thread_safe_buffer.py

import queue
from software.logger.logger import createLogger
from typing import Type, Optional
from google.protobuf.message import Message


class ThreadSafeBuffer(object):

    MIN_DROPPED_BEFORE_LOG = 20

    """Multiple producer, multiple consumer buffer.

               │              buffer_size                 │
               ├──────────────────────────────────────────┤
               │                                          │

               ┌──────┬──────┬──────┬──────┬──────┬───────┐
         put() │      │      │      │      │      │       │  get()
               └──────┴──────┴──────┴──────┴──────┴───────┘
                                           ThreadSafeBuffer

    """

    def __init__(
        self, buffer_size: int, protobuf_type: Type[Message], log_overrun: bool = False
    ) -> None:

        """A buffer to hold data to be consumed.

        :param buffer size: The size of the buffer.
        :param protobuf_type: To buffer
        :param log_overrun: False

        """
        self.logger = createLogger(protobuf_type.DESCRIPTOR.name + " Buffer")
        self.queue = queue.Queue(buffer_size)
        self.protobuf_type = protobuf_type
        self.log_overrun = log_overrun
        self.cached_msg = protobuf_type()
        self.protos_dropped = 0
        self.last_logged_protos_dropped = 0

    def get(
        self, block: bool = False, timeout: float = None, return_cached: bool = True
    ) -> Optional[Message]:
        """Get data from the buffer.

        If the buffer is empty:

            - If block is True
                - wait until a new msg is received.
                - If a timeout is supplied, wait for timeout seconds
                - Then throw an error, or return cached message if return_cached is True

            - If block is False
                - Return None if return_cached is False
                - Return cached message if return_cached is True

        :param block: If block is True, then block until a new message
                      comes through, or returned the cached msg if return_cached = True
        :param timeout: If block is True, then wait for this many seconds before
                        throwing an error or returning cached
        :param return_cached: If queue is empty, decides whether to
                              return cached value (True) or return None / throw an error (false)

        :return: protobuf (cached if block is False and there is no data
                 in the buffer)

        """

        if (
            self.log_overrun
            and self.protos_dropped > self.last_logged_protos_dropped
            and self.protos_dropped > self.MIN_DROPPED_BEFORE_LOG
        ):
            self.logger.warn(
                "packets dropped; thunderscope did not show {} protos".format(
                    self.protos_dropped
                )
            )
            self.last_logged_protos_dropped = self.protos_dropped

        if block:
            try:
                self.cached_msg = self.queue.get(timeout=timeout)
            except queue.Empty as empty:
                if not return_cached:
                    raise empty
        else:
            try:
                self.cached_msg = self.queue.get_nowait()
            except queue.Empty as empty:
                if not return_cached:
                    return None

        return self.cached_msg

    def put(self, proto: Message, block: bool = False, timeout: float = None) -> None:
        """Put data into the buffer. If the buffer is full, then
        the proto will be logged.

        :param proto: The proto to place in the buffer
        :param block: Should block until there is space in the buffer
        :param timeout: If block is True, then wait for this many seconds

        """
        if block:
            self.queue.put(proto, block, timeout)
            return

        try:
            self.queue.put_nowait(proto)
        except queue.Full as full:
            self.protos_dropped += 1