Hey!
i need to overwrite active record find to synchronize database access
i’ve tried the following:
def self.find(*args)
begin
@@semaphore.synchronize {
super(args)
}
rescue
puts "error: "+$!
@@semaphore.unlock
end
end
def self.find_by_sql(sql)
begin
@@semaphore.synchronize {
super(sql)
}
rescue
puts "error: "+$!
@@semaphore.unlock
end
end
I always get an error:
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1227:in
find_initial': undefined methodfirst’ for nil:NilClass
(NoMethodError)
from
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:in
send' from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:infind_by_requesttype_and_requeststatus’
Obviously the dynamic finder methos like
find_by_equesttype_and_requeststatus doesn’t work.
Any clues to fix this?
Thx
On 29 May 2008, at 13:17, Christian K. wrote:
Hey!
i need to overwrite active record find to synchronize database access
You need to say super(*args). alias_method_chain is usually a more
prudent choice for this sort of stuff (and i assume you know that this
won’t accomplish anything if you’re using a pack of mongrels or
whatever - I suppose it would work if you had a single multithreaded
script, but I’m still not sure what the point would be)
Fred
Frederick C. wrote:
You need to say super(*args). alias_method_chain is usually a more
prudent choice for this sort of stuff (and i assume you know that this
won’t accomplish anything if you’re using a pack of mongrels or
whatever - I suppose it would work if you had a single multithreaded
script, but I’m still not sure what the point would be)
Fred
Problem is I’m using active_record without rails on a application that
includes a mini http server (built on top of webrick) and a background
task. Both operate on the same sqlite db. Because of concurrency issues
with sql I’m trying to synchronize access to the database.
Iven with super(*args) i still get the error:
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1227:in
find_initial': undefined methodfirst’ for nil:NilClass
(NoMethodError)
from
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:in
send' from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:infind_by_requesttype_and_requeststatus’
On 29 May 2008, at 13:34, Christian K. wrote:
Fred
Problem is I’m using active_record without rails on a application that
includes a mini http server (built on top of webrick) and a background
task. Both operate on the same sqlite db. Because of concurrency
issues
with sql I’m trying to synchronize access to the database.
Iven with super(*args) i still get the error:
Should have been obvious - it looks like you’re not returning the
right value (ie the result) from find_by_sql. Also bear in mind that
find will call find_by_sql in some cases, so make sure whatever
locking mechanism you’re using will support that. I’ve got a hint of a
doubt that by background task you mean a separate process, in which
case you’re out of luck (because each process would have its own lock).
Fred
On 29 May 2008, at 14:05, Christian K. wrote:
lock).
enough to syncronize just find_by_sql then?
Almost all. a find with an :include doesn’t in rails 2.0.2. This sort
of thing could change in the future though.
Fred
Frederick C. wrote:
Should have been obvious - it looks like you’re not returning the
right value (ie the result) from find_by_sql. Also bear in mind that
find will call find_by_sql in some cases, so make sure whatever
locking mechanism you’re using will support that. I’ve got a hint of a
doubt that by background task you mean a separate process, in which
case you’re out of luck (because each process would have its own lock).
I switched the locking mechanism to thread.exclusive, because a mutex
doesn’t work because find is calling find_by_sql. Added the returns.
def self.find(*args)
begin
#@@semaphore.synchronize {
Thread.exclusive {
#puts “find”
return super(args)
}
#}
rescue
puts "error: "+$!
# @@semaphore.unlock
end
end
def self.find_by_sql(sql)
begin
#@@semaphore.synchronize {
Thread.exclusive {
#puts "find_by_sql"
return super(sql)
}
#}
rescue
puts "error: "+$!
# @@semaphore.unlock
end
end
By background task is a second thread, not a seperate process, so the
locking mechanism should work.
Is every find call using find_by_sql to retrieve data? Would it be
enough to syncronize just find_by_sql then?
thx
FWIW you can just use super [with no args] if it’s going to use the same
arguments passed to the method. This works even if you modify the
arguments
like:
def label(object_name, method, text = nil, options = {})
text ||= method.to_s[].titleize
super
end
RSL
On Thu, May 29, 2008 at 8:26 AM, Frederick C. <