NAME
    PersistentPerl - Speed up perl scripts by running them persistently.

SYNOPSIS
     #!/usr/bin/perperl

     ### Your Script Here
     print "Content-type: text/html\n\nHello World!\n";

     ##
     ## Optionally, use the PersistentPerl module for various things
     ##

     # Create a PersistentPerl object
     use PersistentPerl;
     my $pp = PersistentPerl->new;

     # See if we are running under PersistentPerl or not.
     print "Running under perperl=", $pp->i_am_perperl ? 'yes' : 'no', "\n";

     # Register a shutdown handler
     $pp->add_shutdown_handler(sub { do something here });

     # Register a cleanup handler
     $pp->register_cleanup(sub { do something here });

     # Set/get some PersistentPerl options
     $pp->setopt('timeout', 30);
     print "maxruns=", $pp->getopt('maxruns'), "\n";

DESCRIPTION
    PersistentPerl is a way to run perl scripts persistently, which can make
    them run much more quickly. A script can be made to to run persistently by
    changing the interpreter line at the top of the script from:

        #!/usr/bin/perl

    to

        #!/usr/bin/perperl

    After the script is initially run, instead of exiting, the perl interpreter
    is kept running. During subsequent runs, this interpreter is used to handle
    new executions instead of starting a new perl interpreter each time. A very
    fast frontend program, written in C, is executed for each request. This fast
    frontend then contacts the persistent Perl process, which is usually already
    running, to do the work and return the results.

    By default each perl script runs in its own Unix process, so one perl script
    can't interfere with another. Command line options can also be used to deal
    with programs that have memory leaks or other problems that might keep them
    from otherwise running persistently.

    PersistentPerl can be used to speed up perl CGI scripts. It conforms to the
    CGI specification, and does not run perl code inside the web server. Since
    the perl interpreter runs outside the web server, it can't cause problems
    for the web server itself.

    PersistentPerl also provides an Apache module so that under the Apache web
    server, scripts can be run without the overhead of doing a fork/exec for
    each request. With this module a small amount of frontend code is run within
    the web server - the perl interpreters still run outside the server.

    SpeedyCGI and PersistentPerl are currently both names for the same code.
    SpeedyCGI was the original name, but because people weren't sure what it
    did, the name PersistentPerl was picked as an alias. At some point SpeedyCGI
    will probably be replaced by PersistentPerl, or become a sub-class of
    PersistentPerl to avoid always having two distributions.

OPTIONS
  Setting Option Values
    PersistentPerl options can be set in several ways:

    Command Line
        The perperl command line is the same as for regular perl, with the
        exception that PersistentPerl specific options can be passed in after a
        "--".

        For example the line:

                #!/usr/bin/perperl -w -- -t300

        at the top of your script will set the perl option ""-w"" and will pass
        the ""-t"" option to PersistentPerl, setting the Timeout value to 300
        seconds.

    Environment
        Environment variables can be used to pass in options. This can only be
        done before the initial execution, not from within the script itself.
        The name of the environment variable is always PERPERL_ followed by the
        option name in upper-case. For example to set the perperl Timeout
        option, use the environment variable named PERPERL_TIMEOUT.

    Module
        The PersistentPerl module provides the setopt method to set options from
        within the perl script at runtime. There is also a getopt method to
        retrieve the current options. See "METHODS" below.

    Apache
        If you are using the optional Apache module, PersistentPerl options can
        be set in the httpd.conf file. The name of the apache directive will
        always be Persistent followed by the option name. For example to set the
        Timeout option, use the apache directive PersistentTimeout.

  Context
    Not all options below are available in all contexts. The context for which
    each option is valid is listed on the "Context" line in the section below.
    There are three contexts:

    perperl
        The command-line "perperl" program, used normally with #! at the top of
        your script or from a shell prompt.

    mod_persistentperl
        The optional Apache mod_persistentperl module.

    module
        During perl execution via the PersistentPerl module's getopt/setopt
        methods.

  Options Available
    BackendProg
            Command Line    : -p<string>
            Default Value   : "/home/sam/pkg/perl-5.8.0/bin/perperl_backend"
            Context         : mod_persistentperl, perperl

            Description:

                Path to the perperl backend program.

    BufsizGet
            Command Line    : -B<number>
            Default Value   : 131072
            Context         : perperl

            Description:

                Use <number> bytes as the maximum size for the buffer that
                receives data from the perl backend.

    BufsizPost
            Command Line    : -b<number>
            Default Value   : 131072
            Context         : perperl

            Description:

                Use <number> bytes as the maximum size for the buffer that
                sends data to the perl backend.

    Group
            Command Line    : -g<string>
            Default Value   : "none"
            Context         : mod_persistentperl, perperl

            Description:

                Allow a single perl interpreter to run multiple scripts.
                All scripts that are run with the same group name and by
                the same user will be run by the same group of perl
                interpreters. If the group name is "none" then grouping is
                disabled and each interpreter will run one script.
                Different group names allow scripts to be separated into
                different groups. Name is case-sensitive, and only the
                first 12-characters are significant. Specifying an empty
                group name is the same as specifying the group name
                "default" - this allows just specifying "-g" on the command
                line to turn on grouping.

    MaxBackends
            Command Line    : -M<number>
            Default Value   : 0 (no max)
            Context         : mod_persistentperl, perperl

            Description:

                If non-zero, limits the number of perperl backends running
                for this perl script to <number>.

    MaxRuns
            Command Line    : -r<number>
            Default Value   : 500
            Context         : mod_persistentperl, module, perperl

            Description:

                Once the perl interpreter has run <number> times, re-exec
                the backend process.  Zero indicates no maximum.  This
                option is useful for processes that tend to consume
                resources over time.

    PerlArgs
            Command Line    : N/A
            Default Value   : ""
            Context         : mod_persistentperl

            Description:

                Command-line options to pass to the perl interpreter.

    Timeout
            Command Line    : -t<number>
            Default Value   : 3600 (one hour)
            Context         : mod_persistentperl, module, perperl

            Description:

                If no new requests have been received after <number>
                seconds, exit the persistent perl interpreter.  Zero
                indicates no timeout.

    TmpBase
            Command Line    : -T<string>
            Default Value   : "/tmp/perperl"
            Context         : mod_persistentperl, perperl

            Description:

                Use the given prefix for creating temporary files.  This
                must be a filename prefix, not a directory name.

    Version
            Command Line    : -v
            Context         : perperl

            Description:

                Print the PersistentPerl version and exit.

METHODS
    The following methods are available in the PersistentPerl module.

    new Create a new PersistentPerl object.

            my $pp = PersistentPerl->new;

    register_cleanup($function_ref)
        Register a function that will be called at the end of each request,
        after your script finishes running, but before STDOUT and STDERR are
        closed. Multiple functions can be added by calling the method more than
        once. At the end of the request, each function will be called in the
        order in which it was registered.

            $pp->register_cleanup(\&cleanup_func);

    add_shutdown_handler($function_ref)
        Add a function to the list of functions that will be called right before
        the perl interpreter exits. This is not at the end of each request, it
        is when the perl interpreter decides to exit completely due to a Timeout
        or reaching MaxRuns.

            $pp->add_shutdown_handler(sub {$dbh->logout});

    set_shutdown_handler($function_ref)
        Deprecated. Similar to "add_shutdown_handler", but only allows for a
        single function to be registered.

            $pp->set_shutdown_handler(sub {$dbh->logout});

    i_am_perperl
        Returns a boolean telling whether this script is running under
        PersistentPerl or not. A perl script can run under regular perl, or
        under PersistentPerl. This method allows the script to tell which
        environment it is in.

            $pp->i_am_perperl;

        To make your script as portable as possible, you can use the following
        test to make sure both the PersistentPerl module is available and you
        are running under PersistentPerl:

            if (eval {require PersistentPerl} && PersistentPerl->i_am_perperl) {
                Do something PersistentPerl specific here...

        To increase the speed of this check you can also test whether the
        following variable is defined instead of going through the object
        interface:

            $PersistentPerl::i_am_perperl

    setopt($optname, $value)
        Set one of the PersistentPerl options given in "Options Available".
        Returns the option's previous value. $optname is case-insensitive.

            $pp->setopt('TIMEOUT', 300);

    getopt($optname)
        Return the current value of one of the PersistentPerl options. $optname
        is case-insensitive.

            $pp->getopt('TIMEOUT');

    shutdown_now
        Shut down the perl interpreter right away. This function does not
        return.

            $pp->shutdown_now

    shutdown_next_time
        Shut down the perl interpreter as soon as this request is done.

            $pp->shutdown_next_time

INSTALLATION
    To install PersistentPerl you will need to either download a binary package
    for your OS, or compile PersistentPerl from source code. See "DOWNLOADING"
    for information on where to obtain the source code and binaries.

  Binary Installation
    Once you have downloaded the binary package for your OS, you'll need to
    install it using the normal package tools for your OS. The commands to do
    that are:

    Linux
         rpm -i <filename>

    Solaris
         gunzip <filename>.gz
         pkgadd -d <filename>

    BSD
         pkg_add <filename>

    If you are also installing the apache module you will have to configure
    Apache as documented in "Apache Configuration".

  Source Code Installation
    To compile PersistentPerl you will need perl 5.004 or later, and a C
    compiler, preferably the same one that your perl distribution was compiled
    with. PersistentPerl is known to work under Solaris, Redhat Linux, FreeBSD
    and OpenBSD. There may be problems with other OSes or earlier versions of
    Perl. PersistentPerl may not work with threaded perl -- as of release 2.10,
    Linux and Solaris seem to work OK with threaded perl, but FreeBSD does not.

  Standard Install
    To do a standard install from source code, execute the following:

        perl Makefile.PL
        make
        make test
        make install

    This will install the perperl and perperl_backend binaries in the same
    directory where perl was installed, and the PersistentPerl.pm module in the
    standard perl lib directory. It will also attempt to install the
    mod_persistentperl module if you have the command apxs in your path.

  Install in a Different Directory
    If you don't have permission to install into the standard perl directory, or
    if you want to install elsewhere, the easiest way is to compile and install
    your own copy of perl in another location, then use your new version of perl
    when you run "perl Makefile.PL". The PersistentPerl binaries and module will
    then be installed in the same location as the new version of perl.

    If you can't install your own perl, you can take the following steps:

    *   Edit src/optdefs and change the default value for BackendProg to the
        location where perperl_backend will be installed.

    *   Compile as above, then manually copy the perperl and perperl_backend
        binaries to where you want to install them.

    *   If you want to use the PersistentPerl module in your code (it's not
        required), you will have to use "use lib" so it can be located.

  Apache Installation
    To compile the optional apache mod_persistentperl module you must have the
    apxs command in your path. Redhat includes this command with the
    "apache-devel" RPM, though it may not work properly for installation.

    If the apache installation fails:

    *   Copy the mod_persistentperl.so from the mod_persistentperl directory, or
        from the mod_persistentperl2/.libs directory, to wherever your apache
        modules are stored (try /usr/lib/apache)

    *   Edit your httpd.conf (try /etc/httpd/conf/httpd.conf) and add the
        following lines. The path at the end of the LoadModule directive may be
        different in your installation -- look at other LoadModules to see.

            LoadModule persistentperl_module modules/mod_persistentperl.so

        If you are using Apache-1, also add:

            AddModule mod_persistentperl.c

  Apache Configuration
    Once mod_persistentperl is installed, it has to be configured to be used for
    your perl scripts. There are two methods.

    Warning! The instructions below may compromise the security of your web
    site. The security risks associated with PersistentPerl are similar to those
    of regular CGI. If you don't understand the security implications of the
    changes below then don't make them.

    1. Path Configuration
        This is similar to the way /cgi-bin works - everything under this path
        is handled by PersistentPerl. Add the following lines near the top of
        your httpd.conf - this will cause all scripts in your cgi-bin directory
        to be handled by PersistentPerl when they are accessed as
        /perperl/script-name.

            Alias /perperl/ /home/httpd/cgi-bin/
            <Location /perperl>
                SetHandler persistentperl-script
                Options ExecCGI
                allow from all
            </Location>

    2. File Extension Configuration
        This will make PersistentPerl handle all files with a certain extension,
        similar to the way .cgi files work. Add the following lines near the top
        of your httpd.conf file - this will set up the file extension ".perperl"
        to be handled by PersistentPerl.

            AddHandler persistentperl-script .perperl
            <Location />
                Options ExecCGI
            </Location>

FREQUENTLY ASKED QUESTIONS
    How does the perperl front end connect to the back end process?
        Via a Unix socket in /tmp. A queue is kept in a shared file in /tmp that
        holds an entry for each process. In that queue are the pids of the perl
        processes waiting for connections. The frontend pulls a process out of
        this queue, connects to its socket, sends over the environment and argv,
        and then uses this socket for stdin/stdout to the perl process.

    If another request comes in while PersistentPerl script is running, does the
    client have to wait or is another process started? Is there a way to set a
    limit on how many processes get started?
        If another request comes while all the perl processes are busy, then
        another perl process is started. Just like in regular perl there is
        normally no limit on how many processes get started. But, the processes
        are only started when the load is so high that they're necessary. If the
        load goes down, the processes will die off due to inactivity, unless you
        disable the timeout.

        Starting in version 1.8.3 an option was added to limit the number of
        perl backends running. See MaxBackends in "Options Available" above.

    How much of perl's state is kept when perperl starts another request? Do
    globals keep their values? Are destructors run after the request?
        Globals keep their values. Nothing is destroyed after the request.
        STDIN/STDOUT/STDERR are closed -- other files are not. %ENV and @ARGV
        are the only globals changed between requests.

    How can I make sure perperl restarts when I edit a perl library used by the
    CGI?
        Do a touch on the main cgi file that is executed. The mtime on the main
        file is checked each time the front-end runs.

    Do I need to be root to install and/or run PersistentPerl?
        No, root is not required.

    How can I determine if my perl app needs to be changed to work with perperl?
    Or is there no modification necessary?
        You may have to make modifications.

        Globals retain their values between runs, which can be good for keeping
        persistent database handles for example, or bad if your code assumes
        they're undefined.

        Also, if you create global variables with "my", you shouldn't try to
        reference those variables from within a subroutine - you should pass
        them into the subroutine instead. Or better yet just declare global
        variables with "use vars" instead of "my" to avoid the problem
        altogether.

        Here's a good explanation of the problem - it's for mod_perl, but the
        same thing applies to persistentperl:

            http://perl.apache.org/faq/mod_perl_cgi.html#Variables_retain_their_value_fro

        If all else fails you can disable persistence by setting MaxRuns to 1.
        The only benefit of this over normal perl is that perperl will
        pre-compile your script.

    How do I keep a persistent connection to a database?
        Since globals retain their values between runs, the best way to do this
        is to store the connection in a global variable, then check on each run
        to see if that variable is already defined.

        For example, if your code has an "open_db_connection" subroutine that
        returns a database connection handle, you can use the code below to keep
        a persistent connection:

            use vars qw($dbh);
            unless (defined($dbh)) {
                $dbh = &open_db_connection;
            }

        This code will store a persistent database connection handle in the
        global variable "$dbh" and only initialize it the first time the code is
        run. During subsequent runs, the existing connection is re-used.

        You may also want to check the connection each time before using it, in
        case it is not working for some reason. So, assuming you have a
        subroutine named "db_connection_ok" that returns true if the db
        connection is working, you can use code like this:

            use vars qw($dbh);
            unless (defined($dbh) && &db_connection_ok($dbh)) {
                $dbh = &open_db_connection;
            }

    Why do scripts with persistent Oracle database connections hang?
        When using an IPC connection to Oracle, an oracle process is fork'ed and
        exec'ed and keeps the stdout connection open, so that the web server
        never gets an EOF. To fix the problem, either switch to using a TCP
        connection to the database, or add the following perl code somewhere
        before the DBI->connect statement:

            use Fcntl;
            fcntl(STDOUT, F_SETFD, FD_CLOEXEC);

        This will set the close-on-exec flag on standard out so it is closed
        when oracle is exec'ed.

USING GROUPS
    The group feature in PersistentPerl can be used to help reduce the amount of
    memory used by the perl interpreters. When groups are not used (ie when
    group name is "none"), each perl script is given its own set of perl
    interpreters, separate from the perl interpreters used for other scripts. In
    PersistentPerl each perl interpreter is also a separate system process.

    When grouping is used, perl interpreters are put into a group. All perl
    interpreters in that group can run perl scripts in that same group. What
    this means is that by putting all your scripts into one group, there could
    be one perl interpreter running all the perl scripts on your system. This
    can greatly reduce your memory needs when running lots of different perl
    scripts.

    PersistentPerl group names are entities unto themselves. They are not
    associated with Unix groups, or with the Group directive in Apache. Group
    names are created by the person running PersistentPerl based on their needs.
    There are two special group names "none" and "default". All other group
    names are created by the user of PersistentPerl using the Group option
    described in "OPTIONS".

    If you want to use the maximum amount of grouping possible (ie all scripts
    in the same interpreter), then you should always use the group name
    "default". When you do this, you will get the fewest number of perl
    interpreters possible. Each perl interpreter will be able to run any of your
    perl scripts.

    Although using group "default" for all scripts results in the most efficient
    use of resources, it's not always possible or desirable to do this. You may
    want to use other group names for the following reasons:

    * To isolate misbehaving scripts, or scripts that don't work in groups.
        Some scripts cannot work in groups. When perl scripts are grouped
        together they are each given their own unique package name - they are
        not run out of the "main" package as they normally would be. So, for
        example, a script that explicitly uses "main" somewhere in its code to
        find its subroutines or variables probably won't work in groups. In this
        case, it's probably best to run such a script with group "none", so it
        is compiled and run out of package main, and always given its own
        interpreter.

        Other scripts may make changes to included packages, etc, that may break
        other scripts running in the same interpreter. In this case such scripts
        can be given their own group name (like group name "pariah") to keep
        them away from other scripts that they are incompatible with. The rest
        of your scripts can then run out of group "default". This will ensure
        that the "pariah" scripts won't run within the same interpreter as your
        other scripts.

    * To pass different perl or PersistentPerl parameters to different scripts.
        You may want to use separate groups to create separate policies for
        different scripts.

        Say you have an email application that contains ten perl scripts, and
        since the common perl code used in this application has a bad memory
        leak, you want to use a MaxRuns setting of 5 for all of these scripts.
        You then want all your other scripts to run in a separate group with a
        normal MaxRuns policy. What you can do is edit the ten email scripts,
        and at the top, put in the line:

            #!/usr/bin/perperl -- -gmail -r5

        In the rest of your perl scripts you can use:

            #!/usr/bin/perperl -- -g

        What this will do is put the ten email scripts into a group of their own
        (named "mail") and give them all the default MaxRuns value of 5. All
        other scripts will be put into the group named "default", and this group
        will have the normal MaxRuns setting.

DOWNLOADING
  Binaries
    Binaries for many OSes can be found at:

        http://daemoninc.com/PersistentPerl/download.html

  Source Code
    The standard source code distribution can be retrieved from any CPAN mirror
    or from:

        http://daemoninc.com/PersistentPerl/download.html
        http://www.cpan.org/modules/by-authors/id/H/HO/HORROCKS/

AUTHOR
        Sam Horrocks
        http://daemoninc.com
        sam@daemoninc.com

  Contributors
    A lot of people have helped out with code, patches, ideas, resources, etc.
    I'm sure I'm missing someone here - if so, please drop me an email.

    *   Gunther Birznieks

    *   Diana Eichert

    *   Takanori Kawai

    *   Robert Klep

    *   Marc Lehmann

    *   James McGregor

    *   Josh Rabinowitz

    *   Dave Parker

    *   Craig Sanders

    *   Joseph Wang

SEE ALSO
    perl(1), httpd(8), apxs(8).

MORE INFORMATION
  PersistentPerl Home Page
    http://daemoninc.com/PersistentPerl/

  Mailing List
    *   PersistentPerl users mailing list -
        persistentperl-users@lists.sourceforge.net. Archives and subscription
        information are at
        http://lists.sourceforge.net/lists/listinfo/persistentperl-users

    *   PersistentPerl announcements mailing list -
        persistentperl-announce@lists.sourceforge.net. Archives and subscription
        information are at
        http://lists.sourceforge.net/lists/listinfo/persistentperl-announce

  Bugs and Todo List
    Please report any bugs or requests for changes to the mailing list.

COPYRIGHT
    Copyright (C) 2002 Sam Horrocks

    This program is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by the Free
    Software Foundation; either version 2 of the License, or (at your option)
    any later version.

    This program is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
    more details.

    You should have received a copy of the GNU General Public License along with
    this program; if not, write to the Free Software Foundation, Inc., 59 Temple
    Place - Suite 330, Boston, MA 02111-1307, USA.

    This product includes software developed by the Apache Software Foundation
    (http://www.apache.org/).

