FAQ
What is mod_ruby?
mod_ruby embeds the Ruby interpreter into the Apache web server, allowing Ruby CGI scripts to be executed natively. These scripts will start up much faster than without mod_ruby.
Where is it available?
It is available at the mod_ruby official site <URL:http://www.modruby.net/>.
Are there binary packages?
mod_ruby is included in Debian GNU/Linux and FreeBSD.
RPM is provided by Vine Linux.
Is there a mailing list?
<URL:mailto:modruby@modruby.net> is set up for a purpose to talk about mod_ruby (and eruby).
To subscribe this list, please send the following phrase
subscribe Your-First-Name Your-Last-Name
in the mail body (not subject) to the address <URL:mailto:modruby-ctl@modruby.net>.
Is it secure?
Yes, and No.
The default value of $SAFE is 1 on mod_ruby, so it's secure for careless programmers. For example eval(cgi["foo"][0]) causes SecurityError.
But on the other side, different scripts run using the same Ruby interpreter, so a malicious script can change the behavior of the other scripts.
Is it effective for heavy scripts?
Yes.
Someone may think fork() has little cost, relatively, for heavy scripts, so mod_ruby is not an effective way to start such scripts. But in fact it is effective, because decreasing the number of processes helps the server especially when many clients make requests simultaneously.
Does It work on Windows?
Not yet. Because I have no Windows machine (fortunately).
Can I use eRuby on mod_ruby?
Yes.
Please see Install Guide to install mod_ruby with eRuby support.
LoadModule does not work.
If ClearModuleList is in httpd.conf, Please write the following line after it.
AddModule mod_ruby.c
Why is "Content-Type" displayed on my browser?
This script does not work correctly on mod_ruby.
print "Content-Type: text/plain\r\n\r\n" print "hello world"
Because mod_ruby is compatible with NPH-CGI, so does not output the HTTP status-line. You have to output it yourself.
print "HTTP/1.1 200 OK\r\n" print "Content-Type: text/plain\r\n\r\n" print "hello world"
Or you can use cgi.rb.
require "cgi"
cgi = CGI.new
print cgi.header("type"=>"text/plain")
print "hello world"
This script is better than the previous one.
Why are changes to my library not reflected in the server?
mod_ruby scripts share the Ruby interpreter.
So a library is loaded once, require does not load the library later.
Please restart Apache like this:
# apachectl restart
Or use load instead of require for debugging.
SecurityError is raised.
On mod_ruby the default value of $SAFE is 1,
so dangerous operations with tainted string cause a SecurityError.
If it is certain that the operation is secure, use untaint.
query = CGI.new filename = query.params["filename"][0].dup filename.untaint file = open(filename)
Be careful not to make security holes!
Location header does not work.
Please specify the status line like this:
r = Apache.request r.status_line = "302 Found" r.headers_out["Location"] = "http://www.modruby.net/" r.content_type = "text/html; charset=iso-8859-1" r.send_http_header print "<html><body><h1>302 Found</h1></body></html>"
Or specify the exit status like this.
r = Apache.request r.headers_out["Location"] = "http://www.modruby.net/" exit Apache::REDIRECT
CGI::Session does not work.
On mod_ruby, CGI::Session is not closed automatically, so you should close it explicitly.
session = CGI::Session.new(...) begin ... ensure session.close end
This problem is not CGI::Session specific. You should close files etc too.
I don't know why error has occurred!
The Ruby interpreter may be in a panic because of bugs in other scripts. Please restart Apache.
Apache dies.
Ruby built by egcs-1.1.2 may cause Segmentation Fault. Please try the latest Ruby (1.6.2 or later).
Otherwise please send a bug report to the author Shugo Maeda.
apachectl restart causes memory leaks.
Currently, Ruby API does not provide a way to free memory that has
been allocated by the interpreter. So mod_ruby can't free memory on
apachectl graceful.
Please stop and start Apache for the time being.
# apachectl restart
Can't find libruby.so or liberuby.so.
libruby.so may not be in the runtime library search path.
On many Linux distributions, /usr/local/lib is not included in the runtime library search path. If you are installing mod_ruby under /usr/local, Please add the fllowing line to /etc/ld.so.conf, and run ldconfig.
/usr/local/lib
Can't override existing classes
You can't override classes in your mod_ruby scripts directly. (Instead, a new class will be defined.) Because mod_ruby scripts are loaded by Kernel#load(filename, true).
If you have to override existing classes, please do it in a library, then require it from your mod_ruby scripts.
Can't require libraries by the `loading from unsafe path' error.
Please check if there is a world writable directory in your load path ($:).
How do I keep an object instance between invocations of a page, for example, a persistent database handle?
You can keep it in a global variable. Or, you can access a class in another file, and use a class variable or class instance variable.
Example 1:
r = Apache.request
$count ||= 0
$count += 1
r.content_type = 'text/html'
r.send_http_header
r << "<html>Pid #{Process.pid}, global count #{$count}</html>"
Example 2:
require 'memory'
r = Apache.request
Memory.memory[:count] ||= 0
Memory.memory[:count] += 1
r.content_type = 'text/html'
r.send_http_header
r << "<html>Pid #{Process.pid}, memory count #{Memory.memory[:count]}</html>"
[file memory.rb]
class Memory
def self.memory
@memory ||= {}
end
end
This example demonstrates that each Apache httpd worker process keeps its own state (its own value of 'counter' in this case). If you did
$db_handle = DBI.new(...)
and had 5 worker processes, you would end up with 5 database handles, one for each worker. This is probably what you want anyway, so that each worker can perform a concurrent operation on the database.
So how can I have an object which is shared between all the worker processes?
If you do want to share data between all the worker processes, e.g. session information, one way is to keep the object in another process and access it using DRb (distributed Ruby).
Example:
# Access a DRb shared memory object [DRb client]
require 'drb'
memory = DRbObject.new(nil, 'druby://127.0.0.1:9000')
r = Apache.request
memory[:count] ||= 0
memory[:count] += 1
r.content_type = 'text/html'
r.send_http_header
r << "<html>Pid #{Process.pid}, drb count #{memory[:count]}</html>"
For this to work, you also run a standalone Ruby program containing the object and share it using DRb [a DRb server]:
#!/usr/local/bin/ruby -w
require 'drb'
memory = {}
DRb.start_service('druby://127.0.0.1:9000', memory)
DRb.thread.join
This has the big advantage that even if you stop and restart apache, the state stored in the DRb object still remains.
If you have multiple web servers in a cluster, the DRb object can be held on a different machine and accessed over the network. If you do that, you will want to make sure that the DRb object is hidden from the outside world (e.g. on a private network or protected by firewall rules) so that other people can't access it directly!
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