Source code for piwheels.master.seraph

# The piwheels project
#   Copyright (c) 2017 Ben Nuttall <https://github.com/bennuttall>
#   Copyright (c) 2017 Dave Jones <dave@waveform.org.uk>
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"""
Defines the :class:`Seraph` task; see class for more details.

.. autoclass:: Seraph
    :members:
"""

import zmq
import zmq.error

from .. import const
from .tasks import Task


[docs]class Seraph(Task): """ This task is a simple load-sharing router for :class:`~.the_oracle.TheOracle` tasks. """ name = 'master.seraph' def __init__(self, config): super().__init__(config) self.front_queue = self.ctx.socket(zmq.ROUTER) self.front_queue.hwm = 10 self.front_queue.bind(config.db_queue) self.back_queue = self.ctx.socket(zmq.ROUTER) self.back_queue.hwm = 10 self.back_queue.bind(const.ORACLE_QUEUE) self.workers = [] self.register(self.front_queue, self.handle_front) self.register(self.back_queue, self.handle_back)
[docs] def handle_front(self, queue): """ If any workers are currently available, receive :class:`~.the_oracle.DbClient` requests from the front queue and send it on to the worker including the client's address frame. """ if self.workers: client, _, request = queue.recv_multipart() worker = self.workers.pop(0) self.back_queue.send_multipart([worker, _, client, _, request])
[docs] def handle_back(self, queue): """ Receive a response from an instance of :class:`~.the_oracle.TheOracle` on the back queue. Strip off the worker's address frame and add it back to the available queue then send the response back to the client that made the original request. """ worker, _, *msg = queue.recv_multipart() self.workers.append(worker) if msg != [b'READY']: self.front_queue.send_multipart(msg)