Turbocharging PHP Apps with Zend Server Code Tracing and Caching

Turbocharging PHP
Applications With Zend
Server.

Eric Ritchie (eric@zend.com)

© All rights reserved. Zend Technologies, Inc.

Eric Ritchie bids you welcome!
• Senior Technical Consultant and Trainer
at Zend Technologies

• Zend Framework and PHP 5.3 ZCE

• Eighteen years of system administration experience

• Twelve years of PHP (3,4 & 5) and five years Zend
Framework development experience

• Hobbies: Sampling good wines/whiskies
(gifts welcome)


Agenda

• Defining the problem
• The sharpest tool in the shed… Code Tracing
• Laziness is good (at least for web servers):
Using caching to avoid work
• If we must work, then procrastinate: Use the Job Queue
• Taking the heat off the disk: Ways to reduce disk I/O


What we will not cover (probably)

• Database optimization > caching
• Web service optimization
• Varnish and reverse proxying in general
• CDNs (Content Delivery Networks)
• Caching technology comparisons
• Operating system level optimizations
• JavaScript performance in general
• Network Traffic Analysis


Defining the problem
Why is it that we always discover that we have performance
problems AFTER we go live?


The evolution of an organic website
• A new website is born...

Internet

LAMP Server


...too much of a good thing?
• the smoke begins...

Internet

LAMP Server


First job: Bottleneck identification

• Many possible tools:
 Zend Server Event Monitoring

 Profiling

 microtime()

 Slow query logs

• One Swiss army knife:
 Zend Server Code Tracing


Zend Code Tracing
A black box for your PHP code


Zend Code Tracing: Main view


Zend Code Tracing: Statistics view


Zend Code Tracing: How to store a trace?

• Best way (in most cases)
 … Use a web browser

 Very quick and easy, but obviously not so good for POST requests

 Also, we may not be allowed!


Zend Code Tracing: How to store a trace?
• The official way
 … Use event monitoring

 Works for all requests where an event is generated
 Great for catching random problems
 Custom events allow for „programmatic“ generation of traces


Caching
Reducing the work load of our application architecture


Zend Page Cache

• Dynamic content is expensive, so don’t regenerate
 Low impact, since no code changes may be required

 Complete request cached, so a hit is like a static request

 Multiple copies of pages can be maintained

 Controlled by flexable and comprehensive rules

• Sadly, nothing comes for free
 Page design can render page caching useless

 Highly dynamic content cannot be reasonably cached

 Problems with stale content


Zend Page Caching: Custom content


Zend Page Cache: Configuration


Data caching

• Protects the data layer:
 Helps prevent repetitive DB/web service calls

 Far easier than scaling the database

• But...
 Requires code changes

 Custom data is also problematic

 Risk of delivering stale content

 De-caching can bring down the data source


One common architecture
• Network data cache
e.g. Memcache

Internet DB Server(s)

LB

Cache
Server
Web Farm


Network data cache

• Some advantages
 Only one cache to update/invalidate

 Most effective way of protecting the data source

• Many disadvantages...
 Single point of failure (or uncertainty when in distributed mode)

 Limits scalability

 Performance bottleneck

 Slower


A different approach
• Shared memory cache Cache
e.g. Zend Data Cache

Cache

Internet DB Server(s)

X
LB Cache

Cache
Server
Web Farm


Zend Data Cache: A shared memory cache

• Many advantages
 Completely scalable (copy/paste architecture)

 No single point of failure

 Does not require TCP/IP

 Very fast

• Some disadvantages...
 Not the path of least resistance

 More work for the data source or the developer

 Your colleagues may laugh at you (but they would be wrong)


Zend Data Cache: Usage

• Inserting into the cache
 $res = zend_shm_cache_store($key, $value, $ttl)

 $res = zend_disk_cache_store($key, $value, $ttl)

• Reading from the cache
 $value = zend_shm_cache_fetch($key)

 $value = zend_disk_cache_fetch($key)

• In all cases the key can contain a namespace to allow
grouping of data, e.g. namespace::key


Zend Data Cache: Usage

• Deleting from the cache
 $res = zend_shm_cache_delete($key)

 $res = zend_disk_cache_delete($key)

• Wiping the cache
 $res = zend_shm_cache_clear()

 $res = zend_disk_cache_clear()


Shared memory caching

• Taming the disadvantages
 True, we need to work a little, but...
• We can use Zend Server‘s Job Queue to perform remote
cache maintenance
• We can get a list of active servers from the Web API
provided by Zend Server
• Really, we don‘t have to code much ourselves


Remote de-caching
• With Zend Server‘s Job Queue

• ...and the job itself


Shared memory cache on steroids

• Don‘t decache, update
 Regenerate the data and insert into the cache

 At a minimum do this for all components of the index page

 Reduces data source load


Zend Job Queue
Why do now what you can do a little later?
Or, genius is being calm on the surface while being calculating in
the background. Your application should do just that.
Or, your server‘s marketing department.


Zend Job Queue

• Doesn’t make PHP faster, but makes it look that way
 Break slow tasks out of the user workflow

 Offload the heavy lifting to a background server.

 Delay expensive tasks to off peak hours

 Helps to prevent repetitve work reducing overall load

• Possible to create jobs which depend on other jobs, run
regularly and have set priorites
• Hooks into Zend Server‘s Event Monitoring component
 Jobs can feedback status information

 Problems appear in the central Zend Server event list


Zend Job Queue: Typical example


Zend Job Queue: Basic use

• Would be hard to make it easier…

• We can also pass information to our job...


Zend Job Queue: Basic use

• Possible to name our jobs and set an earliest start time…

• Once sheduled, it is possible to check up on jobs


Zend Job Queue: Querying jobs

• Finding out the status of our job using the job id

 Find out if the job is still queued, running, completed or failed

 When finished we get a copy of the script‘s output


Zend Job Queue: Querying jobs

• Searching for jobs

 Search for an existing queued job of the same type

 Useful for avoiding repetitive work

 Returns the number of matching jobs along with job details


Optimization vs. Complexity


Optimization vs. Complexity

• With every optimization complexity increaces
 Who else dropped into the caching pitfall?

• First: implement functionality
• System performing well?
• If not, check why
• Get rid of bottlenecks


Reducing Disk I/O
The only component of a web server slower than the disk
subsystem is the guy you ask to set it up.


Reducing disk I/O

• Use an opcode cache e.g. Zend Optimizer+
 Avoids the need to open PHP files and compile the contents for
every request.
 Compiled „opcodes“ are instead held in shared memory for later
reuse.
 Particularly important for framework based projects where tens
of files may be needed to answer one request.
 Also saves some compiler time, but disk I/O savings are usually far
more significant.
 Most obvious benefit for scripts with short run times or running on
loaded servers.


Reducing disk I/O

• Store static files elsewhere
• Do not cache to the file system
• Must have local storage? ...Use a ramdisk
• Reduce PHP/Apache logging to minimal levels
 E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR

• Don‘t forget the Zend Server logs!
 Search for log_verbosity_level in the configuration


File system concerns

• EXT3 – The default problem
 For a web server ReiserFS can be 20x (or more) faster, really!

 Even XFS is 2.5x faster

 If you must use EXT3/4 then throw memory at the server

• My NFS/Samba server is fast... Honest!
 Even „fast“ NFS servers have terrible performance under load

 Older implementations cannot use buffer cache

 Poor scalability

• Distributed file systems
 Extremely poor scalability


PHP uses your network

• PHP communicates with network services like
 Databases (ex: MySQL, Oracle)

 Caching systems (ex: Memcache, Redis ..)

 Job Queue Systems (ex: Zend Job Queue, RabbitMQ )

 Session Clustering Daemon (ex: Zend Session Clustering)

• If one of these services overloads the network then all
other suffer from slowdown
 Network congestion

 Insufficient bandwidth

 High latency


So long...

• …and thanks for all the fish.


Turbocharging PHP Apps with Zend Server Code Tracing and Caching

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