Ruby Debugging

Thread inspection

• 'th l' lists all threads
• 'th c' shows current thread being debugged
• 'th switch <num>' switches context to given thread number
• 'th stop <num>' stop thread number
• 'th resume <num>' resume execution on thread number

• 
  #!/usr/local/bin/ruby
  
  # from dave & andy's 'programming ruby' book, pg 113-114
  
  require 'net/http'
  pages = %w( www.rubycentral.com www.awl.com www.pragmaticprogrammer.com)
  threads = []
  
  for page in pages
    threads << Thread.new(page) do |myPage|
      h = Net::HTTP.new(myPage, 80)
      puts "Fetching: #{myPage}"
      resp, data = h.get('/', nil)
      puts "Got #{myPage}: #{resp.message}"
    end
  end
  
  threads.each { |aThread| aThread.join }
  

• 
  % ruby -rdebug test-threads
  Debug.rb
  Emacs support available.
  
  test-threads:5:require 'net/http'
  (rdb:1) b 12
  Set breakpoint 1 at test-threads:12
  (rdb:1) c 
  Breakpoint 1, toplevel at test-threads:12
  test-threads:12:    puts "Fetching: #{myPage}"
  (rdb:2) p myPage
  "www.rubycentral.com"
  (rdb:2) th l
   1 #<Thread:0x8078088 sleep>    test-threads:15
  +2 #<Thread:0x80e65b0 run>      test-threads:12
  (rdb:2) n 
  Breakpoint 1, toplevel at test-threads:12
  test-threads:12:    puts "Fetching: #{myPage}"
  (rdb:3) n 
  Fetching: www.rubycentral.comBreakpoint 1, toplevel at test-threads:12
  test-threads:12:    puts "Fetching: #{myPage}"
  (rdb:4) th l
  (rdb:4) th l
   1 #<Thread:0x8078088 sleep>    test-threads:15
   2 #<Thread:0x80e65b0 sleep>    test-threads:12
   3 #<Thread:0x80e3c48 sleep>    test-threads:12
  +4 #<Thread:0x80e11c8 run>      test-threads:12
  (rdb:4) n 
  Fetching: www.awl.com
  test-threads:13:    resp, data = h.get('/', nil)
  (rdb:3) th l
   1 #<Thread:0x8078088 sleep>    test-threads:15
   2 #<Thread:0x80e65b0 sleep>    test-threads:12
  +3 #<Thread:0x80e3c48 run>      test-threads:13
   4 #<Thread:0x80e11c8 sleep>    test-threads:12
  (rdb:3) n 
  test-threads:13:    resp, data = h.get('/', nil)
  (rdb:2) n 
  Fetching: www.pragmaticprogrammer.com
  test-threads:13:    resp, data = h.get('/', nil)
  (rdb:4) n
  /usr/local/lib/ruby/1.6/net/protocol.rb:221: `302 "Moved Temporarily"' (Net::ProtoRetriableError)
          from test-threads:15:in `new'
          from test-threads:15
          from test-threads:9:in `each'
          from test-threads:9
  /usr/local/lib/ruby/1.6/net/protocol.rb:221:      raise @code_type.error_type.new( code + ' ' + msg.dump, self )
  (rdb:3) th l
   1 #<Thread:0x8078088 sleep>    test-threads:18
   2 #<Thread:0x80e65b0 sleep>    /usr/local/lib/ruby/1.6/net/protocol.rb:611
  +3 #<Thread:0x80e3c48 run>      /usr/local/lib/ruby/1.6/net/protocol.rb:221
   4 #<Thread:0x80e11c8 sleep>    /usr/local/lib/ruby/1.6/net/protocol.rb:611
  (rdb:3)