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client-libraries/ruby/lib/better_timeout.rb

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+#--
+# = timeout.rb
+#
+# execution timeout
+#
+# = Copyright
+#
+# Copyright - (C) 2008  Evan Phoenix
+# Copyright:: (C) 2000  Network Applied Communication Laboratory, Inc.
+# Copyright:: (C) 2000  Information-technology Promotion Agency, Japan
+#
+#++
+#
+# = Description
+#
+# A way of performing a potentially long-running operation in a thread, and
+# terminating it's execution if it hasn't finished within fixed amount of
+# time.
+#
+# Previous versions of timeout didn't use a module for namespace. This version
+# provides both Timeout.timeout, and a backwards-compatible #timeout.
+#
+# = Synopsis
+#
+#   require 'timeout'
+#   status = Timeout::timeout(5) {
+#     # Something that should be interrupted if it takes too much time...
+#   }
+#
+
+require 'thread'
+
+module Timeout
+
+  ##
+  # Raised by Timeout#timeout when the block times out.
+
+  class Error<Interrupt
+  end
+
+  # A mutex to protect @requests
+  @mutex = Mutex.new
+
+  # All the outstanding TimeoutRequests
+  @requests = []
+
+  # Represents +thr+ asking for it to be timeout at in +secs+
+  # seconds. At timeout, raise +exc+.
+  class TimeoutRequest
+    def initialize(secs, thr, exc)
+      @left = secs
+      @thread = thr
+      @exception = exc
+    end
+
+    attr_reader :thread, :left
+
+    # Called because +time+ seconds have gone by. Returns
+    # true if the request has no more time left to run.
+    def elapsed(time)
+      @left -= time
+      @left <= 0
+    end
+
+    # Raise @exception if @thread.
+    def cancel
+      if @thread and @thread.alive?
+        @thread.raise @exception, "execution expired"
+      end
+
+      @left = 0
+    end
+
+    # Abort this request, ie, we don't care about tracking
+    # the thread anymore.
+    def abort
+      @thread = nil
+      @left = 0
+    end
+  end
+
+  def self.add_timeout(time, exc)
+
+    @controller ||= Thread.new do
+      while true
+        if @requests.empty?
+          sleep
+          next
+        end
+
+        min = nil
+
+        @mutex.synchronize do
+          min = @requests.min { |a,b| a.left <=> b.left }
+        end
+
+        slept_for = sleep(min.left)
+
+        @mutex.synchronize do
+          @requests.delete_if do |r|
+            if r.elapsed(slept_for)
+              r.cancel
+              true
+            else
+              false
+            end
+          end
+        end
+
+      end
+    end
+
+    req = TimeoutRequest.new(time, Thread.current, exc)
+
+    @mutex.synchronize do
+      @requests << req
+    end
+
+    @controller.run
+
+    return req
+  end
+
+  ##
+  # Executes the method's block. If the block execution terminates before +sec+
+  # seconds has passed, it returns true. If not, it terminates the execution
+  # and raises +exception+ (which defaults to Timeout::Error).
+  #
+  # Note that this is both a method of module Timeout, so you can 'include
+  # Timeout' into your classes so they have a #timeout method, as well as a
+  # module method, so you can call it directly as Timeout.timeout().
+  
+  def timeout(sec, exception=Error)
+    return yield if sec == nil or sec.zero?
+    raise ThreadError, "timeout within critical session" if Thread.critical
+
+    req = Timeout.add_timeout sec, exception
+    
+    begin
+      yield sec
+    ensure
+      req.abort
+    end
+  end
+
+  module_function :timeout
+
+end
+
+##
+# Identical to:
+#
+#   Timeout::timeout(n, e, &block).
+#
+# Defined for backwards compatibility with earlier versions of timeout.rb, see
+# Timeout#timeout.
+
+def timeout(n, e=Timeout::Error, &block) # :nodoc:
+  Timeout::timeout(n, e, &block)
+end
+
+##
+# Another name for Timeout::Error, defined for backwards compatibility with
+# earlier versions of timeout.rb.
+
+TimeoutError = Timeout::Error # :nodoc:
+
+if __FILE__ == $0
+  p timeout(5) {
+    45
+  }
+  p timeout(5, TimeoutError) {
+    45
+  }
+  p timeout(nil) {
+    54
+  }
+  p timeout(0) {
+    54
+  }
+  p timeout(5) {
+    loop {
+      p 10
+      sleep 1
+    }
+  }
+end
+