cache

Cache may refer to: read more at WikiPedia

  • Resources such as JavaScript and CSS files can be compressed before being sent to the browser, improving network efficiencies and application load time in certain case. If you are not using Apache with mod_deflate or nginx in front of your web application, you may need to implement resources compression yourself….

    Wait! don’t start writing your own filter to compress files like CSS, html, txt, javascript it is way more difficult than you think to properly handle http response headers and do proper handling of mime type and caching. In one sentence don’t start reinventing the wheel: use ehcache for example.

    Ehcache is an open source, standards-based cache used to boost performance, offload the database and simplify scalability. Ehcache is robust, proven and full-featured and this has made it the most widely-used Java-based cache. It can scale from in-process with one or more nodes through to a mixed in-process/out-of-process configuration with terabyte-sized caches. For applications needing a coherent distributed cache, Ehcache uses the open source Terracotta Sever Array.

    in the pom.xml of your project add the following dependency to ehcache-web

    <dependency>
        <groupId>net.sf.ehcache</groupId>
        <artifactId>ehcache-web</artifactId>
        <version>2.0.4</version>
    </dependency>

    in your web.xml, add a filter and configure it properly

    <filter>
     <filter-name>CompressionFilter</filter-name>
     <filter-class>net.sf.ehcache.constructs.web.filter.GzipFilter</filter-class>
    </filter>
    <filter-mapping>
     <filter-name>CompressionFilter</filter-name>
     <url-pattern>*.css</url-pattern>
    </filter-mapping>
    <filter-mapping>
     <filter-name>CompressionFilter</filter-name>
     <url-pattern>*.html</url-pattern>
    </filter-mapping>
    <filter-mapping>
     <filter-name>CompressionFilter</filter-name>
     <url-pattern>*.js</url-pattern>
    </filter-mapping>
    <filter-mapping>
     <filter-name>CompressionFilter</filter-name>
     <url-pattern>/*</url-pattern>
    </filter-mapping>

    Read more at EhCache Web Caching page.

    As a bonus, I provide you also below the configuration for the famous challenger HTTP server nginx

     ##
     # Gzip Settings
     ##
     gzip  on;
     gzip_http_version 1.1;
     gzip_vary on;
     gzip_comp_level 6;
     gzip_proxied any;
     gzip_types text/plain text/css application/json application/x-javascript \
    text/xml application/xml application/xml+rss text/javascript \
    application/javascript text/x-js; gzip_buffers 16 8k; gzip_disable "MSIE [1-6]\.(?!.*SV1)";

    &160;

    or for the number one HTTP server Apache using mod deflate /etc/apache2/conf.d/deflate.conf

    <Location />
    # Insert filter
    SetOutputFilter DEFLATE
    
    AddOutputFilterByType DEFLATE text/plain
    AddOutputFilterByType DEFLATE text/xml
    AddOutputFilterByType DEFLATE application/xhtml+xml
    AddOutputFilterByType DEFLATE text/css
    AddOutputFilterByType DEFLATE application/xml
    AddOutputFilterByType DEFLATE image/svg+xml
    AddOutputFilterByType DEFLATE application/rss+xml
    AddOutputFilterByType DEFLATE application/atom_xml
    AddOutputFilterByType DEFLATE application/x-javascript
    AddOutputFilterByType DEFLATE text/html
    
    # Netscape 4.x has some problems...
    BrowserMatch ^Mozilla/4 gzip-only-text/html
    
    # Netscape 4.06-4.08 have some more problems
    BrowserMatch ^Mozilla/4\.0[678] no-gzip
    
    # MSIE masquerades as Netscape, but it is fine
    BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
    # Don't compress images
    SetEnvIfNoCase Request_URI \
    \.(?:gif|jpe?g|png)$ no-gzip dont-vary
    
    # Make sure proxies don't deliver the wrong content
    Header append Vary User-Agent env=!dont-vary
    </Location>
  • Impact of Zend Optimizer on PHP Performance

    The Zend Optimizer FAQ answers the question "Why use the Zend Optimizer?" with this statement: "The standard Zend run-time compiler used by PHP is indeed extremely fast, generating code that is usually 2 to 10 times faster. But an application that uses the Zend Optimizer typically executes another 40% to 100% faster."

    Read the results of the load test HERE.

  • The Alternative PHP Cache (APC) is a free and open opcode cache for PHP. It was conceived of to provide a free, open, and robust framework for caching and optimizing PHP intermediate code. from http://nl2.php.net/apc

    Links:
    Unpack your distribution file. You will have downloaded a file named something like apc_x.y.tar.gz. Unzip this file with a command like
    # wget http://pecl.php.net/get/APC-3.0.14.tgz
    # gunzip apc_x.y.tar.gz

    Next you have to untar it with
    #  tar xvf apc_x.y.tar

    This will create an apc_x.y directory. cd into this new directory:
    # cd apc_x.y

    phpize is a script that should have been installed with PHP, and is normally located in /usr/local/php/binassuming you installed PHP in /usr/local/php. (If you do not have the phpize script, you must reinstall PHP and be sure not to disable PEAR.).

    Locate phpize:
    # find / -name phpize

    mine is in
     /etc/alternatives/phpize
    yours may be in /usr/local/php/bin/phpize

    Run the phpize command:
    #  /usr/local/php/bin/phpize

    Its output should resemble this:
            Configuring for:
              PHP Api Version:   20020918
              Zend Module Api No:   20020429
              Zend Extension Api No:   20021010


    phpize should create a configure script in the current directory. If you get errors instead, you might be missing some required development tools, such as autoconf or libtool. You can try downloading the latest versions of those tools and running phpize again.

    Run the configure script.

    phpize creates a configure script. The only option you need to specify is the location of your php-config script.

    find location of php-config
    # find / -name php-config
    then
    # ./configure --enable-apc --enable-apc-mmap --with-apxs --with-php-config=/etc/alternatives/php-config

    php-config should be located in the same directory as phpize.
    If you prefer to use mmap instead of the default IPC shared memory support,  add --enable-apc-mmap to your configure line.

        If you prefer to use sysv IPC semaphores over the safer fcntl() locks, add --enable-sem to your configure line.  If you don't have a problem
        with your server segaulting, or any other unnatural accumulation of semaphores on your system, the semaphore based locking is slightly faster.

    Compile and install the files.
    Simply type:
    # make install
    Installing shared extensions:     /usr/lib/php5/extensions/


    Suggested Configuration (in your php.ini file)

      extension=apc.so
      apc.enabled=1
      apc.shm_segments=1
      apc.shm_size=128
      apc.ttl=7200
      apc.user_ttl=7200
      apc.num_files_hint=1024
      apc.mmap_file_mask=/tmp/apc.XXXXXX
      apc.enable_cli=1



    Although the default APC settings are fine for many installations, serious
    users should consider tuning the following parameters:

        OPTION                  DESCRIPTION
        ------------------      --------------------------------------------------
        apc.enabled             This can be set to 0 to disable APC. This is
                                primarily useful when APC is statically compiled
                                into PHP, since there is no other way to disable
                                it (when compiled as a DSO, the zend_extension
                                line can just be commented-out).
                                (Default: 1)

        apc.shm_segments        The number of shared memory segments to allocate
                                for the compiler cache. If APC is running out of
                                shared memory but you have already set
                                apc.shm_size as high as your system allows, you
                                can try raising this value.  Setting this to a
                                value other than 1 has no effect in mmap mode
                                since mmap'ed shm segments don't have size limits.
                                (Default: 1)

        apc.shm_size            The size of each shared memory segment in MB.
                                By default, some systems (including most BSD
                                variants) have very low limits on the size of a
                                shared memory segment.
                                (Default: 30)

        apc.optimization        This option has been deprecated.
                                (Default: 0)

        apc.num_files_hint      A "hint" about the number of distinct source files
                                that will be included or requested on your web
                                server. Set to zero or omit if you're not sure;
                                this setting is mainly useful for sites that have
                                many thousands of source files.
                                (Default: 1000)

        apc.user_entries_hint   Just like num_files_hint, a "hint" about the number
                                of distinct user cache variables to store.
                                Set to zero or omit if you're not sure;
                                (Default: 4096)

        apc.ttl                 The number of seconds a cache entry is allowed to
                                idle in a slot in case this cache entry slot is
                                needed by another entry.  Leaving this at zero
                                means that your cache could potentially fill up
                                with stale entries while newer entries won't be
                                cached.
                                (Default: 0)

        apc.user_ttl            The number of seconds a user cache entry is allowed
                                to idle in a slot in case this cache entry slot is
                                needed by another entry.  Leaving this at zero
                                means that your cache could potentially fill up
                                with stale entries while newer entries won't be
                                cached.
                                (Default: 0)


        apc.gc_ttl              The number of seconds that a cache entry may
                                remain on the garbage-collection list. This value
                                provides a failsafe in the event that a server
                                process dies while executing a cached source file;
                                if that source file is modified, the memory
                                allocated for the old version will not be
                                reclaimed until this TTL reached. Set to zero to
                                disable this feature.
                                (Default: 3600)

     apc.cache_by_default    On by default, but can be set to off and used in
                                conjunction with positive apc.filters so that files
                                are only cached if matched by a positive filter.
                                (Default: On)

        apc.filters             A comma-separated list of POSIX extended regular
                                expressions. If any pattern matches the source
                                filename, the file will not be cached. Note that
                                the filename used for matching is the one passed
                                to include/require, not the absolute path.  If the
                                first character of the expression is a + then the
                                expression will be additive in the sense that any
                                files matched by the expression will be cached, and
                                if the first character is a - then anything matched
                                will not be cached.  The - case is the default, so
                                it can be left off.
                                (Default: "")

        apc.mmap_file_mask      If compiled with MMAP support by using --enable-mmap
                                this is the mktemp-style file_mask to pass to the
                                mmap module for determing whether your mmap'ed memory
                                region is going to be file-backed or shared memory
                                backed.  For straight file-backed mmap, set it to
                                something like /tmp/apc.XXXXXX (exactly 6 X's).
                                To use POSIX-style shm_open/mmap put a ".shm"
                                somewhere in your mask.  eg.  "/apc.shm.XXXXXX"
                                You can also set it to "/dev/zero" to use your
                                kernel's /dev/zero interface to anonymous mmap'ed
                                memory.  Leaving it undefined will force an
                                anonymous mmap.
                                (Default: "")

        apc.slam_defense        ** DEPRECATED - Use apc.write_lock instead **
                                On very busy servers whenever you start the server or
                                modify files you can create a race of many processes
                                all trying to cache the same file at the same time.
                                This option sets the percentage of processes that will
                                skip trying to cache an uncached file.  Or think of it
                                as the probability of a single process to skip caching.
                                For example, setting this to 75 would mean that there is
                                a 75% chance that the process will not cache an uncached
                                file.  So the higher the setting the greater the defense
                                against cache slams.  Setting this to 0 disables this
                                feature.
                                (Default: 0)

        apc.file_update_protection
                                When you modify a file on a live web server you really
                                should do so in an atomic manner.  That is, write to a
                                temporary file and rename (mv) the file into its permanent
                                position when it is ready.  Many text editors, cp, tar and
                                other such programs don't do this.  This means that there
                                is a chance that a file is accessed (and cached) while it
                                is still being written to.  This file_update_protection
                                setting puts a delay on caching brand new files.  The
                                default is 2 seconds which means that if the modification
                                timestamp (mtime) on a file shows that it is less than 2
                                seconds old when it is accessed, it will not be cached.
                                The unfortunate person who accessed this half-written file
                                will still see weirdness, but at least it won't persist.
                                If you are certain you always atomically update your files
                                by using something like rsync which does this correctly, you
                                can turn this protection off by setting it to 0.  If you
                                have a system that is flooded with io causing some update
                                procedure to take longer than 2 seconds, you may want to
                                increase this a bit.
                                (Default: 2)

        apc.enable_cli          Mostly for testing and debugging.  Setting this enables APC
                                for the CLI version of PHP.  Normally you wouldn't want to
                                create, populate and tear down the APC cache on every CLI
                                request, but for various test scenarios it is handy to be
                                able to enable APC for the CLI version of APC easily.
                                (Default: 0)

        apc.max_file_size       Prevents large files from being cached.
                                (Default: 1M)

        apc.stat                Whether to stat the main script file and the fullpath
                                includes.  If you turn this off you will need to restart
                                                                                            

     apc.write_lock          On busy servers when you first start up the server, or when
                                many files are modified, you can end up with all your processes
                                trying to compile and cache the same files.  With write_lock
                                enabled, only one process at a time will try to compile an
                                uncached script while the other processes will run uncached
                                instead of sitting around waiting on a lock.
                                (Default: 1)

        apc.report_autofilter   Logs any scripts that were automatically excluded from being
                                cached due to early/late binding issues.
                                (Default: 0)

        apc.rfc1867             RFC1867 File Upload Progress hook handler is only available
                                if you compiled APC against PHP 5.2.0 or later.  When enabled
                                any file uploads which includes a field called
                                APC_UPLOAD_PROGRESS before the file field in an upload form
                                will cause APC to automatically create an upload_<key>
                                user cache entry where <key> is the value of the
                                APC_UPLOAD_PROGRESS form entry.

                                Note that the file upload tracking is not threadsafe at this
                                point, so new uploads that happen while a previous one is
                                still going will disable the tracking for the previous.
                                (Default: 0)

        apc.localcache          This enables a lock-free local process shadow-cache which
                                reduces lock contention when the cache is being written to.
                                (Default: 0)

        apc.localcache.size     The size of the local process shadow-cache, should be set to
                                a sufficently large value, approximately half of num_files_hint.
                                (Default: 512)

        apc.include_once_override
                                Optimize include_once and require_once calls and avoid the
                                expensive system calls used.
                                (Default: 0)