Re: cannot always fetch parent article

[Katsumi Yamaoka <yamaoka@jpl.org>]

[-- Attachment #1: Type: text/plain, Size: 1750 bytes --]

>>>>> Ansgar Burchardt wrote:

> newszilla.xs4all.nl and news.arcor.de both seem to run Diablo.

> I found an interesting post about this [1]: apparently Diablo will
> forward a request by Message-Id to a different system, which likely has
> different article numbers.  If load balancing is used this might explain
> why I get sometimes different article numbers.

I see.  So, we should use only Message-IDs to refer to articles
for such news servers.

[...]

> If I post a followup to an article to a different group (e.g. a random
> *.test group) and then try to fetch the parent article it works without
> problems.  The problem only occurs if the parent was posted in the
> same group as the followup and Gnus tries to guess the article number.
> If Gnus behaved as in the first case, everything would be fine.

I studied how Gnus refers to parent articles, and realized that
Gnus uses an article number only when a parent article is in the
current group.  Could you try the patch attached below?

The new variable `nntp-xref-number-is-evil' controls whether Gnus
ignores article numbers in the Xref header.  This is a server
variable, so you can set it per server as follows:

(setq gnus-select-method
      '(nntp "newszilla"
	     (nntp-address "newszilla.xs4all.nl")
	     (nntp-xref-number-is-evil t)
	     ...
	     ))

Or you can simply use the following if your servers are all Diablo:

(setq nntp-xref-number-is-evil t)

Note that the number of a parent article in the current group
will be displayed as a negative number if you've configured
`gnus-summary-line-format', `gnus-summary-mode-line-format' or
`gnus-article-mode-line-format' to do so.

I verified the patch can be applied to both Gnus v5.11 of Emacs
22.1 and No Gnus v0.7.


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: Type: text/x-patch, Size: 1032 bytes --]

--- nntp.el~	2007-07-18 12:07:39 +0000
+++ nntp.el	2007-08-08 10:12:33 +0000
@@ -203,6 +203,14 @@
 server there that you can connect to.  See also
 `nntp-open-connection-function'")
 
+(defvoo nntp-xref-number-is-evil nil
+  "*If non-nil, Gnus never trusts article numbers in the Xref header.
+Some news servers, e.g., ones running Diablo, run multiple engines
+having the same articles but article numbers are not kept synchronized
+between them.  If you connect to such a server, set this to t, and Gnus
+never uses article numbers (that appear in the Xref header and vary by
+which engine is chosen) in order to refer to articles.")
+
 (defvoo nntp-coding-system-for-read 'binary
   "*Coding system to read from NNTP.")
 
@@ -1702,7 +1710,8 @@
 		    (match-string 1 xref))
 		   (t "")))
 	  (cond
-	   ((and (setq xref (mail-fetch-field "xref"))
+	   ((and (not nntp-xref-number-is-evil)
+		 (setq xref (mail-fetch-field "xref"))
 		 (string-match
 		  (if group
 		      (concat "\\(" (regexp-quote group) "\\):\\([0-9]+\\)")