NAME¶
SOAP::Trace - used only to manage and manipulate the runtime tracing of
execution within the toolkit
DESCRIPTION¶
This class has no methods or objects. It is used only to manage and manipulate
the runtime tracing of execution within the toolkit. In absence of methods,
this section reviews the events that may be configured and the ways of
configuring them.
SYNOPSIS¶
Tracing is enabled by the SOAP::Lite import method. This is usually done at
compile-time, though it may be done explicitly by calling import directly. The
commands for setting up tracing start with the keyword +trace. Alternately,
+debug may be used; the two are interchangeable. After the initial keyword,
one or more of the signals detailed here may be specified, optionally with a
callback to handle them. When specifying multiple signals to be handled by a
single callback, it is sufficient to list all of them first, followed finally
by the callback, as in:
use SOAP::Lite +trace =>
method => fault => \&message_level,
trace => objects => \&lower_level;
In the fragment, the reference to message_level is installed as the callback for
both method and fault signals, while lower_level is installed for trace and
object events. If callbacks aren't explicitly provided, the default tracing
action is to log a message to Perl's STDOUT file descriptor. Callbacks should
expect a one or more arguments passed in, though the nature of the arguments
varies based on the signal.
Any signal can be disabled by prefacing the name with a hyphen, such as -result.
This is useful with the pseudosignal "all," which is shorthand for
the full list of signals. The following fragment disables only the two
signals, while still enabling the rest:
SOAP::Lite->import(+trace => all => -result => -parameters);
If the keyword +trace (or +debug) is used without any signals specified, it
enables all signals (as if all were implied).
The signals and their meaning follow. Each also bears a note as to whether the
signal is relevant to a server application, client application, or both.
TRACE SIGNALS¶
- transport Client only
- Triggered in the transport layer just before a request is sent and
immediately after a response is received. Each time the signal is sent,
the sole argument to the callback is the relevant object. On requests,
this is a HTTP::Request object; for responses, it's a HTTP::Response
object.
- dispatch Server only
- Triggered with the full name of the method being dispatched, just before
execution is passed to it. It is currently disabled in SOAP::Lite
0.55.
- result Server only
- Triggered after the method has been dispatched and is passed the results
returned from the method as a list. The result values have not yet been
serialized when this signal is sent.
- parameters Server only
- Triggered before a method call is actually dispatched, with the data that
is intended for the call itself. The parameters for the method call are
passed in as a list, after having been deserialized into Perl data.
- headers Server only
- This signal should be for triggering on the headers of an incoming
message, but it isn't implemented as of SOAP::Lite 0.55.
- objects Client or server
- Highlights when an object is instantiated or destroyed. It is triggered in
the new and DESTROY methods of the various SOAP::Lite classes.
- method Client or server
- Triggered with the list of arguments whenever the envelope method of
SOAP::Serializer is invoked with an initial argument of method. The
initial string itself isn't passed to the callback.
- fault Client or server
- As with the method signal earlier, except that this signal is triggered
when SOAP::Serializer::envelope is called with an initial argument of
fault.
- freeform Client or server
- Like the two previous, this signal is triggered when the method
SOAP::Serializer::envelope is called with an initial parameter of
freeform. This syntax is used when the method is creating SOAP::Data
objects from free-form input data.
- trace Client or server
- Triggered at the entry-point of many of the more-significant functions.
Not all the functions within the SOAP::Lite classes trigger this signal.
Those that do are primarily the highly visible functions described in the
interface descriptions for the various classes.
- debug Client or server
- Used in the various transport modules to track the contents of requests
and responses (as ordinary strings, not as objects) at different points
along the way.
EXAMPLES¶
SELECTING SIGNALS TO TRACE¶
The following code snippet will enable tracing for all signals:
use SOAP::Lite +trace => 'all';
You can disable tracing for a set of signals by prefixing the signal name with a
hyphen. Therefore, if you wish to enable tracing for every signal EXCEPT
transport signals, then you would use the code below:
use SOAP::Lite +trace => [ qw(all -transport) ];
LOGGING SIGNALS TO A FILE¶
You can optionally provide a subroutine or callback to each signal trace you
declare. Each time a signal is received, it is passed to the corresponding
subroutine. For example, the following code effectively logs all fault signals
to a file called fault.log:
use SOAP::Lite +trace => [ fault => \&log_faults ];
sub log_faults {
open LOGFILE,">fault.log";
print LOGFILE, $_[0] . "\n";
close LOGFILE;
}
You can also use a single callback for multiple signals using the code below:
use SOAP::Lite +trace => [ method, fault => \&log ];
LOGGING MESSAGE CONTENTS¶
The transport signal is unique in the that the signal is not a text string, but
the actually HTTP::Request being sent (just prior to be sent), or
HTTP::Response object (immediately after it was received). The following code
sample shows how to make use of this:
use SOAP::Lite +trace => [ transport => &log_message ];
sub log_message {
my ($in) = @_;
if (class($in) eq "HTTP::Request") {
# do something...
print $in->contents; # ...for example
} elsif (class($in) eq "HTTP::Response") {
# do something
}
}
ON_DEBUG¶
The "on_debug" method is available, as in:
use SOAP::Lite;
my $client = SOAP::Lite
->uri($NS)
->proxy($HOST)
->on_debug( sub { print @_; } );
ACKNOWLEDGEMENTS¶
Special thanks to O'Reilly publishing which has graciously allowed SOAP::Lite to
republish and redistribute large excerpts from
Programming Web Services
with Perl, mainly the SOAP::Lite reference found in Appendix B.
COPYRIGHT¶
Copyright (C) 2000-2004 Paul Kulchenko. All rights reserved.
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
AUTHORS¶
Paul Kulchenko (paulclinger@yahoo.com)
Randy J. Ray (rjray@blackperl.com)
Byrne Reese (byrne@majordojo.com)