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From: Adam Kocoloski <kocolosk@apache.org>
To: user@couchdb.apache.org
In-Reply-To: <b7cd8ed10906120303v418f7d06k9bbefdfb912ad616@mail.gmail.com>
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Subject: Re: problem with replication + nginx proxy
Date: Fri, 12 Jun 2009 10:04:39 -0400
References: <b7cd8ed10906120303v418f7d06k9bbefdfb912ad616@mail.gmail.com>

On Jun 12, 2009, at 6:03 AM, Benoit Chesneau wrote:

> Hi all,
>
> I'm trying to replicate a source database behind a nginx proxy. All
> docs seem replicated in target db but replication never ending.
>
> Configuration of nginx is :
> server {
>        listen 88.191.73.9:80;
>        server_name nymphormation.org www.nymphormation.org;
>
>        location / {
>                proxy_pass http://127.0.0.1:5985;
>                proxy_redirect default;
>                proxy_set_header X-Orig-Host '$host:$server_port';
>
>                if ($request_uri ~* "^/$") {
>                        rewrite ^/$
> =
http://nymphormation.org/n/_design/nymphormation/_list/links/news?limit=3D=
11&descending=3Dtrue
> permanent;
>                }
>        }
>
>        location ~ ^/robots.txt {
>            root /home/nymphormation/www;
>        }
>
>   }
>
> To reproduce I just do a simple replication of
> http://nymphormation.org/n to a local db. Could the problem appear due
> to rewriting of / ?
>
>
>
> - beno=EEt

Hi Benoit, the error occurs when the replicator tries to POST to =20
_ensure_full_commit on nymphormation.org.  This POST has no body and =20
no Content-Length header, which drives nginx batty.  The response that =20=

comes back from your server is

> <html>
> <head><title>411 Length Required</title></head>
> <body bgcolor=3D"white">
> <center><h1>411 Length Required</h1></center>
> <hr><center>nginx/0.7.41</center>
> </body>
> </html>

and the replicator chokes on that because it's expecting JSON.  I =20
think nginx is being overly strict here; HTTP/1.1 does not require a =20
Content-Length header, especially for empty request bodies.

In my opinion this is a bug in nginx, not Couch.  It's particularly =20
annoying when working in Erlang because the inets HTTP client actually =20=

_strips off_ the Content-Length header if no body is present.  I'm a =20
bit confused, though, because the nginx changelog =
(http://nginx.net/CHANGES=20
) indicates that as of 0.7.25 POSTs do not require a Content-Length.

There are a few things we could do in Couch, including a) manually =20
adding the Content-Length : 0 header to the request and b) not letting =20=

ourselves get stuck in an infinite receive when ensure_full_commit =20
fails like this.  The latter we should definitely do; I'm ambivalent =20
about the former.  Best,

Adam