Thanks a lot Thierry, that was it, changing to http-request solved my
issue.
I am now able to leverage a fully dynamic backend :)
Thanks
Sachin
On 7/21/16, 10:52 PM, "thierry.fourn...@arpalert.org"
<thierry.fourn...@arpalert.org> wrote:
>On Tue, 19 Jul 2016 15:28:25 +0530
>Sachin Shetty <sshe...@egnyte.com> wrote:
>
>> Hi,
>>
>> We always had a unique requirement of picking a backend based on
>>response
>> from a external http service. In the past we have got this working by
>> routing requests via a modified apache and caching the headers in maps
>>for
>> further request, but now I am trying to simplify our topology and
>>trying to
>> get this done using just haproxy and lua.
>>
>> I am running in to some problems:
>>
>> Lua method:
>>
>> function choose_backend(txn)
>>
>> local host = txn.http:req_get_headers()["host"][0]
>>
>> core.Alert("Getting Info:" .. host)
>>
>> local sock = core.tcp()
>>
>> sock:connect("127.0.0.1", 6280)
>>
>> sock:send("GET /eos/rest/private/gds/l1/1.0/domain/" .. host ..
>> "\r\n")
>>
>> result = sock:receive("*a")
>>
>> sock:close()
>>
>> core.Alert("Received Response:" .. result .. "<")
>>
>> core.set_map("/tmp/proxy_webui.map", host, result)
>>
>> core.Alert("Map Set:" .. host .. "-->" .. result .. "<")
>>
>> end
>>
>>
>>
>> core.register_action("choose_backend", { "http-req" }, choose_backend)
>>
>>
>> Haprpxy Conf:
>>
>> frontend luatest
>>
>> mode http
>>
>> maxconn 10000
>>
>> bind *:9000
>>
>>
>>
>> use_backend %[hdr(host),lower,map(/tmp/proxy_webui.map)] if
>>FALSE #
>> To declare the map
>>
>>
>> http-request lua.choose_backend
>>
>>
>> tcp-request content capture hdr(host),map(/tmp/proxy_webui.map)
>>len
>> 80
>>
>> acl is_ez_pod capture.req.hdr(0) http://127.0.0.1:6280
>>
>> use_backend ez_pod if is_ez_pod
>>
>>
>>
>>
>>
>> backend ez_pod
>>
>> server ez_pod 192.168.56.101:6280 maxconn 2
>>
>>
>>
>>
>>
>> There are some issues:
>> 1. I do see Map Set called correctly in the logs, but the haproxy
>>capture
>> does not find the key in the map for the first request. Is this related
>>to
>> async execution of luna routine?
>
>
>Hi,
>
>The processing of the request by haproxy is pending while the execution
>of the lua action.
>
>The execution of "tcp-request content" directives are done before the
>execution of "http-request". So HAProxy executes first the capture and
>them the action which populate the map.
>
>Normally, HAProxy display a warning when it start, if it detects a
>configuration order different than a execution order. Try to replace the
>"tcp-request" by "http-request".
>
>
>> 2. I expected subsequent requests to see the value atleast, but even
>>that is
>> not consistent, some request see the value in the map and some don¹t
>> Is there a better way to do this?
>
>
>It seems that you use a good way to do this.
>
>
>> I already found that I cannot invoke the
>> luna routine with use_backend because yield is not allowed in a sample
>>fetch
>> context.
>
>
>Yes, the usage of core.tcp() require some yields, and haproxu doesn't
>support yield during the execution of sample-fetches. For bypassing
>this problem, I use variables. I store the expected result in a
>variable during the execution of the action, and I use these variable
>with the use_backend directive.
>
>
>Thierry
>
>
>> What would be the best way to achieve this, our requirement is similar
>>to
>> what can be done with redis+nginx here:
>> http://openresty.org/en/dynamic-routing-based-on-redis.html except for
>>we
>> have an http service that decides the backend instead of a redis
>>service.
>>
>> Thanks
>> Sachin
>>
>>
