再帰処理で再試行してみる。データ取得は他の関数にやらせるといいかも。

retry.rb

a = [nil, nil, nil, 'hoge']
b = Array.new a #set same data

def get ar, rc
  return "Couldn't get data in retry count" if rc == 0
  puts "Trying get data..."; sleep 3
  dat = ar.shift
  return "Found!: \"#{dat}\"" unless dat.nil?
  puts 'data not found. retrying...'; sleep 1
  get ar, rc - 1
end

puts get a, 3
puts '--------------'
puts get b, 4

# Out put:
=begin
Trying get data...
data not found. retrying...
Trying get data...
data not found. retrying...
Trying get data...
data not found. retrying...
Couldn't get data in retry count
--------------
Trying get data...
data not found. retrying...
Trying get data...
data not found. retrying...
Trying get data...
data not found. retrying...
Trying get data...
Found!: "hoge"
=end