hgweb Odd-string length error

[Matt Mackall]

On Mon, 2014-07-21 at 16:02 -0400, Jérôme Godbout wrote:
> Here's the hex string of the batch cmd answer that failed (no other command
> are sent):
> 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
> 
> Once decoded (used Python string.decode("hex"))
> ' \xcf0y\x89\x0eP\xe5I\xc6\xb7\xee\x08\x00E\x00\x01\x08DZ@
> \x00\x80\x06\x00\x00\n\x01\x1e\xc3\n\x01\x1ef\x00P\xce5\xdd.\x91\xa2\xebP1\xfcP\x18\x00\xffR%\x00\x00HTTP/1
> .1 200 Script output follows\r\nDate: Mon, 21 Jul 2014 18:05:55
> GMT\r\nServer: Apache/2.4.9 (Win64) OpenSSL/1.0.1f\r\nContent-Length:
> 42\r\nContent-Type: application
> /mercurial-0.1\r\n\r\n779d1659558261acdbdc5a83bbd6a081b42eedfb\r\n;'

Yep, there's your problem. If I do the same dump on a working system, I
get a response with no \r before the last \n. The client-side parser for
this strips off the \n and then tries to decode it:

$ python
Python 2.7.5+ (default, Sep 17 2013, 15:31:50) 
[GCC 4.8.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import binascii
>>> binascii.unhexlify("779d1659558261acdbdc5a83bbd6a081b42eedfb\r");
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Odd-length string

Something in your stack is helpfully seasoning Mercurial's output with
some extra DOS flavor. While it might look like something we can work
around trivially, the next command we send will in fact send a strictly
binary stream with the same MIME type: changing \n to \r\n will break
things for sure.

We've seen this "Odd-length string" thing before, but it's always been
attributable to some form of stack trace or similar garbage dropping
into the stream, but this version of the problem is unique to your
environment. Proxies and FastCGI/WSGI frameworks are likely culprits.

-- 
Mathematics is the supreme nostalgia of our time.