Locking
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Very simple plugin which adds the acquire_lock method to active record base. This is mysql only.
 
As long as a lock of a certain name is acquired no other connection on the server is able to acquire the same lock. 
This is very useful for background tasks such as billing or search server re-indexing which would cause errors when they 
would be ran from multiple machines at the same time but you still want to run them from multiple machines at the same time 
for redundancy reasons. 
 
Example
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Invoice.acquire_lock("Shopify billing") do
 
  Invoice.find_all_due.each { |invoice| invoice.collect_payment! } 
  
end
 
 
Usecase
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# save to run on several machines at the same time: 
 
 ./script/runner 'Invoice.acquire_lock("Shopify billing") {  Invoice.find_all_due.each { |invoice| invoice.collect_payment! } }'