IfModule !mod_ruid2.c>
SuexecUserGroup staging03 staging03
</IfModule>
</IfModule>
<IfModule mod_ruid2.c>
RMode config
RUidGid staging03 staging03
</IfModule>
<IfModule itk.c>
# For more information on MPM ITK, please read:
# http://mpm-itk.sesse.net/
AssignUserID staging03 staging03
</IfModule>
</VirtualHost>
那么我应该查看哪些文件以及如何检查问题是否出在 Apache 上,因为我们有 nginx 路由到 varnish,然后路由到 Apache,所以我认为问题出在 Apache 上,但是我没有从日志中得到任何有用的信息,Apache 运行时没有任何问题,它只是没有为页面提供服务,而 Varnish 由于某种原因无法访问 Apache?
我正在运行 CENTOS 6,并且我还有另一台具有相同配置且运行良好的服务器,但是当我比较 etc 文件夹的差异时,我并没有看到任何明显的差异。
答案1
根据您的日志,我可以看到 Varnish 和 Apache 都在同一台机器上运行。Varnish 应该在端口上运行,80
而 Apache 应该在端口上运行8080
。
显然还有一个 Nginx 正在运行,所以我假设它用于 TLS 终止,在端口上运行443
。
步骤 1:确保 Apache 成功监听端口 8080
运行sudo netstat -plnt
以查明每个服务使用了哪些端口。
确保httpd
服务正在监听端口8080
,并通过运行来验证这一点curl -I localhost:8080
。
第 2 步:在 VCL 文件中添加后端的健康探测
标准 VCL 不提供针对您的默认后端的运行状况探测。使用以下 VCL 代码,您可以持续监控后端运行状况:
backend default {
.host = "127.0.0.1";
.port = "8080";
.probe = {
.url = "/";
.timeout = 2s;
.interval = 5s;
.window = 10;
.threshold = 5;
}
}
添加探测器并加载新的 VCL 后,您可以调用以下命令根据探测器检查后端的健康状况:
varnishlog -g raw -i backend_health
如果输出包含Still sick
,则表明后端不可用,并且状态代码可能会告诉您原因。
步骤 3:升级 Varnish 服务器
我忍不住注意到了RxHeader
VSL 输出中的类似术语。这清楚地表明您正在使用不再受支持的旧版 Varnish。
即使在非常老的 Varnish 版本中,也RxHeader
被替换为ReqHeader
。
我的建议:升级到Varnish 6.0 LTS。Varnish 的这个 LTS 版本经常会修复一些错误并发布安全补丁。请参阅https://www.varnish-software.com/developers/tutorials/installing-varnish-centos/了解如何在 CentOS 上安装此版本。