HAproxy：OPTIONS和POST方法的不同的503错误文件 [英] HAproxy: different 503 errorfile for OPTIONS and POST methods
问题描述
我们有一个Web应用程序使用对在不同域（ - > CORS需要）上运行的后端的Ajax调用。
后端由一个 HAproxy 1.4.22 和多个Wildfly（在OpenShift PaaS上运行）组成。如果没有Wildfly可用（例如在维护期间），HAproxy为每个请求或配置的错误文件提供503。到目前为止这么好...
这是一个问题，Web应用程序根据被拒绝的后端请求（503）正确显示维护模式，因为浏览器首先发送一个OPTIONS请求（preflight），并获得一个503。这最终导致浏览器不会将这个状态代码反映到JavaScript中执行的ajax调用（我们总是将状态代码0作为响应，因为浏览器将其解释为预检的致命失败并拒绝任何访问）。
这个故事不是新的，在stackoverflow有很多帖子。
那么如何解决这个问题呢？ 我的想法是提供两个不同的错误文件（HAproxy语言中的错误文件） - 一个服务OPTIONS请求，内容为HTTP / 1.1 200 OK .... Access-Control-Allow-Origin：*。 ...在浏览器中传递预检检查，然后一个错误文件为POST请求提供内容HTTP / 1.1 503 .....，以使浏览器真正反映ajax响应中的状态503。
全球
maxconn 256
默认值
模式http
日志全局
选项httplog
...
listen express 127.4.184.2:8080
acl is_options方法OPTIONS
acl is_post方法POST
错误文件503 /var/lib/openshift/564468c90c1e66c7f2000077/app-root/runtime/repo/503.http如果is_post
错误文件503 / var / lib / openshift / 564468c90c1e66c7f2000077 / app-root / runtime / repo / options.http if is_options
option httpchk GET /
http-check expect rstatus 2 .. | 3 .. | 401
balance leastconn
server local-gear 127.4.184.1:8080 check fall 2 rise 3 inter 2000 cookie local-564468c90c1e66c7f2000077
我理解这不能工作，因为 errorfile 不允许如果< condition> / p>
我如何实现我的愿望行为？如果有人有另一个解决方案来解决这个Maintanace模式任何想法...
提前感谢！
发现了一个好的解决方案：
- 定义两个后端（因此将listen部分分成frontend li>
- 前端部分检查请求方法，并使用一个后端来回答OPTIONS请求，并使用一个后端来回答所有其他请求。
- 第一个定义的后端用于回答所有OPTIONS请求与200：这可以用一个错误文件，如果我们不列出任何服务器在这一部分，这个后端被标记为Down，因此响应，因此错误文件
- 第二个定义的后端保留为真实后端，并在真实服务器关闭的情况下响应（也就是我们发送200返回到OPTIONS请求）
HAproxy.cfg ：
全球
maxconn 256
默认值
模式http
日志全局
选项httplog
选项dontlognull
maxconn 128
...
$ b b前端平衡器
bind 127.8.155.130:8080
模式http
acl is_options方法选项
use_backend cors_backend if_options
default_backend business_backend
后端cors_backend
errorfile 503 options.http
backend business_backend
errorfile 503 503.http
server ...
server ...
options.httpHTTP / 1.1 200 OK
访问控制允许标头：Origin，Accept，X-Session_id，Content-Type
访问控制-Allow-Origin：*
Access-Control-Allow-Credentials：true
Access-Control-Max-Age：86400
访问控制允许方法：HEAD，DELETE，POST， GET，OPTIONS，PUT
连接：close
[空行]
br>
503.httpHTTP / 1.1 503服务不可用
Cache-Control：no-cache
Access-Control-Allow-Origin：*
Connection：close
[空行]
还有一个额外的冒险：这个配置为HAproxy自动提供所有的OPTIONS请求 - 即使是CORS支持！
We have a Web application using ajax calls to a backend running on different domain (-> CORS needed). The backend consists of a HAproxy 1.4.22 and then multiple Wildflys (running on OpenShift PaaS). In case no Wildfly is available (e.g. during "Maintenance"), HAproxy serves 503 to every request or the configured errorfile. So far so good...
This is a problem for the Web application to properly visualise "Maintenance Mode" according to a rejected backend request (with 503), because the browser first sends an OPTIONS request (preflight) and gets already a 503 to it. This ends up that the Browser does not reflect this status code to the performed ajax call in JavaScript (we get always status code 0 as response because the browser interpret it as fatal failure of preflight and denies any access). This story is not new and there are many posts at stackoverflow.
So how to solve this problem? My idea is to deliver two different errorfiles ("errorfile" in HAproxy language) - one serving OPTIONS requests with content "HTTP/1.1 200 OK.... Access-Control-Allow-Origin: *...." to pass the preflight check in the browser, then one errorfile serving the POST requests with content "HTTP/1.1 503 ....." to let the browser really reflect the status 503 in the ajax response. However, I am not able to get this running.
global maxconn 256 defaults mode http log global option httplog ... listen express 127.4.184.2:8080 acl is_options method OPTIONS acl is_post method POST errorfile 503 /var/lib/openshift/564468c90c1e66c7f2000077/app-root/runtime/repo/503.http if is_post errorfile 503 /var/lib/openshift/564468c90c1e66c7f2000077/app-root/runtime/repo/options.http if is_options option httpchk GET / http-check expect rstatus 2..|3..|401 balance leastconn server local-gear 127.4.184.1:8080 check fall 2 rise 3 inter 2000 cookie local-564468c90c1e66c7f2000077I understand that this cannot work because errorfile does not allow the
if <condition>variant.How can I achieve my wished behaviour? And if someone has another solution to solve this "Maintanace Mode" / CORS problem, I am open for any idea...
Thanks in advance!
解决方案I found a good solution:
- define two "backends" (therefore split the "listen" section into "frontend" and "backend"
- The "frontend" section checks for the request method and uses one "backend" to answer OPTIONS request and one "backend" to answer all others.
- The first defined "backend" is used to answer all OPTIONS requests with 200: This can be done with an errorfile and if we do not list any server in this section, this "backend" is marked as Down and responses therefore the errorfile (in which we send 200 back to the OPTIONS request).
- The second defined "backend" stays for the "real" backend and responds - in case the real servers are down - also the content from an errorfile.
- In the errorfiles, we can add the CORS headers.
HAproxy.cfg:
global
maxconn 256
defaults
mode http
log global
option httplog
option dontlognull
maxconn 128
...
frontend balancer
bind 127.8.155.130:8080
mode http
acl is_options method OPTIONS
use_backend cors_backend if is_options
default_backend business_backend
backend cors_backend
errorfile 503 options.http
backend business_backend
errorfile 503 503.http
server ...
server ...
options.http
HTTP/1.1 200 OK
Access-Control-Allow-Headers: Origin, Accept, X-Session_id, Content-Type
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true
Access-Control-Max-Age: 86400
Access-Control-Allow-Methods: HEAD, DELETE, POST, GET, OPTIONS, PUT
Connection: close
[empty line]
503.http
HTTP/1.1 503 Service Unavailable
Cache-Control: no-cache
Access-Control-Allow-Origin: *
Connection: close
[empty line]
There is one additional adventage: This configuration serves all OPTIONS requests autonomeously by HAproxy - even with CORS support!
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