[Xapian-discuss] Dreaded "Premature end of script headers: omega"...

[Jim]

Olly Betts wrote:
> On Mon, May 05, 2008 at 08:57:42PM -0300, Bill Hutten wrote:
>   
>> I've (almost) successfully setup Xapian and Omega on a Linux machine -  
>> the index has been created successfully, and using omega from the  
>> command line works perfectly...
>>     
>
> OK, that's good so far.
>
>   
>> However - it's not working as a CGI - I consistently get "Premature  
>> end of script headers: omega" in the Apache error log.
>>     
>
> In case you aren't aware, this generally means "script died before
> writing any output" (strictly speaking, before writing a blank line to
> end the headers, but it's rare to die halfway through the headers for
> a CGI which works elsewhere.
>
>   
>> I've placed the "omega" executable in the cgi-bin directory, along  
>> with the "omega.conf" file.  (Is the .conf file required to be  
>> "beside" the omega executable)?
>>     
>
> It's not *required* to be there, but that is one of the places it can
> be.  For more details, see the "omega configuration" section here:
>
> http://xapian.org/docs/omega/overview.html
>
>   
>> I've also checked permissions - my  
>> cgi-bin directory is owned by "southshore.psaserv", as is the omega  
>> executable and the omega.conf.
>>
>> I'm obviously missing something... anyone care to point it out to me?   
>> I've checked the mailing list archives and the only suggestion was to  
>> make sure that the permissions on the omega executable matched the  
>> permissions on the cgi-bin directory - but they seem to match fine...
>>     
>
> You've already ruled out the Omega-specific parts (since Omega runs from
> the command line), so it's really an exercise in generic CGI debugging
> at this point.  Unfortunately, this sort of thing isn't easy to debug
> remotely as I don't know anything about how your server is set up.
>
> You need to look at differences between your environment and that
> which the CGI gets run as from the webserver.  Environment variables
> are one issue.  Another is the user/group which runs CGI scripts.
>
> Some things to check:
>
> * If you're able, try running omega *as the user which runs CGI scripts*
>   from your shell (e.g. using su).  You'll probably need root access for
>   that though.
>
> * Is the omega CGI binary readable and executable by the user which CGI
>   scripts run as?
>
> * Did you symlink the omega binary to the CGI directory?  Some servers
>   don't like symlinked CGI scripts.
>
> * Write a simple CGI script to dump environment variables and put it in
>   the same CGI directory as omega, with the same permissions.  Assuming
>   it runs, compare output with printenv in your shell.  Something as
>   simple as this will probably do:
>
> #!/bin/sh
> echo "Content-Type: text/plain"
> echo
> printenv
>
>   Consider any differences carefully, but one particular thing to looks
>   for - Omega should get an rpath set if xapian-core isn't on the
>   standard library search path, but if you needed to set LD_LIBRARY_PATH
>   for some reason, you'll need to ensure that this is set when it is run.
>
>   
It shouldn't cause this error, but you may want to change the name to 
omega.cgi and try it.  Some apache configurations want cgi scripts to 
have the extension cgi.

I had this problem with a Debian install a while back.  For some reason 
Apache never would actually execute a program.  I finally gave up after 
a couple of weeks and installed Ubuntu instead. 

Jim.