sdk/platform-tools/systrace/catapult/telemetry/telemetry/internal/backends/chrome_inspector/devtools_http.py

   1 # Copyright 2014 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 import errno
   6 import httplib
   7 import json
   8 import socket
   9 import sys
  10
  11 from telemetry.core import exceptions
  12
  13
  14 class DevToolsClientConnectionError(exceptions.Error):
  15   pass
  16
  17
  18 class DevToolsClientUrlError(DevToolsClientConnectionError):
  19   pass
  20
  21
  22 class DevToolsHttp(object):
  23   """A helper class to send and parse DevTools HTTP requests.
  24
  25   This class maintains a persistent http connection to Chrome devtools.
  26   Ideally, owners of instances of this class should call Disconnect() before
  27   disposing of the instance. Otherwise, the connection will not be closed until
  28   the instance is garbage collected.
  29   """
  30
  31   def __init__(self, devtools_port):
  32     self._devtools_port = devtools_port
  33     self._conn = None
  34
  35   def __del__(self):
  36     self.Disconnect()
  37
  38   def _Connect(self, timeout):
  39     """Attempts to establish a connection to Chrome devtools."""
  40     assert not self._conn
  41     try:
  42       host_port = '127.0.0.1:%i' % self._devtools_port
  43       self._conn = httplib.HTTPConnection(host_port, timeout=timeout)
  44     except (socket.error, httplib.HTTPException) as e:
  45       raise DevToolsClientConnectionError, (e,), sys.exc_info()[2]
  46
  47   def Disconnect(self):
  48     """Closes the HTTP connection."""
  49     if not self._conn:
  50       return
  51
  52     try:
  53       self._conn.close()
  54     except (socket.error, httplib.HTTPException) as e:
  55       raise DevToolsClientConnectionError, (e,), sys.exc_info()[2]
  56     finally:
  57       self._conn = None
  58
  59   def Request(self, path, timeout=30):
  60     """Sends a request to Chrome devtools.
  61
  62     This method lazily creates an HTTP connection, if one does not already
  63     exist.
  64
  65     Args:
  66       path: The DevTools URL path, without the /json/ prefix.
  67       timeout: Timeout defaults to 30 seconds.
  68
  69     Raises:
  70       DevToolsClientConnectionError: If the connection fails.
  71     """
  72     assert timeout
  73
  74     if not self._conn:
  75       self._Connect(timeout)
  76
  77     endpoint = '/json'
  78     if path:
  79       endpoint += '/' + path
  80     if self._conn.sock:
  81       self._conn.sock.settimeout(timeout)
  82     else:
  83       self._conn.timeout = timeout
  84
  85     try:
  86       # By default, httplib avoids going through the default system proxy.
  87       self._conn.request('GET', endpoint)
  88       response = self._conn.getresponse()
  89       return response.read()
  90     except (socket.error, httplib.HTTPException) as e:
  91       self.Disconnect()
  92       if isinstance(e, socket.error) and e.errno == errno.ECONNREFUSED:
  93         raise DevToolsClientUrlError, (e,), sys.exc_info()[2]
  94       raise DevToolsClientConnectionError, (e,), sys.exc_info()[2]
  95
  96   def RequestJson(self, path, timeout=30):
  97     """Sends a request and parse the response as JSON.
  98
  99     Args:
 100       path: The DevTools URL path, without the /json/ prefix.
 101       timeout: Timeout defaults to 30 seconds.
 102
 103     Raises:
 104       DevToolsClientConnectionError: If the connection fails.
 105       ValueError: If the response is not a valid JSON.
 106     """
 107     return json.loads(self.Request(path, timeout))