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Beyond PHP - it's not (just) about the code
 

Beyond PHP - it's not (just) about the code

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Most PHP developers focus on writing code. But creating Web applications is about much more than just writing PHP. Take a step outside the PHP cocoon and into the big PHP ecosphere to find out how ...

Most PHP developers focus on writing code. But creating Web applications is about much more than just writing PHP. Take a step outside the PHP cocoon and into the big PHP ecosphere to find out how small code changes can make a world of difference on servers and network. This talk is an eye-opener for developers who spend over 80% of their time coding, debugging and testing.

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  • 5kbit/sec or 100Mbit/sec ?
  • Let's talk about code Without : we don't exist What are most common mistakes in ecosystem Let's start with the database
  • time spent per query pattern how many queries of that query pattern
  • Get back to what I said Lots of people use ORM - easier - don't need to write queries - object-oriented but people start doing this Imagine 10000 customers → 10001 queries
  • Not best code Uses deprecated mysql extension no error handling
  • Master : 16 CPU cores 12 cores for SQL 1 core for binlog dump rest for system Slave : 16 CPU cores 1 core for slave I/O 1 core for slave SQL
  • Grouping Works fine, but : maximum size of string ? PHP = no limit MySQL = max_allowed_packet
  • All in a single commit Note : transaction has max. size Possible : combination with previous solution
  • took few moments to figure out No network monitoring → iptraf → 100Mbit/sec limit → packets dropped → connections dropped Customer : upgrade switch Us : why 100Mbit/sec ?
  • Databases → network What other network related issues ?
  • Server on which feed located : crashed Fine for few minutes (cache) 15 minutes : file_get_contents uses default_socket_timeout
  • Better, not perfect. What else is wrong ? Multiple visitors hit expiring cache → file delete → xml feed hit a lot
  • Better, not perfect. What else is wrong ? Multiple visitors hit expiring cache → file delete → xml feed hit a lot
  • How do you treat your data : - where do you get it - how long did you have to wait to get it - how is it transported - how is it processed minimize the amount of data : retrieved transported processed, sent to db and users

Beyond PHP - it's not (just) about the code Beyond PHP - it's not (just) about the code Presentation Transcript

  • Beyond PHP :Its not (just) about the code Wim Godden Cu.be Solutions
  • Who am I ? Wim Godden (@wimgtr) Founder of Cu.be Solutions (http://cu.be) Open Source developer since 1997 Developer of OpenX Zend Certified Engineer Zend Framework Certified Engineer MySQL Certified Developer Speaker at PHP and Open Source conferences
  • Cu.be Solutions ? Open source consultancy PHP-centered High-speed redundant network (BGP, OSPF, VRRP) High scalability development Nginx + extensions MySQL Cluster Projects : mostly IT & Telecom companies lots of public-facing apps/sites
  • Who are you ? Developers ? Anyone setup a MySQL master-slave ? Anyone setup a site/app on separate web and database server ? → How much traffic between them ?
  • The topic Things we take for granted Famous last words : "It should work just fine" Works fine today → might fail tomorrow Most common mistakes PHP code ↔ PHP ecosystem How-to & How-NOT-to
  • It starts with... … code ! First up : database
  • Database queries – complexity SELECT DISTINCT n.nid, n.uid, n.title, n.type, e.event_start, e.event_start AS event_start_orig, e.event_end, e.event_end AS event_end_orig, e.timezone, e.has_time, e.has_end_date, tz.offset AS offset, tz.offset_dst AS offset_dst, tz.dst_region, tz.is_dst, e.event_start - INTERVAL IF(tz.is_dst, tz.offset_dst, tz.offset) HOUR_SECOND AS event_start_utc, e.event_end - INTERVAL IF(tz.is_dst, tz.offset_dst, tz.offset) HOUR_SECOND AS event_end_utc, e.event_start - INTERVAL IF(tz.is_dst, tz.offset_dst, tz.offset) HOUR_SECOND + INTERVAL 0 SECOND AS event_start_user, e.event_end - INTERVAL IF(tz.is_dst, tz.offset_dst, tz.offset) HOUR_SECOND + INTERVAL 0 SECOND AS event_end_user, e.event_start - INTERVAL IF(tz.is_dst, tz.offset_dst, tz.offset) HOUR_SECOND + INTERVAL 0 SECOND AS event_start_site, e.event_end - INTERVAL IF(tz.is_dst, tz.offset_dst, tz.offset) HOUR_SECOND + INTERVAL 0 SECOND AS event_end_site, tz.name as timezone_name FROM node n INNER JOIN event e ON n.nid = e.nid INNER JOIN event_timezones tz ON tz.timezone = e.timezone INNER JOIN node_access na ON na.nid = n.nid LEFT JOIN domain_access da ON n.nid = da.nid LEFT JOIN node i18n ON n.tnid > 0 AND n.tnid = i18n.tnid AND i18n.language = en WHERE (na.grant_view >= 1 AND ((na.gid = 0 AND na.realm = all))) AND ((da.realm = "domain_id" AND da.gid = 4) OR (da.realm = "domain_site" AND da.gid = 0)) AND (n.language =en OR n.language = OR n.language IS NULL OR n.language = is AND i18n.nid IS NULL) AND ( n.status = 1 AND ((e.event_start >= 2010-01-31 00:00:00 AND e.event_start <= 2010-03-01 23:59:59) OR (e.event_end >= 2010-01-31 00:00:00 AND e.event_end <= 2010-03-01 23:59:59) OR (e.event_start <= 2010-01-31 00:00:00 AND e.event_end >= 2010-03-01 23:59:59)) ) GROUP BY n.nid HAVING (event_start >= 2010-02-01 00:00:00 AND event_start <= 2010-02-28 23:59:59) OR (event_end >= 2010-02-01 00:00:00 AND event_end <= 2010-02-28 23:59:59) OR (event_start <= 2010-02-01 00:00:00 AND event_end >= 2010-02-28 23:59:59) ORDER BY event_start ASC;
  • Database - indexing select id from stock where status = 2 order by qty → aggregate index on (status, qty) select id from stock where status > 2 order by qty → aggregate index on (status, qty) ? → No : range selection stops use of aggregate index → separate index on status and qty
  • Database - indexing Indexes make database faster → Lets index everything ! → DONT : Insert/update/delete → Index modification Each query → evaluation of all indexes "Relational schema design is based on data but index design is based on queries" (Bill Karwin, Percona)
  • Databases – detecting problematic queries Slow query log → SET GLOBAL slow_query_log = ON; Queries not using indexes → In my.cnf/my.ini : log_queries_not_using_indexes General query log → SET GLOBAL general_log = ON; → Turn it off quickly ! Percona Toolkit (Maatkit) pt-query-digest
  • Databases - pt-query-digest# Profile# Rank Query ID Response time Calls R/Call Apdx V/M Item# ==== ================== ================ ===== ======= ==== ===== ==========# 1 0x543FB322AE4330FF 16526.2542 62.0% 1208 13.6806 1.00 0.00 SELECT output_option# 2 0xE78FEA32E3AA3221 0.8312 10.3% 6412 0.0001 1.00 0.00 SELECT poller_output poller_item# 3 0x211901BF2E1C351E 0.6811 8.4% 6416 0.0001 1.00 0.00 SELECT poller_time# 4 0xA766EE8F7AB39063 0.2805 3.5% 149 0.0019 1.00 0.00 SELECT wp_terms wp_term_taxonomy wp_term_relationships# 5 0xA3EEB63EFBA42E9B 0.1999 2.5% 51 0.0039 1.00 0.00 SELECT UNION wp_pp_daily_summary wp_pp_hourly_summary# 6 0x94350EA2AB8AAC34 0.1956 2.4% 89 0.0022 1.00 0.01 UPDATE wp_options# MISC 0xMISC 0.8137 10.0% 3853 0.0002 NS 0.0 <147 ITEMS>
  • Databases - pt-query-digest # Query 2: 0.26 QPS, 0.00x concurrency, ID 0x92F3B1B361FB0E5B at byte 14081299 # This item is included in the report because it matches --limit. # Scores: Apdex = 1.00 [1.0], V/M = 0.00 # Query_time sparkline: | _^ | # Time range: 2011-12-28 18:42:47 to 19:03:10 # Attribute pct total min max avg 95% stddev median # ============ === ======= ======= ======= ======= ======= ======= ======= # Count 1 312 # Exec time 50 4s 5ms 25ms 13ms 20ms 4ms 12ms # Lock time 3 32ms 43us 163us 103us 131us 19us 98us # Rows sent 59 62.41k 203 231 204.82 202.40 3.99 202.40 # Rows examine 13 73.63k 238 296 241.67 246.02 10.15 234.30 # Rows affecte 0 0 0 0 0 0 0 0 # Rows read 59 62.41k 203 231 204.82 202.40 3.99 202.40 # Bytes sent 53 24.85M 46.52k 84.36k 81.56k 83.83k 7.31k 79.83k # Merge passes 0 0 0 0 0 0 0 0 # Tmp tables 0 0 0 0 0 0 0 0 # Tmp disk tbl 0 0 0 0 0 0 0 0 # Tmp tbl size 0 0 0 0 0 0 0 0 # Query size 0 21.63k 71 71 71 71 0 71 # InnoDB: # IO r bytes 0 0 0 0 0 0 0 0 # IO r ops 0 0 0 0 0 0 0 0 # IO r wait 0 0 0 0 0 0 0 0 # pages distin 40 11.77k 34 44 38.62 38.53 1.87 38.53 # queue wait 0 0 0 0 0 0 0 0 # rec lock wai 0 0 0 0 0 0 0 0 # Boolean: # Full scan 100% yes, 0% no # String: # Databases wp_blog_one (264/84%), wp_blog_tw… (36/11%)... 1 more # Hosts # InnoDB trxID 86B40B (1/0%), 86B430 (1/0%), 86B44A (1/0%)... 309 more # Last errno 0 # Users wp_blog_one (264/84%), wp_blog_two (36/11%)... 1 more # Query_time distribution # 1us # 10us # 100us # 1ms # 10ms ################################################################ # 100ms # 1s # 10s+ # Tables # SHOW TABLE STATUS FROM `wp_blog_one ` LIKE wp_optionsG # SHOW CREATE TABLE `wp_blog_one `.`wp_options`G # EXPLAIN /*!50100 PARTITIONS*/ SELECT option_name, option_value FROM wp_options WHERE autoload = yesG
  • Databases – pt-query-digest – Digest UI
  • Databases – next step : explain explain <query> "How will MySQL execute the query"
  • Databases – next step : explain +----+-------------+-----------+------+---------------+------+---------+------+--------+-------------+ | id | select_type | TABLE | TYPE | possible_keys | KEY | key_len | REF | ROWS | Extra | +----+-------------+-----------+------+---------------+------+---------+------+--------+-------------+ | 1 | SIMPLE | employees | ALL | NULL | NULL | NULL | NULL | 299809 | USING WHERE | +----+-------------+-----------+------+---------------+------+---------+------+--------+-------------+ +----+-------------+------------+-------+-------------------------------+---------+---------+-------+------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+-------+-------------------------------+---------+---------+-------+------+-------+ | 1 | SIMPLE | itdevice | const | PRIMARY,fk_device_devicetype1 | PRIMARY | 4 | const | 1 | | | 1 | SIMPLE | devicetype | const | PRIMARY | PRIMARY | 4 | const | 1 | | +----+-------------+------------+-------+-------------------------------+---------+---------+-------+------+-------+
  • Databases – next step : explain explain <query> "How will MySQL execute the query" Shows : Indexes available Indexes used (do you see one ?) Number of rows scanned Type of lookup system, const and ref = good ALL = bad Extra info Using index = good Using filesort = usually bad Using where = bad
  • Databases – when to use / not to use Good at : Fetching data Storing data Searching through data Bad at : select `someField` from `bigTable` where crc32(`field`) = "something" → full table scan
  • For / foreach $customers = CustomerQuery::create() ->filterByState(SC) ->find(); foreach ($customers as $customer) { $contacts = ContactsQuery::create() ->filterByCustomerid($customer->getId()) ->find(); foreach ($contacts as $contact) { doSomestuffWith($contact); } }
  • Joins $contacts = mysql_query(" select contacts.* from customer join contact on contact.customerid = customer.id where state = SC "); while ($contact = mysql_fetch_array($contacts)) { doSomeStuffWith($contact); } or the ORM equivalent
  • Better... 10001 → 1 query Sadly : people still produce code with query loops Usually : Growth not anticipated Internal app → Public app
  • The origins of this talk Customers : Projects we built Projects we didnt build, but got pulled into Fixes Changes Infrastructure migration 15 years of how to cause mayhem with a few lines of code
  • Client X Jobs search site Monitor job views : Daily hits Weekly hits Monthly hits Which user saw which job
  • Client X Originally : when user viewed job details Now : when job is in search result Search for php → 50 jobs = 50 jobs to be updated → 50 updates for shown_today → 50 updates for shown_week → 50 updates for shown_month → 50 inserts for shown_user
  • Client X : the codeforeach ($jobs as $job) { $db->query(" $db->query(" insert into shown_month( insert into shown_today( jobId, jobId, number number ) values( ) values( " . $job[id] . ", " . $job[id] . ", 1 1 ) ) on duplicate key on duplicate key update update number = number + 1 number = number + 1 "); "); $db->query(" $db->query(" insert into shown_user( insert into shown_week( jobId, jobId, userId, number when ) values( ) values ( " . $job[id] . ", " . $job[id] . ", 1 " . $user[id] . ", ) now() on duplicate key ) update "); number = number + 1 } ");
  • Client X : the graph
  • Client X : the numbers 600-1000 updates/sec (peaks up to 1600) 400-1000 updates/sec (peaks up to 2600) 16 core machine
  • Client X : panic ! Mail : "MySQL slave is more than 5 minutes behind master" We set it up → who did they blame ? Wait a second !
  • Client X : whats causing those peaks ?
  • Client X : possible cause ? Code changes ? → According to developers : none Action : turn on general log, analyze with pt-query-digest → 50+-fold increase in queries → Developers : Oops we did make a change After 3 days : 2,5 days behind Every hour : 50 min extra lag
  • Client X : But why is the slave lagging ? File : File : master-bin-xxxx.log Slave I/O thread master-bin-xxxx.log p Sl um av g d ad th e S re Q n lo e ad L Bi thr Master Slave
  • Client X : Master
  • Client X : Slave
  • Client X : fix ?foreach ($jobs as $job) { $db->query(" $db->query(" insert into shown_month( insert into shown_today( jobId, jobId, number number ) values( ) values( " . $job[id] . ", " . $job[id] . ", 1 1 ) ) on duplicate key on duplicate key update update number = number + 1 number = number + 1 "); "); $db->query(" $db->query(" insert into shown_user( insert into shown_week( jobId, jobId, userId, number when ) values( ) values ( " . $job[id] . ", " . $job[id] . ", 1 " . $user[id] . ", ) now() on duplicate key ) update "); number = number + 1 } ");
  • Client X : the code change $todayQuery = " insert into shown_today( jobId, number ) values "; foreach ($jobs as $job) { $todayQuery .= "(" . $job[id] . ", 1),"; } $todayQuery = substr($todayQuery, -1); $todayQuery .= " ) on duplicate key update number = number + 1 "; $db->query($todayQuery);Result : insert into shown_today values (5, 1), (8, 1), (12, 1), (18, 1), ... Careful : max_allowed_packet !
  • Client X : the chosen solution$db->autocommit(false); $db->query("foreach ($jobs as $job) { insert into shown_month( $db->query(" jobId, insert into shown_today( number jobId, ) values( number " . $job[id] . ", ) values( 1 " . $job[id] . ", ) 1 on duplicate key ) update on duplicate key number = number + 1 update "); number = number + 1 $db->query(" "); insert into shown_user( $db->query(" jobId, insert into shown_week( userId, jobId, when number ) values ( ) values( " . $job[id] . ", " . $job[id] . ", " . $user[id] . ", 1 now() ) ) on duplicate key "); update } number = number + 1 $db->commit(); ");
  • Client X : conclusion For loops are bad (we already knew that) Add master/slave and it gets much worse Use transactions : it will provide huge performance increase Result : slave caught up 5 days later
  • Database → Network Customer Y Top 10 site in Belgium Growing rapidly At peak traffic : Unexplicable latency on database Load on webservers : minimal Load on database servers : acceptable
  • Client Y : the network
  • Client Y : the network 60GB 700GB 700GB
  • Client Y : network overload Cause : Drupal hooks → retrieving data that was not needed Only load data you actually need Dont know at the start ? → Use lazy loading Caching : Same story Memcached/Redis are fast But : data still needs to cross the network
  • Network trouble : more than just traffic Customer Z 150.000 visits/day News ticker : XML feed from other site (owned by same customer) Cached for 15 min
  • Customer Z – fetching the feed if (filectime(APP_DIR . /tmp/ScrambledSiteName.xml) < time() - 900) { unlink(APP_DIR . /tmp/ScrambledSiteName.xml); file_put_contents( APP_DIR . /tmp/ScrambledSiteName.xml, file_get_contents(http://www.scrambledsitename.be/xml/feed.xml) ); } $xmlfeed = ParseXmlFeed(APP_DIR . /tmp/ScrambledSiteName.xml); Whats wrong with this code ?
  • Customer Z – no feed without the source Feed source
  • Customer Z – no feed without the source Feed source
  • Customer Z : timeout default_socket_timeout : 60 sec by default Each visitor : 60 sec wait time People keep hitting refresh → more load More active connections → more load Apache hits maximum connections → entire site down
  • Customer Z : timeout fix$context = stream_context_create( array( http => array( timeout => 5 ) ));if (filectime(APP_DIR . /tmp/ScrambledSiteName.xml) < time() - 900) { unlink(APP_DIR . /tmp/ScrambledSiteName.xml); file_put_contents( APP_DIR . /tmp/ScrambledSiteName.xml, file_get_contents(http://www.scrambledsitename.be/xml/feed.xml, false, $context) );}$xmlfeed = ParseXmlFeed(APP_DIR . /tmp/ScrambledSiteName.xml);
  • Customer Z : dont delete from cache$context = stream_context_create( array( http => array( timeout => 5 ) ));if (filectime(APP_DIR . /tmp/ScrambledSiteName.xml) < time() - 900) { unlink(APP_DIR . /tmp/ScrambledSiteName.xml); file_put_contents( APP_DIR . /tmp/ScrambledSiteName.xml, file_get_contents(http://www.scrambledsitename.be/xml/feed.xml, false, $context) );}$xmlfeed = ParseXmlFeed(APP_DIR . /tmp/ScrambledSiteName.xml);
  • Network resources Use timeouts for all : fopen curl SOAP … Data source trusted ? → setup a webservice → let them push updates when their feed changes → less load on data source → no timeout issues Add logging → early detection
  • Logging Logging = good Logging in PHP using fopen → bad idea : locking issues → Use file_put_contents($filename, $data, FILE_APPEND) For Firefox : FirePHP (add-on for Firebug) Debug logging = bad on production Watch your logs ! Dont log on slow disks → I/O bottlenecks
  • File system : I/O bottlenecks Causes : Excessive writes (database updates, logfiles, swapping, …) Excessive reads (non-indexed database queries, swapping, small file system cache, …) How to detect ? top iostat See iowait ? Stop worrying about php, fix the I/O problem !
  • File system Worst of all : NFS PHP files → lstat calls Templates → same Sessions → locking issues → corrupt data → store sessions in database, Memcached, Redis, ...
  • Much more than code XML feed Network User Webserver DB server
  • Questions ?
  • Questions ?
  • Contact Twitter @wimgtr Web http://techblog.wimgodden.be Slides http://www.slideshare.net/wimg E-mail wim.godden@cu.be Please... Rate my talk : http://spkr8.com/t/21141
  • Thanks ! Please...Rate my talk : http://spkr8.com/t/21141