def _loop(mailbox, channels, archive_name):
"""Main server loop. Intended to be a Process target (and private to this
module). Accepts messages through its mailbox queue, and takes the
appropriate action based on the command and parameters contained within the
message.
Parameters
----------
mailbox : Queue
Used for inter-process communication.
channels : list of str
list of channel names in the underlying data table. Any records
written to the buffer are expected to have an entry for each
channel.
archive_name : str
sqlite database name
"""
buf = Buffer(channels=channels, archive_name=archive_name)
while True:
# Messages should be tuples with the structure:
# (sender, (command, params))
# where sender is either None or a Queue.
msg = mailbox.get()
sender, body = msg
command, params = body
if command == MSG_EXIT:
delete_archive = params
buf.cleanup(delete_archive=delete_archive)
sender.put(('exit', 'ok'))
break
elif command == MSG_PUT:
record = params
buf.append(record)
elif command == MSG_GET_ALL:
sender.put(buf.all())
elif command == MSG_COUNT:
sender.put(len(buf))
elif command == MSG_QUERY_SLICE:
start, end, field = params
logging.debug("Sending query: {}".format((start, end, field)))
sender.put(buf.query(start, end, field))
elif command == MSG_QUERY:
# Generic query
filters, ordering, max_results = params
sender.put(buf.query_data(filters, ordering, max_results))
elif command == MSG_STARTED:
sender.put(('started', 'ok'))
else:
logging.debug("Error; message not understood: {}".format(msg))
