appengine_scripts/skia-tree-status/master_redirect.py

# Copyright (c) 2014 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.

"""Pages that redirect to the currently running Skia Buildbot master."""

# TODO(rmistry): Delete this page when the new rebaseline server is ready.

import httplib
import logging
import urllib2

import base_page


# Static IP addresses of our various services.
REBASELINE_SERVER_IPS = ['108.170.219.43']

# Map of service type to (list_of_possible_ip_addrs, port, subpart, protocol).
# The list_of_possible_ip_addrs, port, and protocol must be specified;
# subpart can be an empty string if not needed.
SERVICE_TYPE_TO_INFO = {
    'rebaseline-server':  (REBASELINE_SERVER_IPS, 10117, '', 'http'),
}
# Timeout to use in urlopen when determining which IP is up.
URLOPEN_TIMEOUT = 15


def _get_destination_url(service_type, slug, query_string=None):
  """Returns a complete destination URL from the service type and slug.

  This function first determines which master from the possible_ips list is up.
  It then constructs a URL using the service type's port, subpart and protocol.
  The specified slug is then appended to this url.

  Args:
    service_type: string; Which service_type to look up in SERVICE_TYPE_TO_INFO.
        If None, use the first path element within slug as the service_type.
    slug: string; Path elements that appengine handed us to deal with--we append
        this to the server-specific URL we create here.
    query_string: string; The query parameters of the URL, everything after the
        first ?. Optional.

  Returns:
    A destination URL.
  """
  if service_type:
    remaining_slug = slug
  elif '/' in slug:
    service_type, remaining_slug = slug.split('/', 1)
  else:
    service_type = slug
    remaining_slug = None

  (possible_ips, port, subpart, protocol) = SERVICE_TYPE_TO_INFO[service_type]
  for ipaddr in possible_ips:
    # The test URL is used for validating that the IP + Port combination is up.
    test_url = 'http://%s:%s' % (ipaddr, port)
    try:
      urllib2.urlopen(test_url, timeout=URLOPEN_TIMEOUT).getcode()
      # Now that we verified that the test URL is up use the service's protocol
      # to construct the destination URL.
      destination_url = '%s://%s:%s' % (protocol, ipaddr, port)
      # Add the subpart and remaining_slug to the destination URL.
      if subpart:
        destination_url += '/%s' % subpart
      if remaining_slug:
        destination_url += '/%s' % remaining_slug
      if query_string:
        destination_url += '?%s' % query_string
      return destination_url
    except httplib.HTTPException, e:
      logging.warning(e)

  error_msg = ('The buildbot master could not be contacted at any of %s' %
               str(possible_ips))
  logging.error(error_msg)
  raise Exception(error_msg)


class GenericRedirectionPage(base_page.BasePage):
  """Generic redirector which lets _get_destination_url() figure out the
  service_type."""
  def get(self, slug, *args):
    destination_url = _get_destination_url(
        service_type=None, slug=slug, query_string=self.request.query_string)
    self.redirect(destination_url, True)