Add prepend support to shm system

piker/data/_sharedmem.py

@@ -17,11 +17,10 @@
 """
 NumPy compatible shared memory buffers for real-time FSP.
 """
-from typing import List
 from dataclasses import dataclass, asdict
 from sys import byteorder
-from typing import Tuple, Optional
+from typing import List, Tuple, Optional
-from multiprocessing import shared_memory
+from multiprocessing.shared_memory import SharedMemory, _USE_POSIX
 from multiprocessing import resource_tracker as mantracker
 from _posixshmem import shm_unlink
 
@@ -29,7 +28,7 @@ import tractor
 import numpy as np
 
 from ..log import get_logger
-from ._source import base_ohlc_dtype
+from ._source import base_ohlc_dtype, base_iohlc_dtype
 
 
 log = get_logger(__name__)
@@ -58,17 +57,15 @@ mantracker.getfd = mantracker._resource_tracker.getfd
 
 
 class SharedInt:
+    """Wrapper around a single entry shared memory array which
+    holds an ``int`` value used as an index counter.
+
+    """
     def __init__(
         self,
-        token: str,
+        shm: SharedMemory,
-        create: bool = False,
     ) -> None:
-        # create a single entry array for storing an index counter
+        self._shm = shm
-        self._shm = shared_memory.SharedMemory(
-            name=token,
-            create=create,
-            size=4,  # std int
-        )
 
     @property
     def value(self) -> int:
@@ -79,7 +76,7 @@ class SharedInt:
         self._shm.buf[:] = value.to_bytes(4, byteorder)
 
     def destroy(self) -> None:
-        if shared_memory._USE_POSIX:
+        if _USE_POSIX:
             # We manually unlink to bypass all the "resource tracker"
             # nonsense meant for non-SC systems.
             shm_unlink(self._shm.name)
@@ -91,7 +88,8 @@ class _Token:
     which can be used to key a system wide post shm entry.
     """
     shm_name: str  # this servers as a "key" value
-    shm_counter_name: str
+    shm_first_index_name: str
+    shm_last_index_name: str
     dtype_descr: List[Tuple[str]]
 
     def __post_init__(self):
@@ -130,27 +128,47 @@ def _make_token(
     """Create a serializable token that can be used
     to access a shared array.
     """
-    dtype = base_ohlc_dtype if dtype is None else dtype
+    dtype = base_iohlc_dtype if dtype is None else dtype
     return _Token(
         key,
-        key + "_counter",
+        key + "_first",
+        key + "_last",
         np.dtype(dtype).descr
     )
 
 
 class ShmArray:
+    """A shared memory ``numpy`` (compatible) array API.
+
+    An underlying shared memory buffer is allocated based on
+    a user specified ``numpy.ndarray``. This fixed size array
+    can be read and written to by pushing data both onto the "front"
+    or "back" of a set index range. The indexes for the "first" and
+    "last" index are themselves stored in shared memory (accessed via
+    ``SharedInt`` interfaces) values such that multiple processes can
+    interact with the same array using a synchronized-index.
+
+    """
     def __init__(
         self,
         shmarr: np.ndarray,
-        counter: SharedInt,
+        first: SharedInt,
-        shm: shared_memory.SharedMemory,
+        last: SharedInt,
-        readonly: bool = True,
+        shm: SharedMemory,
+        # readonly: bool = True,
     ) -> None:
         self._array = shmarr
-        self._i = counter
+
+        # indexes for first and last indices corresponding
+        # to fille data
+        self._first = first
+        self._last = last
+
         self._len = len(shmarr)
         self._shm = shm
-        self._readonly = readonly
+
+        # pushing data does not write the index (aka primary key)
+        self._write_fields = list(shmarr.dtype.fields.keys())[1:]
 
     # TODO: ringbuf api?
 
@@ -158,24 +176,25 @@ class ShmArray:
     def _token(self) -> _Token:
         return _Token(
             self._shm.name,
-            self._i._shm.name,
+            self._first._shm.name,
+            self._last._shm.name,
             self._array.dtype.descr,
         )
 
     @property
     def token(self) -> dict:
-        """Shared memory token that can be serialized
+        """Shared memory token that can be serialized and used by
-        and used by another process to attach to this array.
+        another process to attach to this array.
         """
         return self._token.as_msg()
 
     @property
     def index(self) -> int:
-        return self._i.value % self._len
+        return self._last.value % self._len
 
     @property
     def array(self) -> np.ndarray:
-        return self._array[:self._i.value]
+        return self._array[self._first.value:self._last.value]
 
     def last(
         self,
@@ -186,19 +205,39 @@ class ShmArray:
     def push(
         self,
         data: np.ndarray,
+        prepend: bool = False,
     ) -> int:
         """Ring buffer like "push" to append data
-        into the buffer and return updated index.
+        into the buffer and return updated "last" index.
         """
         length = len(data)
-        # TODO: use .index for actual ring logic?
+
-        index = self._i.value
+        if prepend:
+            index = self._first.value - length
+        else:
+            index = self._last.value
+
         end = index + length
+
+        fields = self._write_fields
+
         try:
-            self._array[index:end] = data[:]
+            self._array[fields][index:end] = data[fields][:]
-            self._i.value = end
+            if prepend:
+                self._first.value = index
+            else:
+                self._last.value = end
             return end
         except ValueError as err:
+            # shoudl raise if diff detected
+            self.diff_err_fields(data)
+
+            raise err
+
+    def diff_err_fields(
+        self,
+        data: np.ndarray,
+    ) -> None:
         # reraise with any field discrepancy
         our_fields, their_fields = (
             set(self._array.dtype.fields),
@@ -216,32 +255,40 @@ class ShmArray:
             raise TypeError(
                 f"Input array has unknown field(s): {only_in_theirs}"
             )
-            else:
+
-                raise err
+    def prepend(
+        self,
+        data: np.ndarray,
+    ) -> int:
+        end = self.push(data, prepend=True)
+        assert end
 
     def close(self) -> None:
-        self._i._shm.close()
+        self._first._shm.close()
+        self._last._shm.close()
         self._shm.close()
 
     def destroy(self) -> None:
-        if shared_memory._USE_POSIX:
+        if _USE_POSIX:
             # We manually unlink to bypass all the "resource tracker"
             # nonsense meant for non-SC systems.
             shm_unlink(self._shm.name)
-        self._i.destroy()
+
+        self._first.destroy()
+        self._last.destroy()
 
     def flush(self) -> None:
         # TODO: flush to storage backend like markestore?
         ...
 
 
-_lotsa_5s = int(5 * 60 * 60 * 10 / 5)
+# how  much is probably dependent on lifestyle
-
+_secs_in_day = int(60 * 60 * 12)
+_default_size = 2 * _secs_in_day
 
 def open_shm_array(
     key: Optional[str] = None,
-    # approx number of 5s bars in a "day" x2
+    size: int = _default_size,
-    size: int = _lotsa_5s,
     dtype: Optional[np.dtype] = None,
     readonly: bool = False,
 ) -> ShmArray:
@@ -253,7 +300,9 @@ def open_shm_array(
     # create new shared mem segment for which we
     # have write permission
     a = np.zeros(size, dtype=dtype)
-    shm = shared_memory.SharedMemory(
+    a['index'] = np.arange(len(a))
+
+    shm = SharedMemory(
         name=key,
         create=True,
         size=a.nbytes
@@ -267,17 +316,30 @@ def open_shm_array(
         dtype=dtype
     )
 
-    counter = SharedInt(
+    # create single entry arrays for storing an first and last indices
-        token=token.shm_counter_name,
+    first = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_first_index_name,
             create=True,
+            size=4,  # std int
         )
-    counter.value = 0
+    )
+
+    last = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_last_index_name,
+            create=True,
+            size=4,  # std int
+        )
+    )
+
+    last.value = first.value = int(_secs_in_day)
 
     shmarr = ShmArray(
         array,
-        counter,
+        first,
+        last,
         shm,
-        readonly=readonly,
     )
 
     assert shmarr._token == token
@@ -293,18 +355,23 @@ def open_shm_array(
 
 def attach_shm_array(
     token: Tuple[str, str, Tuple[str, str]],
-    size: int = _lotsa_5s,
+    size: int = _default_size,
     readonly: bool = True,
 ) -> ShmArray:
-    """Load and attach to an existing shared memory array previously
+    """Attach to an existing shared memory array previously
     created by another process using ``open_shared_array``.
+
+    No new shared mem is allocated but wrapper types for read/write
+    access are constructed.
     """
     token = _Token.from_msg(token)
     key = token.shm_name
+
     if key in _known_tokens:
         assert _known_tokens[key] == token, "WTF"
 
-    shm = shared_memory.SharedMemory(name=key)
+    # attach to array buffer and view as per dtype
+    shm = SharedMemory(name=key)
     shmarr = np.ndarray(
         (size,),
         dtype=token.dtype_descr,
@@ -312,15 +379,29 @@ def attach_shm_array(
     )
     shmarr.setflags(write=int(not readonly))
 
-    counter = SharedInt(token=token.shm_counter_name)
+    first = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_first_index_name,
+            create=False,
+            size=4,  # std int
+        ),
+    )
+    last = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_last_index_name,
+            create=False,
+            size=4,  # std int
+        ),
+    )
+
     # make sure we can read
-    counter.value
+    first.value
 
     sha = ShmArray(
         shmarr,
-        counter,
+        first,
+        last,
         shm,
-        readonly=readonly,
     )
     # read test
     sha.array