http://api.rubyonrails.org/classes/ActiveRecord/Locking/Pessimistic.html
On May 4, 7:27 am, Amit Rawal <[email protected]> wrote: > Hello, > > Here is the logic that I am trying to achieve. I have a User Model and > the business rule is that user can accept maximum 5 friends requests. > > for this I have an accept method in User Model which looks similar to > below code snippet > > def accept(friend) > raise ArgumentError if self.friends.count >= MAX_FRIENDS_ALLOWED > ... > ... > #code to add friend to friends list > end > As you can see that I basically query for count of friends for a user > and if the count is greater then or equal to MAX_FRIENDS_ALLOWED the > friend accept request should not go through. > > From the UI perspective I have a link_to_remote, "Accept" link that > calls an action which calls the User Model's "accept" method. Basically > UI looks like > > FRIEND NAME | Action > --------------------------- > AAAAA | Accept > BBBBB | Accept > CCCCC | Accept > DDDDD | Accept > EEEEE | Accept > FFFFF | Accept > > Now from UI I try to accept multiple friends requests by clicking on > "Accept" link (which makes an ajax request) quickly. > > When I run this in under normal development environment (running single > mongrel), everything works fine i.e. the validation put in User Model's > "accept" method works. > > After that I configured 4 mongrel in a cluster and ran it behind > lighttpd and then ran in to trouble. > > I guess the problem here is that since I run cluster of mongrels each > mongrel executes the request in separate process because of which before > the a friend is accepted, another process executes "self.friends.count" > and it will not reflect the updated count. I tried to enclose the above > statements in Activerecord transaction, but it did not work and the > reason I think is that transaction is per-database connection and each > process will spawn a separate connection. > > Please suggest any workarounds or probably solution to this issue. > -- > Posted viahttp://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
