DEBUGGING
R U L E S A N D TO O L S
ian barber - http://phpir.com - @ianbarber

I did X
I wanted Y
Instead I got Z

http://www.debuggingrules.com

RULE 1
UNDERSTAND
THE SYSTEM

Bug
Wiki Tracker Frame
work
RTFM PHP
Doc
php.net

$field = $document->getField($fieldName);
if ($field->storeTermVector) {
/**
* @todo term vector storing support
*/
require_once
'Zend/Search/Lucene/Exception.php';
throw new Zend_Search_Lucene_Exception
('Store term vector functionality is not
supported yet.');
}

Komodo
Eclipse Zend
Studio
TOOLS
PHP Net
Storm Text Beans
Mate

RULE 2
MAKE IT
FAIL

Recreate And
Automate
PHP Unit
SimpleTest
Selenium
PHP Slim
JMeter
Ab

Time
Load Timing
User
Server
CONTROL
Env
VARIABLES
Request
Client DB
State
Session

[root@localhost ~]# pear channel-discover pear.phpunit.de
[root@localhost ~]# pear install phpunit/PHPUnit
class Test_User extends
PHPUnit_Framework_TestCase {
public function testUpdate() {
$r = ("a", "b");
try {
$u = User::fetch($this->newName);
$result = $u->update($r);
} catch (Id_Exception $e) {
$this->fail($e->getMessage());
}
$this->assertEquals($r, $u->getRoles());
}
}

http://seleniumhq.org/

class Example extends
PHPUnit_Extensions_SeleniumTestCase {
protected function setUp() {
$this->setBrowser("*chrome");
$this->setBrowserUrl("http://general.dev/");
}
public function testMyTestCase() {
$this->open("/");
$this->select("locale", "label=de");
$this->waitForPageToLoad("30000");
$this->assertTrue($this->isTextPresent(
"Datenbank-Einrichtung"));
}
}

http://jakarta.apache.org/jmeter/

RULE 3
QUIT THINKING
AND LOOK

if($this->hasRoles) {
$this->deleteRoles();
}
try {
foreach($submittedRoles as $role) {
$this->addRole($role);
}
} catch(Identity_Exception $e) {
$this->log->warn('Role add failed.');
throw new Service_Exception_BadRequest(
'Cannot add user role');
}

Instrumentation:
Inspect or Report

Xdebug
http://www.xdebug.org
[root@localhost ~]# pecl install xdebug
zend_extension=/usr/lib64/php/modules/xdebug.so

xdebug.profiler_enable=1
xdebug.profiler_output_dir=/tmp

Web Server
PHP Script
Debugging Client XDebug
Debugging Commands

xdebug.remote_enable=1
xdebug.remote_port=9000
xdebug.remote_mode=req
xdebug.remote_host=192.168.192.1 # xdebug.remote_connect_back=1

[root@localhost ~]# lsof -p 4365
COMMAND USER FD TYPE DEVICE NAME
httpd apache mem REG 253,0 /lib64/libssl.so.0.9.8e
httpd apache mem REG 253,0 /usr/lib64/php/modules/xdebug.so
httpd apache mem REG 253,0 /usr/lib64/libsqlite3.so.0.8.6
[root@localhost ~]# strace -cp 4365
Process 6910 attached - interrupt to quit
Process 6910 detached
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- -------------
36.91 0.037307 466 80 getdents
30.07 0.030393 950 32 7 access
17.04 0.017224 154 112 10 open
5.08 0.005136 12 444 9 lstat
3.87 0.003910 18 213 1 read
3.04 0.003071 29 107 close
2.57 0.002598 1299 2 writev
0.78 0.000785 1 631 stat

[root@localhost ~]# strace -Tp 4365
Process 6910 attached - interrupt to quit
epoll_wait(16, {{EPOLLIN, {u32=31389672, u64=47128707528680}}},
2, 10000) = 1 <6.926140>
accept(4, {sa_family=AF_INET6, sin6_port=htons(64930), inet_pton
(AF_INET6, "::ffff:192.168.192.1", &sin6_addr),
sin6_flowinfo=0, sin6_scope_id=0}, [47128676139036]) = 17
<0.000094>
fcntl(17, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000035>
read(17,
"POST / HTTP/1.1rnHost: general.d"...,
8000) = 522 <0.000044>
stat("/mnt/hgfs/habari/htdocs/", {st_mode=S_IFDIR|0755,
st_size=408, ...}) = 0 <0.000527>
open("/mnt/hgfs/habari/htdocs/.htaccess",
O_RDONLY) = 18 <0.000457>
fcntl(17, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000037>

[root@localhost ~]# strace -Tp 4365
Process 6910 attached - interrupt to quit
epoll_wait(16, {{EPOLLIN, {u32=31389672, u64=47128707528680}}},
2, 10000) = 1 <6.926140>
accept(4, {sa_family=AF_INET6, sin6_port=htons(64930), inet_pton
(AF_INET6, "::ffff:192.168.192.1", &sin6_addr),
sin6_flowinfo=0, sin6_scope_id=0}, [47128676139036]) = 17
<0.000094>
fcntl(17, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000035>
read(17,
"POST / HTTP/1.1rnHost: general.d"...,
8000) = 522 <0.000044>
stat("/mnt/hgfs/habari/htdocs/", {st_mode=S_IFDIR|0755,
st_size=408, ...}) = 0 <0.000527>
open("/mnt/hgfs/habari/htdocs/.htaccess",
O_RDONLY) = 18 <0.000457>

Zend Drupal
Log syslog
sfLogger
Kohana
Log
error_log("Message for the PHP log")
error_log("Log to email", 1, "me@foo.com");
error_log("Log to a file",3, "/tmp/m.log");
error_log("Message for the SAPI log", 4);

MQ Syslog File
LOGGING
SYSTEM
Gearman Database Pipe

FirePHP

[root@localhost ~]# pear channel-discover pear.firephp.org
[root@localhost ~]# pear install firephp/FirePHPCore
require_once('FirePHPCore/FirePHP.class.php');
ob_start();
$firephp = FirePHP::getInstance(true);
doStuff($firephp);
$firephp->warn('Done Stuff');
$firephp->error('An error!');
$firephp->log($_GET);
ob_end_flush();
function doStuff($firephp) {
$firephp->trace('Stuff Backtrace');
echo "This page intentionally blank";
}

RULE 4
DIVIDE AND
CONQUER

<?xml version="1.0" encoding="UTF-8"?>
<phpunit bootstrap="./TestHelper.php"
colors="true">
<testsuite name="Commonlib Tests">
<directory>./library/Cl/</directory>
<directory>./library/Sso/</directory>
</testsuite>
<filter>
<whitelist>
<directory suffix=".php">../Sso/</directory>
<directory suffix=".php">../Cl/</directory>
</whitelist>
</filter>
</phpunit>

Folder Root
CL SSO
Auth Client Model User
Adapter Plugin Exception Abstract
SSO SFDC Gearman

<?php
$worker = new GearmanWorker();
$worker->addServer();
$worker->addFunction(
"allow_access", "allowAccess");
$worker->addFunction(
"deny_access", "denyAccess");
while ($worker->work());

Git Bisect
git bisect start
git bisect bad
git bisect good <known good rev>
git bisect ?
git bisect reset

good bad
1
Request View
2
Front 3
Controller Plugin
Input Model
Filter
Controller

Firewall
Cache
Web Server
Database

Tamper
Data
Curl
Firewall
Wireshark
Cache Netcat
Web Server
MySQL
Proxy Xdebug
Database

Tamper Data
https://addons.mozilla.org/firefox/addon/966

Wireshark
http://www.wireshark.org/

[root@localhost ~]# { echo -ne "HTTP/1.0 200 OKrn
rn"; cat test.html; } | nc -l 8080
GET / HTTP/1.1
User-Agent: curl/7.19.7 (i386-apple-darwin10.0.0)
libcurl/7.19.7 OpenSSL/0.9.8l zlib/1.2.3
Host: general.dev:8080
Accept: */*
[root@localhost ~]# curl http://general.dev:8080 -v
* About to connect() to general.dev port 8080 (#0)
* Trying 192.168.192.129... connected
* Connected to general.dev (192.168.192.129) port
8080 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.19.7 (i386-apple-darwin10.0.0)
libcurl/7.19.7 OpenSSL/0.9.8l zlib/1.2.3
> Host: general.dev:8080

local log_file = 'mysql.log'
local fh = io.open(log_file, "a+")
function read_query( packet )
if string.byte(packet) == proxy.COM_QUERY
then
local query = string.sub(packet, 2)
fh:write( string.format("%sn",query))
fh:flush()
end
end
MySQL Proxy

RULE 5
CHANGE ONE
THING AT
A TIME

[root@localhost ~]#: svn st
M index.php
[root@localhost ~]#: git stash save
Saved working directory and index state WIP
on master: 0e22fdd Initial checkin
HEAD is now at 0e22fdd Initial checkin
[root@localhost ~]#: git status
# On branch master
nothing to commit (working directory clean)
Source Control

[root@localhost ~]#: svn log .
-------------------------------------------
r4341 | rickc | 2010-09-24 03:01 | 3 lines
Don't test if Post::tags is empty before
getting tags. There may be a performance
hit for this. It can be dealt with if it is
noticable. Fixes ticket #1235. Props to ilo
for the patch.
Note that Post still needs to be updated to
use real Tags, not an array of slug/label
pairs as the tags member.
--------------------------------------------
Source Control

Known Good
[root@localhost ~]# diff -yw web.conf web2.conf
<VirtualHost *:80> <VirtualHost *:80>
ServerAdmin root@e.com ServerAdmin root@e.com
DocumentRoot /www/htdocs | DocumentRoot /www/hdocs
ServerName general.dev ServerName general.dev
ErrorLog logs/error_log ErrorLog logs/error_log
</VirtualHost> </VirtualHost>

RULE 6
KEEP AN
AUDIT TRAIL

Hot Key Log
http://www.blacktree.com/
http://do.davebsd.com/
https://launchpad.net/mb
http://simplenoteapp.com/

Backpack Journal
http://backpackit.com/

[root@localhost htdocs]# history 20
365 ls /mnt/hgfs/habari/
366 ls
367 vi /etc/httpd/conf.d/web.conf
368 setenforce 0
369 /etc/init.d/httpd restart
370 vi /var/log/httpd/error_log
371 cd /mnt/hgfs/habari/
372 ls
373 cd htdocs/
374 ls
375 cd scripts/
376 ls
377 cd ..
378 ls
379 vi /etc/php.ini

RULE 7
CHECK THE
PLUG

Sources of Plugs
[root@localhost ~]# apachectl -M
Loaded Modules:
core_module (static)
mpm_prefork_module (static)
http_module (static)
so_module (static)
[root@localhost ~]# whoami
auth_basic_module (shared)
root
auth_digest_module (shared)
[root@localhost ~]# ifconfig
authn_file_module (shared)
eth0 Link encap:Ethernet HWad
authn_alias_module (shared)
authn_anon_module inet addr:192.168.192.129
(shared)
inet6 addr: fe80::20c:29ff:
authn_dbm_module (shared)

RULE 8
GET A FRESH
VIEW

“Grovelling is not
a substitute for
doing your
homework”
- ESR
http://www.catb.org/esr/faqs/smart-questions.html

RULE 9
IF YOU DIDN’T
FIX IT -
IT AIN’T FIXED

Five Whys
The page is blank: Why?
There is a fatal error: Why?
No mb_check_encoding(): Why?
mbstring is not installed: Why?
It isn’t part of the build: Why?
It was setup for another project.

The Rules
1. Understand The System
2. Make It Fail
3. Quit Thinking And Look
4. Divide And Conquer
5. Change One Thing At A Time
6. Keep An Audit Trail
7. Check The Plug
8. Get A Fresh View
9. If You Didn’t Fix It, It Ain’t Fixed

Questions
?

Image Credits
When men were men and wore white coats - by Jitze
http://www.flickr.com/photos/jitze1942/4292084185/
Vacuum Tube Etch-A-Sketch - by Jurvetson
http://www.flickr.com/photos/jurvetson/197768962/
Classic - by Oskay
http://www.flickr.com/photos/oskay/1364147095
Firmware Bug - by Oskay
http://www.flickr.com/photos/oskay/1364148351
Ready to hop - by Oskay
http://www.flickr.com/photos/oskay/1364153441/
Albino - by Oskay
http://www.flickr.com/photos/oskay/1364143833
Coming Through! - by Oskay
http://www.flickr.com/photos/oskay/1364147807
Tux the Pinguin - by Patrick van der Velden
From the photographer’s private collection

THANKANDTOOLS
DEBUGGING: RULES
YOU
http://joind.in/3393