upstream/mercurial-mirror Files · contrib/debugcmdserver.py

wireprotov2peer: stream decoded responses...

wireprotov2peer: stream decoded responses Previously, wire protocol version 2 would buffer all response data. Only once all data was received did we CBOR decode it and resolve the future associated with the command. This was obviously not desirable. In future commits that introduce large response payloads, this caused significant memory bloat and slowed down client operations due to waiting on the server. This commit refactors the response handling code so that response data can be streamed. Command response objects now contain a buffered CBOR decoder. As new data arrives, it is fed into the decoder. Decoded objects are made available to the generator as they are decoded. Because there is a separate thread processing incoming frames and feeding data into the response object, there is the potential for race conditions when mutating response objects. So a lock has been added to guard access to critical state variables. Because the generator emitting decoded objects needs to wait on those objects to become available, we've added an Event for the generator to wait on so it doesn't busy loop. This does mean there is the potential for deadlocks. And I'm pretty sure they can occur in some scenarios. We already have a handful of TODOs around this. But I've added some more. Fixing this will likely require moving the background thread receiving frames into clienthandler. We likely would have done this anyway when implementing the client bits for the SSH transport. Test output changes because the initial CBOR map holding the overall response state is now always handled internally by the response object. Differential Revision: https://phab.mercurial-scm.org/D4474

Pulkit Goyal - - Load All Authors

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             debugcmdserver.py
        
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      #!/usr/bin/env python

      #

      # Dumps output generated by Mercurial's command server in a formatted style to a

      # given file or stderr if '-' is specified. Output is also written in its raw

      # format to stdout.

      #

      # $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -

      # o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

      from __future__ import absolute_import, print_function

      import struct

      import sys

      if len(sys.argv) != 2:

          print('usage: debugcmdserver.py FILE')

          sys.exit(1)

      outputfmt = '>cI'

      outputfmtsize = struct.calcsize(outputfmt)

      if sys.argv[1] == '-':

          log = sys.stderr

      else:

          log = open(sys.argv[1], 'a')

      def read(size):

          data = sys.stdin.read(size)

          if not data:

              raise EOFError

          sys.stdout.write(data)

          sys.stdout.flush()

          return data

      try:

          while True:

              header = read(outputfmtsize)

              channel, length = struct.unpack(outputfmt, header)

              log.write('%s, %-4d' % (channel, length))

              if channel in 'IL':

                  log.write(' -> waiting for input\n')

              else:

                  data = read(length)

                  log.write(' -> %r\n' % data)

              log.flush()

      except EOFError:

          pass

      finally:

          if log != sys.stderr:

              log.close()

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				#!/usr/bin/env python
				#
				# Dumps output generated by Mercurial's command server in a formatted style to a
				# given file or stderr if '-' is specified. Output is also written in its raw
				# format to stdout.
				#
				# $ ./hg serve --cmds pipe \| ./contrib/debugcmdserver.py -
				# o, 52 -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

				from __future__ import absolute_import, print_function
				import struct
				import sys

				if len(sys.argv) != 2:
				print('usage: debugcmdserver.py FILE')
				sys.exit(1)

				outputfmt = '>cI'
				outputfmtsize = struct.calcsize(outputfmt)

				if sys.argv[1] == '-':
				log = sys.stderr
				else:
				log = open(sys.argv[1], 'a')

				def read(size):
				data = sys.stdin.read(size)
				if not data:
				raise EOFError
				sys.stdout.write(data)
				sys.stdout.flush()
				return data

				try:
				while True:
				header = read(outputfmtsize)
				channel, length = struct.unpack(outputfmt, header)
				log.write('%s, %-4d' % (channel, length))
				if channel in 'IL':
				log.write(' -> waiting for input\n')
				else:
				data = read(length)
				log.write(' -> %r\n' % data)
				log.flush()
				except EOFError:
				pass
				finally:
				if log != sys.stderr:
				log.close()