[mapserver-dev] When to mark an error as "reported"?

Fri Jan 5 07:38:04 PST 2018

Hallo Steve,

sorry for the late answer. A simple example is using a not existing map file:

The first request gives a correct error message and HTTP status 200:
# LANG=C wget -O- 'http://localhost/cgi-bin/mapserv.fcgi?map=/doesnotexist'
--2018-01-05 16:02:05--  http://localhost/cgi-bin/mapserv.fcgi?map=/doesnotexist
Resolving localhost (localhost)... ::1, 127.0.0.1
Connecting to localhost (localhost)|::1|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: 'STDOUT'

<HTML>
<HEAD><TITLE>MapServer Message</TITLE></HEAD>

<BODY BGCOLOR="#FFFFFF">
msLoadMap(): Regular expression error. MS_DEFAULT_MAPFILE_PATTERN validation failed.

2018-01-05 16:02:05 (47.2 MB/s) - written to stdout [449]

While any further request just gives:
LANG=C wget -O- 'http://localhost/cgi-bin/mapserv.fcgi?map=/doesnotexist'
--2018-01-05 16:05:03--  http://localhost/cgi-bin/mapserv.fcgi?map=/doesnotexist
Resolving localhost (localhost)... ::1, 127.0.0.1
Connecting to localhost (localhost)|::1|:80... connected.
HTTP request sent, awaiting response... 500 Internal Server Error
2018-01-05 16:05:03 ERROR 500: Internal Server Error.

Apache reports:
[core:error] [pid 3019] [client ::1:38224] End of script output before headers: mapserv.fcgi

This makes mod_fcgid kill the FCGI process due to this fatal error.

The problem is that error reporting is delegated to msCGIWriteError() which immediately returns because the "isreported" field was not reset:
void msCGIWriteError(mapservObj *mapserv)
{
  errorObj *ms_error = msGetErrorObj();

  if(!ms_error || ms_error->code == MS_NOERR || ms_error->isreported) {
    /* either we have no error, or it was already reported by other means */
    return;
  }

The empty response becomes a "internal server error" since the headers are also omitted.

Regards,
Andreas

> -----Original Message-----
> From: Lime, Steve D (MNIT) [mailto:steve.lime at state.mn.us]
> Sent: Sunday, December 31, 2017 6:43 PM
> To: Eichner, Andreas - SID; mapserver-dev at lists.osgeo.org
> Subject: Re: When to mark an error as "reported"?
> 
> Hi Andreas: Do you have some examples of strange error reporting? Just
> trying to wrap my head around the issue. --Steve
> 
> ________________________________
> 
> From: mapserver-dev <mapserver-dev-bounces at lists.osgeo.org> on behalf of
> Eichner, Andreas - SID <Andreas.Eichner at sid.sachsen.de>
> Sent: Wednesday, December 27, 2017 4:23:42 AM
> To: mapserver-dev at lists.osgeo.org
> Subject: [mapserver-dev] When to mark an error as "reported"?
> 
> Hi devs,
> 
> I just found that msResetErrorList() in maperror.c does not reset the
> "isreported" field to MS_FALSE. This can cause strange error reporting
> behavior when in FastCGI mode. While checking the uses of this field I
> found that msWriteError() and msWriteErrorXML() mark errors as reported
> while msWriteErrorImage() does not.
> The problem is that msWriteErrorImage() does not access the errorObj
> directly but uses msGetErrorString(). So my question is: is it OK to let
> msGetErrorString() mark the errors as reported or should this be done in
> msWriteErrorImage()?
> I think it's truly a bug but I'm not sure what the best solution would
> be. Any ideas?
> 
> Regards,
> Andreas
> 
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