[Dancer-users] mysterious behavior putting Dancer app in production on Starman

[Mr. Puneet Kishor]

--
Puneet Kishor http://punkish.org
Researcher http://paleodb.org http://macrostrat.org http://carbonmodel.org
Science Fellow http://creativecommons.org
Charter Member http://osgeo.org

On Jul 15, 2011, at 3:48 PM, David Precious <davidp at preshweb.co.uk> wrote:

> On Friday 15 July 2011 02:55:55 Mr. Puneet Kishor wrote:
>> Here is the interesting thing -- if I add the -D switch to the second app
>> as well, it fails to return the polys and the points. It fails with the
>> error
>> 
>> {"error":"Warning caught during route execution: DBD::mysql::st
>> fetchall_arrayref failed: fetch() without execute() at
>> <path/to>/macrostrat.pm line 79.\n"}
>> 
>> The offending lines are
>> 
>>    71> my $sql = qq{
>>    72>    ..
>>    73>
>>    74>
>>    75> };
>>    76>
>>    77> my $sth = $dbh->prepare($sql);
>>    78> $sth->execute();
>>    79> my $res = $sth->fetchall_arrayref({});
>> 
>> The above could be just correlation rather than causal, but it definitely
>> seems to be a pattern. First, this is bizarre, and why so? And, two...
>> this is totally bogus... how can execute() not take place above? Perl
>> doesn't have a habit of jumping over lines, does it?
> 
> You haven't actually performed any error checking;

In a later email I did report that --

> Paul Findlay's advice, I launched my offending app with the following invocation
>
>   $DBI_TRACE=2=logs/dbi.log plackup -E production -p 5001 -s Starman -w 10 -a bin/app.pl
>
> And, following is what stood out to me as the potential culprit in the log file
>
>   > Handle is not in asynchronous mode error 2000 recorded: Handle is 
>   > not in asynchronous mode
>   >    !! ERROR: 2000 CLEARED by call to fetch method
>
> (I am shooting in the dark here) I believe Dancer uses a lot of global variables. 
> Would that be connected to this error? On occasion, I am also seeing another 
> mysterious behavior, so mysterious that I feel I am smoking something"

I posted this question on perlmonks as well, and there has been a little discussion, but nothing conclusive yet. [http://www.perlmonks.org/index.pl?node_id=914782]. I am going to try turning on the async feature in DBI and see if that make any difference.


> either make sure RaiseError 
> is enabled on your database handle, or check for errors, e.g.:
> 
>  $sth->execute()
>      or die "Failed to execute query - " . $dbh->errstr;
> 
> As for why the behaviour changed when you selected the production environment, 
> perhaps it's down to differing settings in enviroments/development.yml and 
> environments/production.yml ?

The development.yml and production.yml settings are identical in all meaningful ways, as far as I can tell. The only differences are the ones that dancer -a cooks up when creating a bare shell of an app... Different warning levels, warning targets, and that is about it.

The only difference I can see is that with -D switch the app runs in the background, and I get no diagnostic messages. Btw, does Starman (or plackup) support logging error and accept requests like Apache does?

> 
> 
> -- 
> David Precious  ("bigpresh")
> http://www.preshweb.co.uk/
> 
>   "Programming is like sex. One mistake and you have to support
>   it for the rest of your life". (Michael Sinz)

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