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 the section on "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 : "/usr/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 the section on
"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 the
section on "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 the section on "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 the section on "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 unix
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 the section on "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.
The first script to start up in a group sets the perl and
PersistentPerl parameters used from then on for all scripts in that
group. 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 user 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/).