Debugging: Rules & Tools

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

xdebug.auto_trace=1 xdebug.collect_params=4

Key Web Server PHP Script Key Debugging Client XDebug Debugging Commands

xdebug.remote_enable=1 xdebug.remote_port=9000 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

if(!is_string($i)) { throw new Xapian_Exception('Incorrect query type, expecting string or array of strings'); } $q = $this->getParser()->parse_query($i);

if(!is_string($i)) { throw new Xapian_Exception('Incorrect query type, expecting string or array of strings'); } $q = $this->getParser()->parse_query($i, FLAG_SPELLING_CORRECTION);

“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/2173

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Debugging: Rules & Tools

by Ian Barber

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