NAME
Luka - Exception handling and reporting framework
SYNOPSIS
use Error qw(:try);
use Luka;
try {
$ftp->login("someuser", "somepass") ||
throw Luka::Exception::External
( error => $ftp->message . $@, id => "login",
context => "FTP error: couldn't login", severity => 3,
args => "user=someuser,pass=somepass" );
} catch Luka::Exception with {
my $e = shift;
$e->report;
return 17;
} catch Error with {
my $e = shift;
$e->report;
return 18;
};
DESCRIPTION
Luka is an exception handling and reporting framework. It's useful to
look at it as an event handling framework.
It comes from operational understanding of networks.
Scenario that Luka is addressing is following: on a network with
multiple hosts running multiple applications, it is very difficult to
track operational status of all the functionality that those
applications and hosts are meant to deliver. In order to make it easier,
we decided to specify the error handling and reporting data model that
each component delivering functionality has to conform to. What is a
component? In most cases, it is a script, often run from cronjob, in
some cases it is a class in an application. In all cases, a component
has to successfully complete a task on which functionality of an
application, or entire network, relies on.
It is common practice that programmers choose their way of handling
errors and reporting. Luka is an attempt to standardize that process.
Its primary goal is to make it easier for smaller number of people to
keep larger number of applications and networks running.
Policy on script error handling that Luka suggests:
NO ERROR CODES are used, instead exceptions are thrown
Already a common practice, especially in applications/components
that are not small.
Standard set of error english names is established (network connection
error)
As opposed to each network library, for example, having it's own way
to report connection error.
Page for each component (script/class) documenting relevant details
Already a common practice. Luka suggests that link to page
describing all possible errors, along with dependencies and
schedules (for components that run regularly), should exist. It is
part of the Luka event data model.
EACH time an error occurs following MUST be attempted:
1. Capture defined data set
2. Log summary to to system log
3. attempt delivery to end points
Example config
[global]
debug=0
single_char_error_code=E
single_char_success_code=I
doc_base=http://localhost/
email_domain=lists.mydomain.org
syslogopt=pid,nowait
syslogfacility=daemon
expected_ip=10.1.8
[myscript.pl]
on_success=Task completed
doc=LukaTests
about=this library does something useful
from=root@localhost
cc=me@mydomain.org
nomail=0
Example of error report
On an error caught, in syslog:
Feb 26 15:34:39 localhost myscript.pl[1298]: Luka initiating...
Feb 26 15:34:39 localhost myscript.pl[1298]: Error at line 20: Net::FTP: Bad hostname 'bla.org' at myscript.pl line 324.
Feb 26 15:34:39 localhost myscript.pl[1298]: Error report sent to myscript.pl@lists.mydomain.org,me@mydomain.org
Email headers:
From: root@localhost
To: myscript.pl@lists.mydomain.org
Cc: me@mydomain.org
Subject: [galeb][2006-2-26T15:34:42][E] Net::FTP: Bad hostname 'bla.org'
Event (used verbatim in email body):
this library does something useful
http://localhost/LukaTests#ftp_object_creation
host=galeb
hosterr=
ipaddr=10.1.8.18
time=2006-2-26T15:34:42
script=myscript.pl
path=/home/toni/dev/cvs/perl/modules/luka
line=245
pid=1298
severity=3
context=FTP error: couldn't create object
args=ftp.false
id=ftp_object_creation
error=Net::FTP: Bad hostname 'bla.org'
Trace begun at myscript.pl line 245
main::__ANON__ at /usr/local/share/perl/5.8.7/Error.pm line 372
eval {...} at /usr/local/share/perl/5.8.7/Error.pm line 371
Error::subs::try at myscript.pl line 255
main::ftp_luka_catch at myscript.pl line 123
main::__ANON__ at /usr/local/share/perl/5.8.7/Test/Exception.pm line 281
eval {...} at /usr/local/share/perl/5.8.7/Test/Exception.pm line 281
Test::Exception::lives_and at myscript.pl line 124
Example of success report
On a captured report, in syslog:
Feb 26 15:34:22 localhost myscript.pl[1273]: Luka initiating...
Feb 26 15:34:22 localhost myscript.pl[1273]: Success report sent to myscript.pl@lists.mydomain.org,me@mydomain.org
Email headers:
From: root@localhost
To: myscript.pl@lists.mydomain.org
Cc: me@mydomain.org
Subject: [galeb][2006-2-26T15:34:22][I] Task completed
Event (used verbatim in email body):
this library does something useful
http://localhost/LukaTests
host=galeb
hosterr=
ipaddr=10.1.8.18
time=2006-2-26T15:34:22
script=myscript.pl
pid=1273
LUKA EVENT DATA MODEL
Structure
ABOUT COMPONENT
\n
DOC
\n
attribute=value
attribute=value
attribute=value
attribute=attribute=value,attribute=value
attribute=value
\n
\n
STACKTRACE
Fields
ABOUT COMPONENT Comes from config file component section.
DOC Location of the documentation. Can be URL, or some other
protocol address. Can be specific to the error reported, or
component general. Comes from config file component section.
host - Name of the host where the event originates from. Collected.
hosterr - Name of the services that Luka couldn't use as expected on
the host. Collected. The only possible value is, at the moment,
*syslogd*.
ipaddr - IP address of the host. Collected. When multiple IPs
present (most cases), regular expression matching one from the
configuration file field "expected_ip" will be chosen.
time - Timestamp, conforming to RFC3339 "Date and Time on the
Internet: Timestamps", see <http://www.ietf.org/rfc/rfc3339.txt>.
Example: "2006-2-26T15:34:42". Constructed out of host time.
script - Name of the component that generated event. Collected.
pid - Process ID of the component that generated the event.
Collected from the host.
path - Path to the component that generated event. Collected. Error
event only.
line - Line number where event generation occurred. Collected. Error
event only. Error event only.
severity - Severity level of the event (ambiguous, see TODO
section). Supplied by the programmer at the location of event
creation. Error event only.
context - Descriptive text, context of the event. Specific to the
functionality that components performs from the user perspective,
rather than from the strictly technical perspective of programming
libraries. Supplied by the programmer at the location of event
creation. Error event only.
args - Arguments relevant for the event generated (passed to the
function, object). Supplied by the programmer at the location of
event creation. Error event only.
id - ID of the event. Supplied by the programmer at the location of
event creation. Matches the documentation for the component. Error
event only.
error - Technical text of the error. Supplied by the programmer at
the location of event creation. Supplement to the "context" field,
from the technical perspective, can contain error text returned by
used programming library. Error event only.
METHODS
report
Luka report to syslog what happens by default.
Aug 26 11:27:49 localhost myscript.pl[1038]: Error at line 46: Net::FTP: Bad hostname
'ftp.bla.bla' at myscript.pl line 80.
Aug 26 11:27:49 localhost myscript.pl[1038]: Error report sent to myscript.pl@lists.mydomain.org
report_success( $message )
If the $message is not supplied, value of the field "on_success" from
the component section of Luka configuration file will be used.
DIAGNOSTICS
"Luka system not functional for '%s' script. Couldn't read its section
'%s' in config file '%s'"
Throws Luka::Exception::Program exception. Luka can not deliver
event if section for given script is missing in given config.
Sections are by default named by the script name.
"Luka system disabled. Couldn't read its config file '%s': %s"
Throws Luka::Exception::Program exception. Luka can not do anything
if its config file is missing or can not be parsed. However, if
syslogd is running, it will place a warning in syslog:
Feb 26 12:26:59 localhost Luka::Conf[30438]: Luka system disabled. Couldn't read its config file 'bla.txt':
Failed to open bla.txt: No such file or directory at lib/Luka/Conf.pm line 63
"Couldn't report by email to:%s;cc:%s;from:%s"
Throws Luka::Exception::External. If MTA is not running, or if Luka
can not connect to it, stdout will receive:
ERROR: Can't connect to localhost:25
Couldn't report by email to:test@localhost;cc:toni@localhost;from:root@localhost
In the syslog, warning will be:
Feb 26 13:42:08 localhost myscript.pl[3071]: Couldn't report by email: to: myscript.pl@lists.mydomain.org,
cc: me@mydomain.org, from: root@localhost
Feb 26 13:42:08 localhost myscript.pl[3071]: Mail system reported: ERROR: Can't connect to localhost:25
CONFIGURATION
global section
Single section, applies to the host on which Luka runs.
[global]
debug=0
single_char_error_code=E
single_char_success_code=I
doc_base=http://localhost/
email_domain=lists.mydomain.org
syslogopt=pid,nowait
syslogfacility=daemon
expected_ip=10.1.8
Fields:
debug - Turns debugging mode on when set to 1.
single_char_error_code - Delivery field. Single character error
code. Default is "E". In email delivery, part of header SUBJECT
field.
single_char_success_code - Delivery field. Single character success
code. Default is "I". In email delivery, part of header SUBJECT
field.
doc_base - Event field. Base part of the DOC field in the event data
model.
email_domain Delivery field. Email. Domain part of the header TO
field.
syslogopt *$logopt* options passed to Sys::Syslog's *openlog*
function
syslogfacility *$facility* option passed to Sys::Syslog's *openlog*
function
expected_ip Event field. See above IPADDR field in the event data
model. Luka discovers IPs on the host. Since multiple IPs are
present in most cases, regular expression matching one from this
configuration file field *expected_ip* will be selected. This would
be a drawback on a host with many interfaces, and solution with
fixed IP would be a lot more efficient in that case.
component sections
One or more sections, applies to components programmed to use Luka.
[myscript.pl]
on_success=Task completed
doc=LukaTests
about=this library does something useful
from=root@localhost
cc=me@mydomain.org
nomail=0
Fields:
on_success - Delivery field. In email delivery, part of header
SUBJECT field.
doc - Event field. Component part of the DOC field in the event data
model.
about - Event field. See above COMPONENT field in the event data
model.
from - Delivery field. Email. Header FROM field.
cc - Delivery field. Email. Header CC field.
nomail - If set to 1, event will not be delivered via email.
DEPENDENCIES
* Error - implementation of try/catch syntax
* Exception::Class - easy definition of hierarchy of exception classes
* Config::IniFiles - config file handling
* Sys::Syslog - writing to syslog
* Sys::Hostname - determining hostname
* Sys::Hostname::Long - determining hostname
* Mail::SendEasy - sending reports by email
* Class::Std - inside/out classes builder
INCOMPATIBILITIES
Mod-perl, due to use of Class::Std. I wasn't aware of Class::Std
limitations at the time of writing Luka. There are other implementations
of inside-out classes on CPAN that should be used as replacements in of
next releases of Luka. At the moment, best candidate seems to be
Object::InsideOut.
BUGS AND LIMITATIONS
Please report any bugs or feature requests to "bug-luka@rt.cpan.org", or
through the web interface at <http://rt.cpan.org>.
TODO
mod-perl compatibility
Migration from Class::Std to Object::InsideOut, or some other
inside-out class.
severity definitions
Severity needs defining, according to appropriate existing standard.
date-time format, timezone missing
Timezone needs adding to the date-time (RFC 3339) format.
report delivery mechanism abstraction
Reporting is also event delivery, and event delivery can be done in
many ways. Currently, email is hardcoded as a delivery mechanism.
Instead, reporting delivery has to be configurable. It could be done
via dynamic loading (from a value in the config) of class
implementing desired mechanism.
reporting to syslog config setting
It is default now that Luka method "report" uses syslog for short
reporting. It should be made optional, in global, and script,
setting. Global config setting should be default; individual script
setting should override it.
event delivery on missing component section
When a section for component is missing in the config file,
exception is thrown (see DIAGNOSTICS above). Instead, event should
still be delivered, as long as relevant details about the
destination of delivery are in the global part of the Luka
configuration file.
improve documentation
Documentation needs careful re-reading and improving. Any comments
on this especially appreciated.
ACKNOWLEDGEMENTS
Ideas for underlining premises of Luka came out of discussions with Bill
Hulley.
AUTHOR
Toni Prug <toni@irational.org>
COPYRIGHT
Copyright (c) 2006. Toni Prug. All rights reserved.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
See <http://www.gnu.org/licenses/gpl.html>