595 lines
17 KiB
Python
595 lines
17 KiB
Python
# piker: trading gear for hackers
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# Copyright (C) Tyler Goodlet (in stewardship for piker0)
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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"""
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NumPy compatible shared memory buffers for real-time IPC streaming.
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"""
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from __future__ import annotations
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from sys import byteorder
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from typing import Optional
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from multiprocessing.shared_memory import SharedMemory, _USE_POSIX
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from multiprocessing import resource_tracker as mantracker
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if _USE_POSIX:
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from _posixshmem import shm_unlink
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import tractor
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import numpy as np
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from pydantic import BaseModel
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from ..log import get_logger
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from ._source import base_iohlc_dtype
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log = get_logger(__name__)
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# how much is probably dependent on lifestyle
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_secs_in_day = int(60 * 60 * 24)
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# we try for 3 times but only on a run-every-other-day kinda week.
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_default_size = 10 * _secs_in_day
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# where to start the new data append index
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_rt_buffer_start = int(9*_secs_in_day)
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# Tell the "resource tracker" thing to fuck off.
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class ManTracker(mantracker.ResourceTracker):
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def register(self, name, rtype):
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pass
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def unregister(self, name, rtype):
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pass
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def ensure_running(self):
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pass
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# "know your land and know your prey"
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# https://www.dailymotion.com/video/x6ozzco
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mantracker._resource_tracker = ManTracker()
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mantracker.register = mantracker._resource_tracker.register
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mantracker.ensure_running = mantracker._resource_tracker.ensure_running
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ensure_running = mantracker._resource_tracker.ensure_running
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mantracker.unregister = mantracker._resource_tracker.unregister
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mantracker.getfd = mantracker._resource_tracker.getfd
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class SharedInt:
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"""Wrapper around a single entry shared memory array which
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holds an ``int`` value used as an index counter.
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"""
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def __init__(
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self,
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shm: SharedMemory,
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) -> None:
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self._shm = shm
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@property
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def value(self) -> int:
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return int.from_bytes(self._shm.buf, byteorder)
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@value.setter
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def value(self, value) -> None:
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self._shm.buf[:] = value.to_bytes(self._shm.size, byteorder)
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def destroy(self) -> None:
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if _USE_POSIX:
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# We manually unlink to bypass all the "resource tracker"
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# nonsense meant for non-SC systems.
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shm_unlink(self._shm.name)
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class _Token(BaseModel):
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'''
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Internal represenation of a shared memory "token"
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which can be used to key a system wide post shm entry.
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'''
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class Config:
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frozen = True
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shm_name: str # this servers as a "key" value
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shm_first_index_name: str
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shm_last_index_name: str
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dtype_descr: tuple
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@property
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def dtype(self) -> np.dtype:
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return np.dtype(list(map(tuple, self.dtype_descr))).descr
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def as_msg(self):
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return self.dict()
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@classmethod
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def from_msg(cls, msg: dict) -> _Token:
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if isinstance(msg, _Token):
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return msg
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msg['dtype_descr'] = tuple(map(tuple, msg['dtype_descr']))
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return _Token(**msg)
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# TODO: this api?
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# _known_tokens = tractor.ActorVar('_shm_tokens', {})
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# _known_tokens = tractor.ContextStack('_known_tokens', )
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# _known_tokens = trio.RunVar('shms', {})
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# process-local store of keys to tokens
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_known_tokens = {}
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def get_shm_token(key: str) -> _Token:
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"""Convenience func to check if a token
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for the provided key is known by this process.
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"""
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return _known_tokens.get(key)
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def _make_token(
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key: str,
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dtype: Optional[np.dtype] = None,
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) -> _Token:
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'''
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Create a serializable token that can be used
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to access a shared array.
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'''
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dtype = base_iohlc_dtype if dtype is None else dtype
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return _Token(
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shm_name=key,
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shm_first_index_name=key + "_first",
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shm_last_index_name=key + "_last",
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dtype_descr=np.dtype(dtype).descr
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)
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class ShmArray:
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'''
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A shared memory ``numpy`` (compatible) array API.
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An underlying shared memory buffer is allocated based on
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a user specified ``numpy.ndarray``. This fixed size array
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can be read and written to by pushing data both onto the "front"
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or "back" of a set index range. The indexes for the "first" and
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"last" index are themselves stored in shared memory (accessed via
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``SharedInt`` interfaces) values such that multiple processes can
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interact with the same array using a synchronized-index.
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'''
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def __init__(
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self,
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shmarr: np.ndarray,
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first: SharedInt,
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last: SharedInt,
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shm: SharedMemory,
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# readonly: bool = True,
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) -> None:
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self._array = shmarr
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# indexes for first and last indices corresponding
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# to fille data
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self._first = first
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self._last = last
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self._len = len(shmarr)
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self._shm = shm
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self._post_init: bool = False
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# pushing data does not write the index (aka primary key)
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self._write_fields = list(shmarr.dtype.fields.keys())[1:]
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# TODO: ringbuf api?
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@property
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def _token(self) -> _Token:
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return _Token(
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shm_name=self._shm.name,
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shm_first_index_name=self._first._shm.name,
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shm_last_index_name=self._last._shm.name,
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dtype_descr=tuple(self._array.dtype.descr),
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)
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@property
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def token(self) -> dict:
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"""Shared memory token that can be serialized and used by
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another process to attach to this array.
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"""
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return self._token.as_msg()
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@property
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def index(self) -> int:
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return self._last.value % self._len
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@property
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def array(self) -> np.ndarray:
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'''
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Return an up-to-date ``np.ndarray`` view of the
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so-far-written data to the underlying shm buffer.
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'''
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a = self._array[self._first.value:self._last.value]
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# first, last = self._first.value, self._last.value
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# a = self._array[first:last]
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# TODO: eventually comment this once we've not seen it in the
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# wild in a long time..
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# XXX: race where first/last indexes cause a reader
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# to load an empty array..
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if len(a) == 0 and self._post_init:
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raise RuntimeError('Empty array race condition hit!?')
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# breakpoint()
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return a
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def last(
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self,
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length: int = 1,
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) -> np.ndarray:
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'''
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Return the last ``length``'s worth of ("row") entries from the
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array.
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'''
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return self.array[-length:]
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def push(
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self,
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data: np.ndarray,
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field_map: Optional[dict[str, str]] = None,
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prepend: bool = False,
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start: Optional[int] = None,
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) -> int:
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'''
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Ring buffer like "push" to append data
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into the buffer and return updated "last" index.
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NB: no actual ring logic yet to give a "loop around" on overflow
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condition, lel.
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'''
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length = len(data)
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index = start if start is not None else self._last.value
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if prepend:
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index = self._first.value - length
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if index < 0:
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raise ValueError(
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f'Array size of {self._len} was overrun during prepend.\n'
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f'You have passed {abs(index)} too many datums.'
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)
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end = index + length
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if field_map:
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src_names, dst_names = zip(*field_map.items())
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else:
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dst_names = src_names = self._write_fields
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try:
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self._array[
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list(dst_names)
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][index:end] = data[list(src_names)][:]
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# NOTE: there was a race here between updating
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# the first and last indices and when the next reader
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# tries to access ``.array`` (which due to the index
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# overlap will be empty). Pretty sure we've fixed it now
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# but leaving this here as a reminder.
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if prepend:
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assert index < self._first.value
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if index < self._first.value:
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self._first.value = index
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else:
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self._last.value = end
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self._post_init = True
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return end
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except ValueError as err:
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if field_map:
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raise
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# should raise if diff detected
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self.diff_err_fields(data)
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raise err
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def diff_err_fields(
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self,
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data: np.ndarray,
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) -> None:
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# reraise with any field discrepancy
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our_fields, their_fields = (
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set(self._array.dtype.fields),
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set(data.dtype.fields),
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)
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only_in_ours = our_fields - their_fields
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only_in_theirs = their_fields - our_fields
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if only_in_ours:
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raise TypeError(
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f"Input array is missing field(s): {only_in_ours}"
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)
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elif only_in_theirs:
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raise TypeError(
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f"Input array has unknown field(s): {only_in_theirs}"
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)
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def prepend(
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self,
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data: np.ndarray,
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) -> int:
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end = self.push(data, prepend=True)
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assert end
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def close(self) -> None:
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self._first._shm.close()
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self._last._shm.close()
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self._shm.close()
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def destroy(self) -> None:
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if _USE_POSIX:
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# We manually unlink to bypass all the "resource tracker"
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# nonsense meant for non-SC systems.
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shm_unlink(self._shm.name)
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self._first.destroy()
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self._last.destroy()
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def flush(self) -> None:
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# TODO: flush to storage backend like markestore?
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...
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def open_shm_array(
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key: Optional[str] = None,
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size: int = _default_size,
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dtype: Optional[np.dtype] = None,
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readonly: bool = False,
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) -> ShmArray:
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'''Open a memory shared ``numpy`` using the standard library.
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This call unlinks (aka permanently destroys) the buffer on teardown
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and thus should be used from the parent-most accessor (process).
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'''
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# create new shared mem segment for which we
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# have write permission
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a = np.zeros(size, dtype=dtype)
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a['index'] = np.arange(len(a))
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shm = SharedMemory(
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name=key,
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create=True,
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size=a.nbytes
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)
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array = np.ndarray(a.shape, dtype=a.dtype, buffer=shm.buf)
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array[:] = a[:]
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array.setflags(write=int(not readonly))
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token = _make_token(
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key=key,
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dtype=dtype
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)
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# create single entry arrays for storing an first and last indices
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first = SharedInt(
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shm=SharedMemory(
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name=token.shm_first_index_name,
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create=True,
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size=4, # std int
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)
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)
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last = SharedInt(
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shm=SharedMemory(
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name=token.shm_last_index_name,
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create=True,
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size=4, # std int
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)
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)
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# start the "real-time" updated section after 3-days worth of 1s
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# sampled OHLC. this allows appending up to a days worth from
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# tick/quote feeds before having to flush to a (tsdb) storage
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# backend, and looks something like,
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# -------------------------
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# | | i
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# _________________________
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# <-------------> <------->
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# history real-time
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#
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# Once fully "prepended", the history section will leave the
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# ``ShmArray._start.value: int = 0`` and the yet-to-be written
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# real-time section will start at ``ShmArray.index: int``.
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# this sets the index to 3/4 of the length of the buffer
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# leaving a "days worth of second samples" for the real-time
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# section.
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last.value = first.value = _rt_buffer_start
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shmarr = ShmArray(
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array,
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first,
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last,
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shm,
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)
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assert shmarr._token == token
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_known_tokens[key] = shmarr.token
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# "unlink" created shm on process teardown by
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# pushing teardown calls onto actor context stack
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tractor._actor._lifetime_stack.callback(shmarr.close)
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tractor._actor._lifetime_stack.callback(shmarr.destroy)
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return shmarr
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def attach_shm_array(
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token: tuple[str, str, tuple[str, str]],
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size: int = _default_size,
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readonly: bool = True,
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) -> ShmArray:
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'''
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Attach to an existing shared memory array previously
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created by another process using ``open_shared_array``.
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No new shared mem is allocated but wrapper types for read/write
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access are constructed.
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'''
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token = _Token.from_msg(token)
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key = token.shm_name
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if key in _known_tokens:
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assert _Token.from_msg(_known_tokens[key]) == token, "WTF"
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# attach to array buffer and view as per dtype
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shm = SharedMemory(name=key)
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shmarr = np.ndarray(
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(size,),
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dtype=token.dtype,
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buffer=shm.buf
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)
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shmarr.setflags(write=int(not readonly))
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first = SharedInt(
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shm=SharedMemory(
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name=token.shm_first_index_name,
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create=False,
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size=4, # std int
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),
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)
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last = SharedInt(
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shm=SharedMemory(
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name=token.shm_last_index_name,
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create=False,
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size=4, # std int
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),
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)
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# make sure we can read
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first.value
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sha = ShmArray(
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shmarr,
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first,
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last,
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shm,
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)
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# read test
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sha.array
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# Stash key -> token knowledge for future queries
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# via `maybe_opepn_shm_array()` but only after we know
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# we can attach.
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if key not in _known_tokens:
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_known_tokens[key] = token
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# "close" attached shm on process teardown
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tractor._actor._lifetime_stack.callback(sha.close)
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return sha
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def maybe_open_shm_array(
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key: str,
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dtype: Optional[np.dtype] = None,
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**kwargs,
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) -> tuple[ShmArray, bool]:
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'''
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Attempt to attach to a shared memory block using a "key" lookup
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to registered blocks in the users overall "system" registry
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(presumes you don't have the block's explicit token).
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This function is meant to solve the problem of discovering whether
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a shared array token has been allocated or discovered by the actor
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running in **this** process. Systems where multiple actors may seek
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to access a common block can use this function to attempt to acquire
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a token as discovered by the actors who have previously stored
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a "key" -> ``_Token`` map in an actor local (aka python global)
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variable.
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If you know the explicit ``_Token`` for your memory segment instead
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use ``attach_shm_array``.
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'''
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try:
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# see if we already know this key
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token = _known_tokens[key]
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return attach_shm_array(token=token, **kwargs), False
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except KeyError:
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log.warning(f"Could not find {key} in shms cache")
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if dtype:
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token = _make_token(key, dtype)
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try:
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return attach_shm_array(token=token, **kwargs), False
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except FileNotFoundError:
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log.warning(f"Could not attach to shm with token {token}")
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# This actor does not know about memory
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# associated with the provided "key".
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# Attempt to open a block and expect
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# to fail if a block has been allocated
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# on the OS by someone else.
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return open_shm_array(key=key, dtype=dtype, **kwargs), True
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def try_read(
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array: np.ndarray
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) -> Optional[np.ndarray]:
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'''
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Try to read the last row from a shared mem array or ``None``
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if the array read returns a zero-length array result.
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Can be used to check for backfilling race conditions where an array
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is currently being (re-)written by a writer actor but the reader is
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unaware and reads during the window where the first and last indexes
|
|
are being updated.
|
|
|
|
'''
|
|
try:
|
|
return array[-1]
|
|
except IndexError:
|
|
# XXX: race condition with backfilling shm.
|
|
#
|
|
# the underlying issue is that a backfill (aka prepend) and subsequent
|
|
# shm array first/last index update could result in an empty array
|
|
# read here since the indices may be updated in such a way that
|
|
# a read delivers an empty array (though it seems like we
|
|
# *should* be able to prevent that?). also, as and alt and
|
|
# something we need anyway, maybe there should be some kind of
|
|
# signal that a prepend is taking place and this consumer can
|
|
# respond (eg. redrawing graphics) accordingly.
|
|
|
|
# the array read was emtpy
|
|
return None
|