Pro PHP Application Performance Tuning PHP Web Projects for Maximum Performance phần 6 potx

ab results for Listing 5–7 code Adding the full logic to the sample application we’ll be using reduces the total number of requests per second to 73.46, and a request is satisfied in 68.

$statement = "SELECT num FROM chapter5 ORDER BY num DESC";

$results = mysql_query($statement, $dbHandler)

or die ('Could not run SQL: '.mysql_error($dbHandler));

Figure 5–6 ab results for Listing 5–7 code

Adding the full logic to the sample application we’ll be using reduces the total

number of requests per second to 73.46, and a request is satisfied in 68.067ms Not a very ideal set of numbers—that’s a 65 percent decrease in total requests per second and a 184 percent increase to satisfy a single request Let’s go ahead and use APC to improve these numbers

APC Caching

In Chapter 4, we implemented APC to exclusively cache PHP Opcode In this chapter, we will use APC to store information To do so, we’re going to focus on a subset of internal

PHP APC methods shown in Table 5–1 Before we begin, make sure you have the APC

PHP extension fully installed The complete steps to install APC are shown in Chapter 4

Table 5–1 APC Functions

Function Parameters Description

apc_add() apc_add(String key, Mixed

var, int Expiration Time)

Adds content into cache using specific key if key does not already exist

apc_fetch() apc_fetch(Mixed key) Fetches content of a specific key within cache Returns

false if key not found

acp_store() apc_store(String key, Mixed

var, int Expiration Time)

Stores a value in cache using a specific key Will replace value if key exists

Function Parameters Description

apc_exists() apc_exists(mixed keys) Checks if the key is present in cache Returns true if key

exists, false otherwise

apc_delete() apc_delete(String key) Removes a specific key from cache Returns true if

successful, false otherwise

■ Note Additional APC functions can be found at www.php.net/apc

The functions outlined in the table allow us to add data into shared memory, fetch data from shared memory using a specific key, check to determine if the key is present, and finally remove content from cache that is associated to a specific key

Adding Data to Cache

Using some of the functions outlined in Table 5–1, we’re going to create a small page counter, shown in Listing 5–8, before applying it to our database-driven web application

Listing 5–8 Page Counter: Adding Content to APC Cache

Using Listing 5–8 as only an example to introduce us to using APC data caching, the code contains a working page counter that keeps a running count of users visiting this

PHP script within two minutes of the initial visit The page counter begins by calling

apc_fetch() to both fetch and check if the specified key, myCounter, exists within cache If the key does not exist, the $counter variable is set equal to 1, and a new key, myCounter, is inserted into shared memory, APC cache On the other hand, if the key is found, it simply fetches the data currently in cache, increments the value by 1, and uses apc_store() to

update the data stored within the myCounter key Finally, we present the visitor count to the user

In this example, we also make use of the third parameter, apc_add() By specifying an integer value of 120 seconds (2 minutes), we request the cache information to remain

valid for 2 minutes Once the data has expired, the cache key will update during a request Let’s apply caching using APC to our sample database-driven application

Benchmarking APC

Using the APC functions you just learned, we are going to apply them to our

database-driven application by placing the functions where our bottlenecks are within the code,

connecting, and fetching data from the database Update the code as shown in Listing 5–9

Listing 5–9 APC Caching Applied to Listing 5–7 Code

$dbHandler = mysql_connect($host, $username, $password, $dbName)

or die('Connection error: '.mysql_error($dbHandler));

//Connect to db

mysql_select_db($dbName, $dbHandler)

or die ('Could not connect to db: '.mysql_error($dbHandlder));

//Fetch the records from the Database

$statement = "SELECT num FROM chapter5 ORDER BY num DESC";

$results = mysql_query($statement, $dbHandler)

or die ('Could not run SQL: '.mysql_error($dbHandler));

The code has only minor updates shown in bold Like the code shown in Listing 5–7,

we have added the apc_add() as well as the apc_fetch() functions Using the code, let’s use ab once again and determine what APC caching offers in terms of performance The results for our ab simulation are shown in Figure 5–7

Figure 5–7 ab results for APC cache enabled

Figure 5–7 displays our results for the ab run Comparing the results shown in Figure 5–7 with those shown in Figure 5–6, we see an improvement in the number of requests

the server can satisfy and a decrease in the speed in which the web server can satisfy a

single request The number of users the server can now satisfy increased by 72.51 percent, while the total time to satisfy a single request decreased by 42 percent Using APC

improved the performance of our application

The drop in time and the increase in the number of users now supported can be

attributed to a fetch from memory rather than the recurring three-step process of

opening the database connection, executing the SQL statement, and fetching the data By fetching the data, your users no longer have to execute these steps until after two

minutes, in this example To further improve the performance of our script, we can also cache the HTML that is generated, allowing the complete table to be fetched from

memory

APC is not the only tool out there that can help in caching data Memcached is

another tool that can be used

Memcached

Unlike other caching tools covered in this chapter and in Chapter 4, Memcached was the original caching solution for PHP Memcached was originally developed by Brad

Fitzpatrick for the web application Livejournal in 2003 and then found great backing

within the open source community It now has wide use in major web applications such

as Wikipedia, Flickr, Twitter, and YouTube, just to name a few

In the following sections, we will cover the install process, review the PHP

Memcached functions, and fine-tune our setup to get the most from it

Installing Memcached

Memcached’s stable release is currently at version 1.4.5 and can be found and

downloaded from the web site www.memcached.org There are two methods to installMemcached You can either download the source tgz file from the listed web site, or use

a distribution port using apt-get or yum

If you’re on a system that has apt-get installed, run the command apt-get installphp5–memcached

The command will install all necessary dependencies and packages for Memcached.Restart your web server and verify PHP successfully loaded the Memcached extensions bycreating a phpinfo() PHP script, and load the file using your web browser If everythingwas installed correctly, you should see the Memcached PHP settings as shown in Figure5–8

Figure 5–8 Memcached info within phpinfo page

The alternative method to install Memcached is by using the source Download thesource and execute the commands shown in Listing 5–10 within a terminal

Listing 5–10 Installing Memcached from Source

./configure

make

make install

Once Memcached has been installed, restart the web server and load a phpinfo script

to make sure all was installed correctly You should see the Memcached settings as shown

in Figure 5–8

Starting Memcached Server

Turn on Memcached by specifying the amount of memory to allocate to it as well as itsport to run on By default Memcached listens on port 11211, but you can change thisbehavior using the –p parameters Execute the command /usr/bin/memcached –m 512 –p

11211 to begin Memcached

Using Memcached with PHP

PHP has bundled a list of Memcached methods within the PHP Memcached class We will focus on the subset of methods listed in Table 5–2 to get you familiar with the tool The

methods shown allow you to add content to the cache, fetch content from the cache,

update content within cache, flush all the content, and delete a specific item from cache

Table 5–2 Memcached Methods

Method Parameters Description

Memcached::add() add(String key, mixed Value, int

Expiration Time in seconds)

Adds a new key/value into cache Will fail if key present

Memcached::get() get(String key, Callback function,

float cas_token)

Get content from cache for a specific key

Returns false if key is not present

memcached::set() set(String key, Mixed value, int

Expiration Time in seconds)

Set the content for a specific key Unlike

add(), it will not fail if key is present

memcached::flush() flush(int time) Removes all keys and content from cache

memcached::delete() delete(String key, int Time in

seconds)

Removes a specific key from cache If time is present, any attempt to add the key into cache will be ignored until time expires

■ Note The complete list of Memcached available methods can be found within the PHP documentation at www.php.net/memcached

Connecting to Memcached Server

Before we save data into our new Memcached server, we need to open a connection to it, much like opening a connection to a database or creating a handler to a file Listing 5–11 contains a simple PHP 5 code example that connects to the Memcached server running locally

Listing 5–11 Connecting to Memcached Server

Adding Data into Cache

As in the previous APC section, you're going to use the visitors counter code shown in Listing 5–8 as an introduction to using the Memcached functions The updated visitor counter code is shown in Listing 5–12

Listing 5–12 Using Memcached for a Page Counter

$memCached->set('myCounter', $counter, 120);

}

echo "Your visitor number: ".$counter;

The logic is identical to Listing 5–8: we check if the cache has a value for myCounter

using an if-else statement If the cache does contain a value, we increment the value and store the new value into cache Otherwise we initialize the content to store and place the value into a new key within cache

While using Memcached, we begin by creating the Memcached object, adding a

Memcached server using the method addServer(), identify if there is data within shared memory using the Memcached method get(), and if there is no data present, we initialize the data using the $counter variable and add the data into a new key, myCounter, along

with the initial value of 1, using Memcached::add()

$dbHandler = mysql_connect($host, $username, $password, $dbName)

or die('Connection error: '.mysql_error($dbHandler));

//Connect to db

mysql_select_db($dbName, $dbHandler)

or die ('Could not connect to db: '.mysql_error($dbHandlder));

//Fetch the records from the Database

$statement = "SELECT num FROM chapter5 ORDER BY num DESC";

$results = mysql_query($statement, $dbHandler)

or die ('Could not run SQL: '.mysql_error($dbHandler));

Figure 5–9 ab results for Listing 5–13

Summary

This wraps the focus on the PHP code itself As you'd expect from reading Chapter 2,

optimization isn’t just about PHP—it’s about all the layers PHP runs on To push our app

to the best performance possible, we started with the tool sets to measure, followed by

the client-side JavaScript and CSS optimization, and then used caching for PHP With

Chapter 4 and Chapter 5 introducing and applying a caching solution for not only our

Opcode but also large sections of data that is required for our application to run, we have covered the foundation of what caching is and what it can do within our PHP application

In Chapter 5, we focused on APC as well as Memcached You learned the terminology behind caching, used the built-in PHP functions to store, retrieve, and clear cache from APC, installed and used Memcached, and most importantly created small experiments to test how well APC as well as Memcached increased performance In the remaining

chapters, we’ll focus on the software our application runs on

security of your installation and track that as new exploits are discovered, then Apache is probably the best bet

Availability of Engineers with Detailed Knowledge Is Important to You

Nginx and lighttpd, while mainstream, are not as well known in the community as the

venerable Apache server If you rely on being able to locate and hire engineers with level web server skills, then Apache is again probably the best bet

guru-Your Site Is Predominantly Static Content

If you are running a photo or video hosting site, then the enhanced static object serving performance that lighttpd or Nginx can bring to the table is probably a good reason to

take a long, hard look at these newer alternatives

You Are Hosting in a Managed Service

Many managed hosting services are traditional in the components that they provide for hosting applications Before committing yourself to a design that relies on servers other than Apache, check with your hoster to see if it is supported

You Are Using Unusual PHP Extensions

Most PHP extension writers assume that PHP will be running on Apache with mod_php

Testing of extensions under FCGI, which is the mechanism used by lighttpd and Nginx to host the PHP interpreter, is often not done Before committing to using these alternative web server packages, check that all the PHP extensions your application requires work

correctly in FCGI mode

Usage Figures for Web Servers

One of the factors that should be considered when choosing a web server package is its

popularity If a web server is popular, it means there are a lot of people using it, shaking out bugs, providing support services, etc Web servers that are lower in the popularity

stakes may not have the same exposure as their more popular brethren (see Table 6–1)

Table 6–1 Web Server Package Popularity (Source: Netcraft 2010)

Vendor Product Web Sites

Web Server Request Handling

Web servers have to perform a set of well-defined processes on an incoming request asspecified by the HTTP specifications In order to produce the required output, this

sequence of events is known as the “Request Processing Pipeline,” as it describes asequence or pipeline of actions that need to be performed to handle a request

Although the details of how this occurs in each web server package vary greatly, theyall generally follow the same pattern

• Request Listener: This component is responsible for picking up an

inbound network connection from the browser, and reading therequest from the socket

• Request Parsing: Takes the request and parses it into a data structure

that can be easily interpreted by the rest of the web servercomponents; most web servers expose this parsed data as a “RequestObject” to applications running on it It is also responsible for

decoding things such as the cookie jar and making it available as adictionary of values

• Input Filter: This component is responsible for any transformations

that need to be applied to the request If the web server is capable ofperforming any URL rewriting, then it is typically done at this stage