# Copyright (c) 2015 The University of Manchester
#
# 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
#
# https://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.
import sys
from threading import RLock
import time
from spinnman.messages.scp.enums import SCPResult
from spinnman.exceptions import SpinnmanTimeoutException, SpinnmanIOException
from spinnman.constants import SCP_TIMEOUT, N_RETRIES
MAX_SEQUENCE = 65536
RETRY_CODES = frozenset([
SCPResult.RC_TIMEOUT, SCPResult.RC_P2P_TIMEOUT, SCPResult.RC_LEN,
SCPResult.RC_P2P_NOREPLY])
# Keep a global track of the sequence numbers used
_next_sequence = 0
_next_sequence_lock = RLock()
[docs]class SCPRequestPipeLine(object):
"""
Allows a set of SCP requests to be grouped together in a communication
across a number of channels for a given connection.
This class implements an SCP windowing, first suggested by Andrew Mundy.
This extends the idea by having both send and receive windows.
These are represented by the n_channels and the
intermediate_channel_waits parameters respectively. This seems to
help with the timeout issue; when a timeout is received, all requests
for which a reply has not been received can also timeout.
"""
__slots__ = [
"_callbacks",
"_connection",
"_error_callbacks",
"_in_progress",
"_intermediate_channel_waits",
"_n_channels",
"_n_resent",
"_n_retries",
"_n_retry_code_resent",
"_n_timeouts",
"_packet_timeout",
"_retry_reason",
"_request_data",
"_requests",
"_retries",
"_send_time",
"_times_sent"]
def __init__(self, connection, n_channels=1,
intermediate_channel_waits=0,
n_retries=N_RETRIES, packet_timeout=SCP_TIMEOUT):
"""
:param SCAMPConnection connection:
The connection over which the communication is to take place
:param int n_channels: The number of requests to send before checking
for responses. If `None`, this will be determined automatically
:param int intermediate_channel_waits: The number of outstanding
responses to wait for before continuing sending requests.
If `None`, this will be determined automatically
:param int n_retries: The number of times to resend any packet for any
reason before an error is triggered
:param float packet_timeout: The number of elapsed seconds after
sending a packet before it is considered a timeout.
"""
self._connection = connection
self._n_channels = n_channels
self._intermediate_channel_waits = intermediate_channel_waits
self._n_retries = n_retries
self._packet_timeout = packet_timeout
if (self._n_channels is not None and
self._intermediate_channel_waits is None):
self._intermediate_channel_waits = self._n_channels - 8
if self._intermediate_channel_waits < 0:
self._intermediate_channel_waits = 0
# A dictionary of sequence number -> requests in progress
self._requests = dict()
self._request_data = dict()
# A dictionary of sequence number -> time at which sequence was sent
self._times_sent = dict()
# A dictionary of sequence number -> number of retries for the packet
self._retries = dict()
# A dictionary of sequence number -> callback function for response
self._callbacks = dict()
# A dictionary of sequence number -> callback function for errors
self._error_callbacks = dict()
# A dictionary of sequence number -> retry reason
self._retry_reason = dict()
# The number of responses outstanding
self._in_progress = 0
# The number of timeouts that occurred
self._n_timeouts = 0
# The number of packets that have been resent
self._n_resent = 0
self._n_retry_code_resent = 0
# self._token_bucket = TokenBucket(43750, 4375000)
# self._token_bucket = TokenBucket(3408, 700000)
def _get_next_sequence_number(self):
"""
Get the next number from the global sequence, applying appropriate
wrapping rules as the sequence numbers have a fixed number of bits.
:return: The next number in the sequence.
:rtype: int
"""
# pylint: disable=global-statement
global _next_sequence
with _next_sequence_lock:
sequence = _next_sequence
_next_sequence = (sequence + 1) % MAX_SEQUENCE
return sequence
[docs] def send_request(self, request, callback, error_callback):
"""
Add an SCP request to the set to be sent.
:param AbstractSCPRequest request: The SCP request to be sent
:param ~collections.abc.Callable callback:
A callback function to call when the response has been received;
takes a :py:class:`SCPResponse` as a parameter, or `None` if the
response doesn't need to be processed
:param ~collections.abc.Callable error_callback:
A callback function to call when an error is found when processing
the message; takes the original :py:class:`AbstractSCPRequest`, the
exception caught and a list of tuples of (filename, line number,
function name, text) as a traceback
"""
# If the connection has not been measured
if self._n_channels is None:
if self._connection.is_ready_to_receive():
self._n_channels = self._in_progress + 8
if self._n_channels < 12:
self._n_channels = 12
self._intermediate_channel_waits = self._n_channels - 8
# If all the channels are used, start to receive packets
while (self._n_channels is not None and
self._in_progress >= self._n_channels):
self._do_retrieve(
self._intermediate_channel_waits, self._packet_timeout)
# Get the next sequence to be used
sequence = self._get_next_sequence_number()
# Update the packet and store required details
request.scp_request_header.sequence = sequence
request_data = self._connection.get_scp_data(request)
self._requests[sequence] = request
self._request_data[sequence] = request_data
self._retries[sequence] = self._n_retries
self._callbacks[sequence] = callback
self._error_callbacks[sequence] = error_callback
self._retry_reason[sequence] = list()
# Send the request, keeping track of how many are sent
# self._token_bucket.consume(284)
self._connection.send(request_data)
self._in_progress += 1
[docs] def finish(self):
"""
Indicate the end of the packets to be sent. This must be called
to ensure that all responses are received and handled.
"""
while self._in_progress > 0:
self._do_retrieve(0, self._packet_timeout)
@property
def n_timeouts(self):
"""
The number of timeouts that occurred.
:rtype: int
"""
return self._n_timeouts
@property
def n_channels(self):
"""
The number of requests to send before checking for responses.
:rtype: int
"""
return self._n_channels
@property
def n_resent(self):
"""
The number of packets that have been resent.
:rtype: int
"""
return self._n_resent
@property
def n_retry_code_resent(self):
"""
The number of resends due to reasons for which automated retry is
the correct response in-protocol.
:rtype: int
"""
return self._n_retry_code_resent
def _remove_record(self, seq):
if seq in self._requests:
del self._requests[seq]
del self._request_data[seq]
del self._retries[seq]
del self._callbacks[seq]
del self._error_callbacks[seq]
del self._retry_reason[seq]
def _single_retrieve(self, timeout):
# Receive the next response
result, seq, raw_data, offset = \
self._connection.receive_scp_response(timeout)
# Only process responses which have matching requests
if seq in self._requests:
self._in_progress -= 1
request_sent = self._requests[seq]
# If the response can be retried, retry it
if result in RETRY_CODES:
try:
time.sleep(0.1)
self._resend(seq, request_sent, str(result))
self._n_retry_code_resent += 1
except Exception as e: # pylint: disable=broad-except
self._error_callbacks[seq](
request_sent, e, sys.exc_info()[2],
self._connection)
self._remove_record(seq)
else:
# No retry is possible - try constructing the result
try:
response = request_sent.get_scp_response()
response.read_bytestring(raw_data, offset)
if self._callbacks[seq] is not None:
self._callbacks[seq](response)
except Exception as e: # pylint: disable=broad-except
self._error_callbacks[seq](
request_sent, e, sys.exc_info()[2],
self._connection)
# Remove the sequence from the outstanding responses
self._remove_record(seq)
def _handle_receive_timeout(self):
self._n_timeouts += 1
# If there is a timeout, all packets remaining are resent
to_remove = list()
for seq, request_sent in self._requests.items():
self._in_progress -= 1
try:
self._resend(seq, request_sent, "timeout")
except Exception as e: # pylint: disable=broad-except
self._error_callbacks[seq](
request_sent, e, sys.exc_info()[2],
self._connection)
to_remove.append(seq)
for seq in to_remove:
self._remove_record(seq)
def _resend(self, seq, request_sent, reason):
if self._retries[seq] <= 0:
# Report timeouts as timeout exception
if all(reason == "timeout" for reason in self._retry_reason[seq]):
raise SpinnmanTimeoutException(
request_sent,
self._packet_timeout)
# Report any other exception
raise SpinnmanIOException(
f"Errors sending request {request_sent} to "
f"{request_sent.sdp_header.destination_chip_x}, "
f"{request_sent.sdp_header.destination_chip_y}, "
f"{request_sent.sdp_header.destination_cpu} over "
f"{self._n_retries} retries: {self._retry_reason[seq]}")
# If the request can be retried, retry it
self._retries[seq] -= 1
self._in_progress += 1
self._requests[seq] = request_sent
self._retry_reason[seq].append(reason)
self._connection.send(self._request_data[seq])
self._n_resent += 1
def _do_retrieve(self, n_packets, timeout):
"""
Receives responses until there are only n_packets responses left.
:param int n_packets:
The number of packets that can remain after running
"""
# While there are still more packets in progress than some threshold
while self._in_progress > n_packets:
try:
# Receive the next response
self._single_retrieve(timeout)
except SpinnmanTimeoutException:
self._handle_receive_timeout()