Hello,
Thanks for all your help. Any rough estimate on when the patch for doing DNS
resolutions during runtime with asynchronous methods might be out?
-Mrunmayi
On Saturday, May 30, 2015 2:47 AM, Thierry FOURNIER
<tfourn...@haproxy.com> wrote:
On Sat, 30 May 2015 00:25:59 +0000 (UTC)
Mrunmayi Dhume <mrunmayi.dh...@yahoo.com> wrote:
> Hello Thierry,
> This seems to be what we are looking for, however it doesn't seem to work as
> expected. When we use your example as is, it seems to fail with a 500 error.
> When we switch to using a IP address, it works, so it seems like DNS
> resolution is a problem?
Yes, haproxy can not execute DNS résolutions while is running. It does
DNS resolution only during the configuration parsing. Its because the
standard DNS resolution are a synchronous process, and the HAProxy
architecture does not accept synchronous processes.
Note that a patch is currently in development for doing DNS resolutions
during the runtime with asynchronous methods.
As per this doc -
http://cbonte.github.io/haproxy-dconv/configuration-1.6.html#4-option%20http_proxy
http-proxy mode does not accept hostname, instead it only accepts IP.
> The below example works:
> core.register_fetches("choose_backend", function(txn) if
>txn.sf.req_fhdr(Host) == 'example.test.com' and txn.sf.req_path ==
>'/test' then return "1.1.1.1" else if [...] end return
>"default_backend" end);
> In the haproxy configuration file, you must load the lua file, and usethe new
> declared fetch in your frontend:
> global [...] lua-load your-lua-file.lua [...]
> listen your_frt [...] option http_proxy http-request set-uri
>http://%[lua.choose_backend]%[url]
> We don’t want to have to specify the IP as that means that we will have to
> perform some sort of dns resolution in lua. Can you suggest an alternative?
Actually, you can use maps to do this. A map is a file containing a
name and his correspondance. You can put a hostname and the associated
ip.
This map can be updated throught the HAProxy's socket (without
restarting HAProxy). This is not a real DNS Resolution, you must kown
the full list of your domains.
Thierry
> Thanks!
> -Mrunmayi
>
>
> On Wednesday, May 27, 2015 1:50 AM, Thierry FOURNIER
><tfourn...@haproxy.com> wrote:
>
>
> On Tue, 26 May 2015 21:39:23 +0000 (UTC)
> Mrunmayi Dhume <mrunmayi.dh...@yahoo.com> wrote:
>
> > Thanks for your detailed reply Thierry. While this approach would solve the
> > aspect of choosing the backend dynamically we still need to explicitly
> > define each backend server separately in the haproxy config file. Our
> > use-case involves having 100+ backends and we would prefer not to
> > complicate the config file by defining each backend server as it is not
> > easy to maintain. We prefer to set it based on incoming http request
> > information like path or host header and keep haproxy config file simple
> > with just listen and FE directives and of course single default backend
> > server
>
>
> Hi,
>
> HAProxy does not permit to choose the destination IP and PORT.
>
> But, maybe I have an ugly solution to your problem.
>
> You can try to deal with the option "option http_proxy". This option
> understand the base proxy requests.
>
> You create a "listen" section which use Lua for rewriting the path of
> the HTTP request like this:
>
> core.register_fetches("choose_backend", function(txn)
> if txn.sf.req_fhdr(Host) == 'example.test.com' and
> txn.sf.req_path == '/test' then
> return "test1. example.com:8081"
> else if
> [...]
> end
> return "default_backend"
> end);
>
> In the haproxy configuration file, you must load the lua file, and use
> the new declared fetch inyour frontend:
>
> global
> [...]
> lua-load your-lua-file.lua
> [...]
>
> listen your_frt
> [...]
> option http_proxy
> http-request set-uri http://%[lua.choose_backend]%[url]
> [...]
>
> Thierry
>
>
> > if (Host == aaa.example.com’ and path == ‘/test’) thenbackend server ==
> > test1. example.com:8081 (Origin port changed) elsif (Host ==
> > aaa.example.com’ and path == ‘/test2’) backend server == test2.
> > example.com:8080 (Origin port changed) elsif (Host == aaa.example.com’ and
> > path == ‘/test3’) backend server == xxx.example.com:9999 ((Origin host and
> > port changed)
> >
> > looking for something like the Traffic server lua api -
> > https://docs.trafficserver.apache.org/en/latest/reference/plugins/ts_lua.en.html#ts-client-request-set-url-host
> >
> > Thanks,
> > Mrunmayi
> >
> >
> >
> > On Tuesday, May 26, 2015 3:15 AM, Thierry FOURNIER
> ><tfourn...@haproxy.com> wrote:
> >
> >
> > On Fri, 22 May 2015 19:06:59 +0000 (UTC)
> > Mrunmayi Dhume <mrunmayi.dh...@yahoo.com> wrote:
> >
> > > Hello,
> > > I am using haproxy-1.6 with Lua. I have a use-case where I want to set
> > > the destination (backend server) very dynamically, based on certain layer
> > > 7 information (I am trying to avoid updating haproxy configuration and
> > > make it complicated with a ~100 domain names and their corresponding
> > > backend server name and do a map lookup, I want lua to do it )
> > > eg: from lua, based on certain layer 7 information I want to change the
> > > backend server (set destination) it should connect to..
> > > if Host is ‘example.test.com’; then backend is test1.server.com elsif
> > >Host is ‘example2.test.com; then backend is test2.server.com I want to
> > >keep the haproxy config simple and have only the Listen directive listed
> > >and take more control of the request flow from the LUA code.
> > > The ATS traffic server does provide such functionality through the LUA
> > > API hook to override backend server dynamically from Lua end
> > > if ts.client_request.header[Host] == 'example.test.com' then
> > >ts.client_request.set_url_host(
> > >test1.server.comts.client_request.set_url_port(80)elsif
> > >ts.client_request.header[Host] == 'example2.test.com' then
> > >ts.client_request.set_url_host( test2.server.com )
> > >ts.client_request.set_url_port(80)end
> > > Is it possible to do the same using Haproxy and Lua?
> >
> >
> > Hi,
> >
> > Yes, you can, but the way is a little bit different.
> >
> > You must create a new sample fetch in Lua. This fetch executes the
> > analysis of your HTTP resuest and returns the backend name. The
> > following code (untested) must set in a lua file:
> >
> > core.register_fetches("choose_backend", function(txn)
> > if txn.sf.req_fhdr(Host) == 'example.test.com' then
> > return "backend1"
> > else if txn.sf.req_fhdr(Host) == 'other.domain.com' then
> > return "backend2"
> > [...]
> > end
> > return "default_backend"
> > end);
> >
> > In the haproxy configuration file, you must load the lua file, and use
> > the new declared fetch inyour frontend:
> >
> > global
> > [...]
> > lua-load your-lua-file.lua
> > [...]
> >
> > frontend your_frt
> > [...]
> > use_backend %[lua.choose_backend]
> > [...]
> >
> > Note that your example code seem to choose a backend regarding only the
> > header "host". In this case, the lua is useless, you can use the "maps"
> > to choose your backend. The configuration looks like this:
> >
> > frontend yur_frt
> > [...]
> > use_backend %[req.fhdr(host),tolower,map(host_to_bck.map,default)]
> > [...]
> >
> > The "default" argument is the name of the default backend. And the file
> > "host_to_bck.map" contains a mapping between the hostnames (in lower
> > case) and the backend names:
> >
> > example.test.com backend1
> > other.domain.com backend2
> >
> > etc...
> >
> > Thierry
> >
> >
> > >
> > > Thank you,
> > > Mrunmayi
> >
> >
>
>
>
>
