Question

Consider this begin-rescue-ensure block:

attempts=0
begin
  make_service_call()
rescue Exception
  retry unless attempts>2
  exit -1
ensure
  attemps += 1
end

If you run that code as it is, it raises an exception because there is no function called ‘make_service_call()’. So, it retries. But it would be stuck in infinite loop because the control never goes to ‘ensure’ because of the ‘retry’. Shouldn’t ‘ensure’ part of the block ensure that the code in it gets executed no matter what happens in ‘begin’ or ‘rescue’?

Of course I can increment the count in ‘begin’ – that’s not the point. I am just asking the question about ‘ensure’ to get some clarity.

Answer 1

The ensure section is executed when leaving the begin statement (by any means) but when you retry, you’re just moving around inside the statement so the ensure section will not be executed.

Try this version of your example to get a better idea of what’s going on:

attempts = 0
begin
  make_service_call()
rescue Exception
  attempts += 1
  retry unless attempts > 2
  exit -1
ensure
  puts "ensure! #{attempts}"
end