File does not exist: 500 read failed

CColin has asked for the wisdom of the Perl Monks concerning the following question:

Hi Am getting an intermittent error on a script calling an API service that has worked ok in the past - error message as follows:

Unsuccessful stat on filename containing newline at /usr/local/share/p
+erl/5.8.8/XML/Simple.pm line 939.
File does not exist: 500 read failed:
[error relating to failure of line in program reproduced in snippet be
+low]
[download]

The context is where the subroutine calling the API service fails (using XML::Simple to parse the returned object

my $response = $userAgent->request($request);
my $som=$response->{'_content'};
#print Dumper(\$som);
my $result = XMLin($som);  # Line where failure occurs.
[download]

I'm assuming if the sub XMLin failed that the file was not found? However, I'm not familiar with what the error message means exactly, tried googling didn't get far. What should I do to get to the bottom of this? Also, at the moment the program crashes out if the error is encountered. Any tips on catching this particular error and continuing appreciated. Thanks Colin

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Re: File does not exist: 500 read failed by plobsing (Friar) on Dec 07, 2007 at 14:01 UTC
Looks like your useragent response was `500 read failed: [error relating to failure of line in program reproduced in snippet be +low]` [download] You should validate responses before trying to parse it as XML (it notices its not XML and thinks its a filename). Or you could look at this XML::Simple(ERROR_HANDLING)	[reply] [d/l]
Re^2: File does not exist: 500 read failed by CColin (Scribe) on Dec 07, 2007 at 14:46 UTC
Ok - Thanks; the question then is what to do about the `500 read failed:` message if that is the cause of all the trouble - what does it mean? Colin	[reply] [d/l]
Re^3: File does not exist: 500 read failed by plobsing (Friar) on Dec 07, 2007 at 15:07 UTC
Depends on what protocol you are using. If its HTTP (and what isn't these days?), then there's been an "internal server error". Perhaps the webservice you are trying to use has a bug. Perhaps you are sending it bad data and its not catching it until it makes thinks mess up. In any case HTTP 500 means that theres an error on the other end. Maybe you should have a second look at the API.	[reply]
Re: File does not exist: 500 read failed by Herkum (Parson) on Dec 07, 2007 at 16:45 UTC
`Unsuccessful stat on filename containing newline...` [download] This means that the XML::Simple module is taking your $som variable and assumes that it is a file path because it is invalid XML. You need to validate the data that receive from the API service. A simple solution would be, `use English qw( -no_match_vars ); my $result; eval { $result = XMLin($som); } if ($EVAL_ERROR) { die "Invalid XML retrieved. The error was " . $EVAL_ERROR . "\n"; }` [download] Also don't refer to internal values for a object ESPECIALLY when it already has an interface! `## GOOD my $som=$response->content; ## BAD!!! my $som=$response->{'_content'};` [download]	[reply] [d/l] [select]
Re^2: File does not exist: 500 read failed by CColin (Scribe) on Dec 07, 2007 at 16:54 UTC
Thanks. Speed is of the essence on this service, will using "eval" put any sort of time overhead on the function? Colin	[reply]
Re^3: File does not exist: 500 read failed by ikegami (Patriarch) on Dec 07, 2007 at 17:14 UTC
Inappropriately named `eval BLOCK` is very different from `eval EXPR`. `eval EXPR` invokes the Perl parser to parse and execute EXPR. This should be avoided whenever possible. `eval BLOCK`, the function used in the parent, is the benign construct known as `try` in other languages. See `eval`.	[reply] [d/l] [select]