Problem with ActiveRecord and Cerise

[Caio Chassot]

Hi all,

I'm developing a website using the cerise app server and the
activerecord ORM.

After a period of time (few hours / a day), the site stops responding.
I've tracked down the issue to activerecord. Pages that don't do a db
query via AR respond fine.

What could be hanging activerecord? A threading issue? A db connection
issue?

FYI, I'm currently calling ActiveRecord::Base.establish_connection on a
file which is required by each page handler. Is this the appropriate way
to do it?

thanks

 

[David Heinemeier Hansson]

After a period of time (few hours / a day), the site stops responding.

I've tracked down the issue to activerecord. Pages that don't do a db
query via AR respond fine.

What could be hanging activerecord? A threading issue? A db connection
issue?

Active Record is not thread safe. So if Cerise uses threads to handle
incoming connections that could indeed be your problem. The same issue
arises with WEBrick. Active Record is predominately targetted at
CGI/FCGI/mod_ruby environments where threading is not an issue.

FYI, I'm currently calling ActiveRecord::Base.establish_connection on
a file which is required by each page handler. Is this the appropriate
way to do it?

Each call to establish_connection will create a new database
connection. So if at all possible, you should try to minimize the
number of calls. In FCGI that would be to have the establish_connection
call outside of the each_cgi block. I'm not sure how it works with
Cerise.
--
David Heinemeier Hansson,
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http://www.nextangle.com/ -- Development & Consulting Services

 

[Michael Neumann]

Active Record is not thread safe. So if Cerise uses threads to handle
incoming connections that could indeed be your problem. The same issue
arises with WEBrick. Active Record is predominately targetted at
CGI/FCGI/mod_ruby environments where threading is not an issue.

Should be easy to fix by using thread-local variables instead of a class
variable:

module ActiveRecord
class Base
def self.connection
Thread.current['conn'] ||= retrieve_connection
Thread.current['conn']
end
def self.connection=(conn)
Thread.current['conn'] = conn
end
def self.connected?
!Thread.current['conn'].nil?
end
end
end


These overrides should do the trick! But haven't tested it!

Regards,

Michael

 

[Caio Chassot]

Should be easy to fix by using thread-local variables instead of a class
variable:

module ActiveRecord
class Base
def self.connection
Thread.current['conn'] ||= retrieve_connection
Thread.current['conn']
end
def self.connection=(conn)
Thread.current['conn'] = conn
end
def self.connected?
!Thread.current['conn'].nil?
end
end
end

Where retrieve_connection calls establish_connection with the approriate
parameters?

if so, it appears to have worked.

thanks.

 

[Caio Chassot]

Each call to establish_connection will create a new database connection.
So if at all possible, you should try to minimize the number of calls.
In FCGI that would be to have the establish_connection call outside of
the each_cgi block. I'm not sure how it works with Cerise.

Hi David, great library. Can't wait for the rest of rails.

The appplication persists through requests, so how about keeping the
connection in an application-wide variable?

By doing so, Michael's solution would no longer apply, so perhaps adding
a mutex to the select and execute methods of the adapter would do it?