231 lines
6.9 KiB
Python
231 lines
6.9 KiB
Python
# Copyright (c) 2015-2016 OpenStack Foundation
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from functools import partial
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import json
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import os
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import signal
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from storlets.sbus import SBus
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import storlets.sbus.command as sbus_cmd
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EXIT_SUCCESS = 0
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EXIT_FAILURE = 1
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LOOP_TIMEOUT = 0.5
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LISTEN_TIMEOUT = 300
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class CommandResponse(Exception):
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"""
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The result of command execution
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"""
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def __init__(self, status, message, iterable=True, task_id=None):
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"""
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Construct CommandResponse instance
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:param status: task status
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:param message: message to be returned and logged
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:param iterable: whether we can keep SDaemon process running
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:param task_id: ID assigned to the requested task
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"""
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self.status = status
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self.message = message
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# NOTE(takashi): iterable controls whether the server main loop should
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# exit or not as a result of processing the command
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self.iterable = iterable
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self.task_id = task_id
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@property
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def report_message(self):
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rsp = {'status': self.status, 'message': self.message}
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if self.task_id:
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rsp['task_id'] = self.task_id
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return json.dumps(rsp)
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CommandSuccess = partial(CommandResponse, True)
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CommandFailure = partial(CommandResponse, False)
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def command_handler(func):
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"""
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Decorator for handler methods called according to given sbus command
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"""
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func.is_command_handler = True
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return func
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class SBusServer(object):
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"""
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Basic implementation for server processes listening on sbus protocol
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NOTE(takash): we should implement some termination functions like
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_terminate and halt, otherwise they raise
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NotImplementedError.
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"""
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def __init__(self, sbus_path, logger):
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self.sbus_path = sbus_path
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self.logger = logger
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self.running = True
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self.listen_timeout = LISTEN_TIMEOUT
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self.loop_timeout = LOOP_TIMEOUT
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def get_handler(self, command):
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"""
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Decide handler function corresponding to the received command
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:param command: command
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:returns: handler function
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"""
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# All commands should be defined in storlets.sbus.command
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if not hasattr(sbus_cmd, command):
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raise ValueError('Unknown command %s' % command)
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func_name = command[len(sbus_cmd.SBUS_CMD_PREFIX):].lower()
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try:
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handler = getattr(self, func_name)
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getattr(handler, 'is_command_handler')
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except AttributeError:
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raise ValueError('Command %s is not allowed for this server' %
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command)
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return handler
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def dispatch_command(self, dtg):
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"""
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Parse datagram. React on the request.
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:param dtg: Datagram received from client
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:returns: True if the server can continue its main loop
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False if the server should terminate its main loop
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"""
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command = dtg.command
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self.logger.debug("Received command %s" % command)
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try:
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handler = self.get_handler(command)
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resp = handler(dtg)
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except ValueError as err:
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self.logger.exception('Failed to handle request')
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resp = CommandFailure(str(err))
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except CommandResponse as err:
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resp = err
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except Exception:
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self.logger.exception('Failed to handle request')
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resp = CommandFailure('Internal error')
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self.logger.info('Command:%s Response:%s' %
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(command, resp.report_message))
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outfd = dtg.service_out_fd
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with os.fdopen(outfd, 'wb') as outfile:
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self._respond(outfile, resp)
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return resp.iterable
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def _respond(self, outfile, resp):
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"""
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Send result description message back to gateway
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:param outfile : Output channel to send the message to
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:param resp: CommandResponse instance
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"""
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try:
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outfile.write(resp.report_message.encode('utf-8'))
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except IOError:
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self.logger.exception('Unable to return response to client')
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@command_handler
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def ping(self, dtg):
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self.logger.debug('Received ping. Responding')
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return CommandSuccess('OK')
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@command_handler
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def halt(self, dtg):
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raise NotImplementedError()
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def _terminate(self):
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raise NotImplementedError()
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def _force_terminate(self):
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raise NotImplementedError()
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def _graceful_shutdown(self, *args):
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self.logger.info("received SIGHUP. Shutting down gracefully")
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self.running = False
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def _force_shutdown(self, *args):
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self.logger.info("received SIGTERM. Shutting down now")
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try:
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self._force_terminate()
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except Exception:
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self.logger.exception(
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"Failed to force_terminate. The process stops anyway")
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finally:
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os._exit(1)
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def main_loop(self):
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"""
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Main loop to run storlet application
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:returns: EXIT_SUCCESS when the loop exists normally
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EXIT_FAILURE when an error occurs in main loop
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"""
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sbus = SBus()
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fd = sbus.create(self.sbus_path)
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if fd < 0:
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self.logger.error("Failed to create SBus. exiting.")
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return EXIT_FAILURE
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signal.signal(signal.SIGHUP, self._graceful_shutdown)
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signal.signal(signal.SIGTERM, self._force_shutdown)
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loop_cnt = 0
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status = EXIT_SUCCESS
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while self.running:
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rc = sbus.listen(fd, self.loop_timeout)
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if rc < 0:
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self.logger.error("Failed to wait on SBus. exiting.")
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status = EXIT_FAILURE
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break
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elif rc == 0:
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loop_cnt += 1
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if loop_cnt * self.loop_timeout >= self.listen_timeout:
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self.logger.debug("Timed out while listening. exiting.")
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break
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continue
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# Reset loop_cnt here as a request comes via sbus
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loop_cnt = 0
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dtg = sbus.receive(fd)
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if dtg is None:
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self.logger.error("Failed to receive message. exiting")
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status = EXIT_FAILURE
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break
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if not self.dispatch_command(dtg):
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break
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self.logger.debug('Leaving main loop')
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self._terminate()
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return status
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