Thread programming ref reshers - ruby style

A quick link pointer - differences b/w ruby mutex and monitors

Some quick tips:
Monitors are re-entrant - meaning you can nest calls to methods that synchronize access to some data
Mutex is not re-entrant

Ruby blocks - explicit vs implicit arguments

I wanted to pass an implicit block argument to a call to super. Looks like the most efficient way is to use

def on_ready
unless paused?
super { yield }
end
end

-----------------------

From http://www.ruby-forum.com/topic/71221


require 'benchmark'

def outer11(&bl)
inner1(&bl)
end

def outer12(&bl)
inner2(&bl)
end

def outer21
inner1 {yield}
end

def outer22
inner2 {yield}
end

def inner1(&bl)
bl.call
end

def inner2
yield
end

n = 100000

Benchmark.bmbm(10) do |rpt|
rpt.report("outer11") do
n.times {outer11{}}
end

rpt.report("outer12") do
n.times {outer12{}}
end

rpt.report("outer21") do
n.times {outer21{}}
end

rpt.report("outer22") do
n.times {outer22{}}
end
end

__END__

Output:

Rehearsal ---------------------------------------------
outer11 0.890000 0.010000 0.900000 ( 0.894500)
outer12 0.370000 0.000000 0.370000 ( 0.364880)
outer21 0.770000 0.000000 0.770000 ( 0.776638)
outer22 0.170000 0.000000 0.170000 ( 0.163393)
------------------------------------ total: 2.210000sec

user system total real
outer11 0.490000 0.000000 0.490000 ( 0.491969)
outer12 0.400000 0.000000 0.400000 ( 0.396264)
outer21 0.760000 0.000000 0.760000 ( 0.764508)
outer22 0.160000 0.000000 0.160000 ( 0.161982)

CookierStore::CookieOverflow

/!\ FAILSAFE /!\  Sun Mar 22 23:51:44 -0700 2009
  Status: 500 Internal Server Error
  ActionController::Session::CookieStore::CookieOverflow

This error is typically due to the user trying to store > 4K of data in the session.

Another source of error is if you try to store $! in flash[:error]

begin
  ....
rescue 
  flash[:error] = $!
end

This tries to store the ruby exception object in the flash (which in turn is stored in the cookie) and you will start getting the cookie overflow errors.

The solution is simple

begin
  ....
rescue 
  flash[:error] = $!.to_s
end

-

ORA-12516: TNS:listener could not find available handler with matching protocol stack

We use Oracle Database 10g Express Edition Release 10.2.0.1.0 for our RoR development and were hitting the TNS:listener error all the time. This made concurrent development a real pain and we couldn't leave staging servers and sqldeveloper sessions up.

Google searches turned up really scant information - mainly advices to increase the PROECESSES limit. I am not a DBA, so wasn't sure what needed to be done.
In any case, the following solution worked like a charm and I hope others who have this issue find this post useful.

source /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/bin/oracle_env.csh
setenv ORACLE_SID XE

And then execute the following steps to increase the number processes and sessions:
1) Connect to the database using the sys or system user:
sqlplus SYSTEM/<syspwd>@//<dbhost>/xe
2) To confirm the PROCESSES and SESSIONS values, run the following script:
 sql> col name format A30
 Sql> col value format A30
 sql> select name, value from v$parameter where name in ('processes','sessions');
3) SQL> alter system set processes=300 scope=spfile;
4) SQL> alter system set sessions=300 scope=spfile;
5) Bounce the database to reflect the changes
6) To confirm new values run the script (2).