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Source code for google.appengine.api.backends.backends
#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Backends API.
.. deprecated:: 1.9.1
Use Modules library instead.
This API provides utility methods for working with backends.
"""
import logging
import os
import re
from google.appengine.api import app_identity
from google.appengine.api import modules
[docs]class Error(Exception):
"""Base class for exceptions in this module."""
[docs]class DefaultHostnameError(Error):
"""Raised if no default hostname is set in the environment."""
[docs]class InvalidBackendError(Error):
"""Raised if an invalid backend was provided."""
pass
[docs]class InvalidInstanceError(Error):
"""Raised if an invalid instance was provided."""
pass
logging.warning('The Backends API is deprecated and will be removed in a '
'future release. Please migrate to the Modules API as soon as '
'possible.')
[docs]def get_backend():
"""DEPRECATED: Get the name of the backend handling this request.
Warning: This API is deprecated and will be removed in a future
release. Please migrate to the Modules API as soon as possible.
Returns:
string: The current backend, or None if this is not a backend.
"""
return os.environ.get('BACKEND_ID', None)
[docs]def get_instance():
"""DEPRECATED: Get the instance number of the backend handling this request.
Warning: This API is deprecated and will be removed in a future
release. Please migrate to the Modules API as soon as possible.
Returns:
int: The instance, in [0, instances-1], or None if this is not a backend.
"""
instance = os.environ.get('INSTANCE_ID', None)
if instance is not None:
return int(instance)
else:
return None
[docs]def get_url(backend=None, instance=None, protocol='http'):
"""DEPRECATED: Returns a URL pointing to a backend or backend instance.
Warning: This API is deprecated and will be removed in a future
release. Please migrate to the Modules API as soon as possible.
This method works in both production and development environments.
Args:
backend: The name of the backend. If None, the current backend will be used.
instance: An optoinal instance number. If provided, the URL will target
the specific instance. If absent, the URL will point to a load-balancing
hostname for the backend.
protocol: The protocol to use (default='http').
Raises:
InvalidBackendError
InvalidInstanceError
Returns:
The URL of the backend or backend instance.
"""
if backend is None:
backend = get_backend()
if _is_dev2_environment():
return _get_dev2_url(backend, instance)
elif _is_dev_environment():
return _get_dev_url(backend, instance)
hostname = get_hostname(backend, instance)
return '%s://%s' % (protocol, hostname)
[docs]def get_hostname(backend=None, instance=None):
"""DEPRECATED: Returns the hostname for a backend or backend instance.
Warning: This API is deprecated and will be removed in a future
release. Please migrate to the Modules API as soon as possible.
Args:
backend: The name of the backend. If None, the current backend will be used.
instance: An optoinal instance number. If provided, the hostname will
represent the specific instance. If absent, the hostname will represent
the backend as a whole.
Raises:
InvalidBackendError
InvalidInstanceError
Returns:
The hostname of the backend or backend instance.
"""
if backend is None:
backend = get_backend()
if not isinstance(backend, (str, unicode)):
raise InvalidBackendError('Invalid backend: %s' % backend)
if not re.match('^[a-zA-Z0-9\-]+$', backend):
raise InvalidBackendError('Invalid backend: %s' % backend)
if instance is not None:
try:
instance = int(instance)
except ValueError:
raise InvalidInstanceError('instance must be an integer.')
if _is_dev2_environment():
return _get_dev2_hostname(backend, instance)
elif _is_dev_environment():
return _get_dev_hostname(backend, instance)
hostname = app_identity.get_default_version_hostname()
if hostname is None:
raise DefaultHostnameError
hostname = '%s.%s' % (backend, hostname)
if instance is not None:
hostname = '%d.%s' % (instance, hostname)
return hostname
def _is_dev2_environment():
"""Indicates whether this code is being run in devappserver2."""
return os.environ.get('SERVER_SOFTWARE', '') == 'Development/2.0'
def _get_dev2_url(backend, instance=None):
"""Returns the url of a backend [instance] in devappserver2.
Args:
backend: The name of the backend.
instance: The backend instance number, in [0, instances-1].
Returns:
The url of the backend.
"""
return 'http://%s' % _get_dev2_hostname(backend, instance)
def _get_dev2_hostname(backend, instance=None):
"""Returns the hostname of a backend [instance] in devappserver2.
Args:
backend: The name of the backend.
instance: The backend instance number, in [0, instances-1].
Returns:
The hostname of the backend.
"""
try:
return modules.get_hostname(module=backend, instance=instance)
except modules.InvalidModuleError:
raise InvalidBackendError()
except modules.InvalidInstancesError:
raise InvalidInstanceError()
def _is_dev_environment():
"""Indicates whether this code is being run in the development environment."""
return os.environ.get('SERVER_SOFTWARE', '').startswith('Development')
def _get_dev_url(backend, instance=None):
"""Returns the url of a backend [instance] in the dev_appserver.
Args:
backend: The name of the backend.
instance: The backend instance number, in [0, instances-1].
Returns:
The url of the backend.
"""
return 'http://%s' % _get_dev_hostname(backend, instance)
def _get_dev_hostname(backend, instance=None):
"""Returns the hostname of a backend [instance] in the dev_appserver.
Args:
backend: The name of the backend.
instance: The backend instance number, in [0, instances-1].
Returns:
The hostname of the backend.
"""
port = _get_dev_port(backend, instance)
if not port:
error = 'Backend not found: %s' % backend
if instance is not None:
error = '%s.%d' % (error, instance)
raise InvalidBackendError(error)
host = os.environ.get('SERVER_NAME', 'localhost')
return '%s:%d' % (host, port)
def _get_dev_port(backend, instance=None):
"""Returns the port for a backend [instance] in the dev_appserver.
Args:
backend: The name of the backend.
instance: The backend instance (optional).
Returns:
int: The backend port.
"""
port = os.environ.get(_get_dev_port_var(backend, instance), None)
if port:
return int(port)
else:
return None
def _set_dev_port(port, backend, instance=None, env=os.environ):
"""Sets the port for a backend [instance] in the dev_appserver.
Args:
port: The port.
backend: The name of the backend.
instance: The backend instance (optional).
env: The environment in which to set the port.
"""
env[_get_dev_port_var(backend, instance)] = str(port)
def _get_dev_port_var(backend, instance=None):
"""Return the environment variable for a backend port.
Backend ports are stored at GET_PORT_<backend> for backends
and GET_PORT_<backend>.<instance> for individual instances.
Args:
backend: The name of the backend.
instance: The backend instance (optional).
Returns:
string: The environment variable where the backend port is stored.
"""
port_var = 'BACKEND_PORT.%s' % str(backend).lower()
if instance is not None:
port_var = '%s.%d' % (port_var, instance)
return port_var
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2023-04-04 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2023-04-04 UTC."],[[["This code provides a deprecated API for working with backends in Google App Engine, and users are directed to use the Modules API instead."],["The `get_backend()` and `get_instance()` functions retrieve the backend name and instance number, respectively, but are deprecated."],["The `get_url()` function constructs a URL pointing to a backend or a specific backend instance, and is also deprecated."],["The `get_hostname()` function retrieves the hostname for a backend or backend instance, and this function is deprecated as well."],["The code defines error classes, such as `Error`, `DefaultHostnameError`, `InvalidBackendError`, and `InvalidInstanceError`, to handle specific exceptions."]]],[]]
