tools/perf/core/services/request.py

# Copyright 2018 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import json
import logging
import urllib

import httplib2

from py_utils import retry_util  # pylint: disable=import-error

from core.services import luci_auth


# Some services pad JSON responses with a security prefix to prevent against
# XSSI attacks. If found, the prefix is stripped off before attempting to parse
# a JSON response.
# See e.g.: https://gerrit-review.googlesource.com/Documentation/rest-api.html#output
JSON_SECURITY_PREFIX = ")]}'"


class RequestError(OSError):
  """Exception class for errors while making a request."""
  def __init__(self, request, response, content):
    self.request = request
    self.response = response
    self.content = content
    message = u'%s returned HTTP Error %d: %s' % (
        self.request, self.response.status, self.error_message)
    # Note: the message is a unicode object, possibly with special characters,
    # so it needs to be turned into a str as expected by the constructor of
    # the base class.
    super(RequestError, self).__init__(message.encode('utf-8'))

  def __reduce__(self):
    # Method needed to make the exception pickleable [1], otherwise it causes
    # the multiprocess pool to hang when raised by a worker [2].
    # [1]: https://stackoverflow.com/a/36342588
    # [2]: https://github.com/uqfoundation/multiprocess/issues/33
    return (type(self), (self.request, self.response, self.content))

  @property
  def json(self):
    """Attempt to load the content as a json object."""
    try:
      return json.loads(self.content)
    except StandardError:
      return None

  @property
  def error_message(self):
    """Returns a unicode object with the error message found in the content."""
    try:
      # Try to find error message within json content.
      return self.json['error']
    except StandardError:
      # Otherwise fall back to entire content itself, converting str to unicode.
      return self.content.decode('utf-8')


class ClientError(RequestError):
  """Exception for 4xx HTTP client errors."""
  pass


class ServerError(RequestError):
  """Exception for 5xx HTTP server errors."""
  pass


def BuildRequestError(request, response, content):
  """Build the correct RequestError depending on the response status."""
  if response['status'].startswith('4'):
    error = ClientError
  elif response['status'].startswith('5'):
    error = ServerError
  else:  # Fall back to the base class.
    error = RequestError
  return error(request, response, content)


@retry_util.RetryOnException(ServerError, retries=3)
def Request(url, method='GET', params=None, data=None, accept=None,
            content_type='urlencoded', use_auth=False, retries=None):
  """Perform an HTTP request of a given resource.

  Args:
    url: A string with the URL to request.
    method: A string with the HTTP method to perform, e.g. 'GET' or 'POST'.
    params: An optional dict or sequence of key, value pairs to be added as
      a query to the url.
    data: An optional dict or sequence of key, value pairs to send as payload
      data in the body of the request.
    accept: An optional string to specify the expected response format.
      Currently only 'json' is supported, which attempts to parse the response
      content as json. If omitted, the default is to return the raw response
      content as a string.
    content_type: A string specifying how to encode the payload data,
      can be either 'urlencoded' (default) or 'json'.
    use_auth: A boolean indecating whether to send authorized requests, if True
      luci-auth is used to get an access token for the logged in user.
    retries: Number of times to retry the request in case of ServerError. Note,
      the request is _not_ retried if the response is a ClientError.

  Returns:
    A string with the content of the response when it has a successful status.

  Raises:
    A ClientError if the response has a 4xx status, or ServerError if the
    response has a 5xx status.
  """
  del retries  # Handled by the decorator.

  if params:
    url = '%s?%s' % (url, urllib.urlencode(params))

  body = None
  headers = {}

  if accept == 'json':
    headers['Accept'] = 'application/json'
  elif accept is not None:
    raise NotImplementedError('Invalid accept format: %s' % accept)

  if data is not None:
    if content_type == 'json':
      body = json.dumps(data, sort_keys=True, separators=(',', ':'))
      headers['Content-Type'] = 'application/json'
    elif content_type == 'urlencoded':
      body = urllib.urlencode(data)
      headers['Content-Type'] = 'application/x-www-form-urlencoded'
    else:
      raise NotImplementedError('Invalid content type: %s' % content_type)
  else:
    headers['Content-Length'] = '0'

  if use_auth:
    headers['Authorization'] = 'Bearer %s' % luci_auth.GetAccessToken()

  logging.info('Making API request: %s', url)
  http = httplib2.Http()
  response, content = http.request(
      url, method=method, body=body, headers=headers)
  if response.status != 200:
    raise BuildRequestError(url, response, content)

  if accept == 'json':
    if content[:4] == JSON_SECURITY_PREFIX:
      content = content[4:]  # Strip off security prefix if found.
    content = json.loads(content)
  return content