First comments for Retries and RobustServer.

This commit is contained in:
Denis Knauf 2010-03-11 11:32:27 +01:00
parent c992701299
commit 899a1dd399

View file

@ -4,6 +4,7 @@ def Signal.signame s
when String then s
when Symbol then s.to_s
when Fixnum then list.invert[s]
else raise ArgumentError, "String, Symbol or Fixnum expected, not #{s.class}"
end
end
@ -12,6 +13,7 @@ def Signal.sig s
when Fixnum then s
when String then list[s]
when Symbol then list[s.to_s]
else raise ArgumentError, "String, Symbol or Fixnum expected, not #{s.class}"
end
end
@ -25,25 +27,58 @@ def Signal.[] s
when String then list[s]
when Symbol then list[s.to_s]
when Fixnum then list.invert[s]
else raise ArgumentError
else raise ArgumentError, "String, Symbol or Fixnum expected, not #{s.class}"
end
end
# Counts retries ot something. If the retries are to often in a short time,
# you shouldn't retry again.
#
# Example:
# retries = Retry.new 5, 1
# begin
# array_of_ints_and_some_strings.each do |i|
# puts 2*i
# end
# rescue TypeError
# retries.retry? and retry
# raise $!
# end
#
# Retry.new( 10, 30).run( ConnectionLost) do
# try_to_connect_to_db
# try_query
# end
class Retries
attr_accessor :max, :range
attr_reader :count, :last
# max: How many retries in range-time are allowed maximal.
# range: In which time-range are these retries are allowed
def initialize max = nil, range = nil
@max, @range, @count, @last = max || 10, range || 10, 0, Time.now
end
# Counts retries on every call.
# If these retries are to often - max times in range - it will return false
# else true.
# Now you can say: "I give up, to many retries, it seems it doesn't work."
def retry?
@count = @last + @range > Time.now ? @count + 1 : 1
@last = Time.now
@count < @max
end
def run ex, &e
# Automatical retrieing on raised exceptions in block.
# ex: Your expected Esception you will rescue. Default: Object, so realy everything.
#
# Example:
# Retries.new( 10, 30).run ArgumentError do something_do_which_could_raise_exception ArgumentError end
#
# This will retry maximal 10 times in 30 seconds to Call this block. But only rescues ArgumentError!
# Every other Error it will ignore and throws Exception. No retry.
def run ex = nil, &e
ex ||= Object
begin e.call *args
rescue ex
retries.retry? and retry
@ -51,6 +86,16 @@ class Retries
end
end
# Easy problem-handler for your Server.
#
# A Server should never crash.
# If an Exception raised, which is not rescued, your program will shutdown abnormaly.
# Or if a signal tries to "kill" your program, your program will shutdown abnormaly too.
#
# With RobustServer these errors will be a more unimportant problem and It'll be easier to handle.
#
# Subclasses should implements *#run*, which will be your main-worker.
# For initializing, you can override **#initialize**, but doen't forget to call **super**.
class RobustServer
attr_reader :signals