Create with_retry.rb

with_retry.rb

@@ -0,0 +1,88 @@
+#!/usr/bin/env ruby
+
+require 'English'
+require 'pty'
+
+=begin
+  Runs package install until it succeeds or fails 10 times in a row.
+
+  Test cases for testing manually:
+
+  # fails permanently
+  $ ./with_retry.rb ruby -e 'raise "Hello"'
+  $ ./with_retry.rb ruby -e 'exit 2'
+
+  # command not found
+  $ ./with_retry.rb non-existent-command
+
+  # succeeds
+  $ ./with_retry.rb ruby -e 'exit 0'
+  $ ./with_retry.rb ruby -e 'sleep(1); now = `date +%s`.to_i; goal = ARGV[0].to_i + 5; puts "#{now} > #{goal}"; exit (now > goal)' `date +%s`
+=end
+
+def run_command_with_retry(command_and_args)
+  exit_status = nil
+  last_exception = nil
+  10.times do |i|
+    begin
+      last_exception, exit_status = run_command command_and_args
+      exit 0 if exit_status == 0
+    rescue Errno::ENOENT
+      puts "#{command_and_args.first}: command not found"
+      exit 1
+    rescue => e
+      exit_status = e
+    end
+    puts "Attempt ##{i} failure: #{exit_status.class}:\n#{exit_status}"
+  end
+
+  puts "Permanently failed to execute: #{command_and_args.join(' ')}"
+  puts "Last exception from #run_command was: \n #{last_exception.class}: #{last_exception}" if last_exception
+  exit 1
+end
+
+def run_command(command_and_args)
+  last_exception = nil
+  status = nil
+
+  begin
+    PTY.spawn(*command_and_args) do |stdout, _stdin, pid|
+      begin
+        stdout.each { |line| print line }
+      rescue Errno::EIO => e
+        # Errno:EIO error, but this probably just means
+        # that the process has finished giving output
+        last_exception = e
+      ensure
+        # ref:
+        # http://stackoverflow.com/a/10306782/20226
+        # http://stackoverflow.com/a/7263243/20226
+        _pid, status = Process.wait2 pid
+      end
+    end
+
+    # ref:
+    # http://www.shanison.com/2010/09/11/ptychildexited-exception-and-ptys-exit-status/
+    if status.nil?
+      status = if $ERROR_INFO.nil? || $ERROR_INFO.is_a?(SystemExit) && $ERROR_INFO.success?
+                 0
+               else
+                 $ERROR_INFO.is_a?(SystemExit) ? $ERROR_INFO.status.exitstatus : 1
+               end
+    end
+  rescue PTY::ChildExited => e
+    # The child process exited
+    last_exception = e
+    status = e.status
+  end
+  [last_exception, status]
+end
+
+if __FILE__ == $PROGRAM_NAME
+  if ARGV.length > 0
+    run_command_with_retry ARGV
+  else
+    puts "Usage: with_retry.rb command --and your --args of choice"
+    exit 1
+  end
+end