Add MemoryRecordStore (#14919)

src/prefect/records/__init__.py

@@ -1 +1 @@
-from .store import RecordStore
+from .base import RecordStore

src/prefect/records/base.py

@@ -0,0 +1,167 @@
+import os
+import socket
+import threading
+from contextlib import contextmanager
+from dataclasses import dataclass
+from typing import Optional
+
+from prefect.results import BaseResult
+
+
+class RecordStore:
+    def read(self, key: str):
+        raise NotImplementedError
+
+    def write(self, key: str, value: dict):
+        raise NotImplementedError
+
+    def exists(self, key: str) -> bool:
+        return False
+
+    def acquire_lock(
+        self,
+        key: str,
+        holder: Optional[str] = None,
+        acquire_timeout: Optional[float] = None,
+        hold_timeout: Optional[float] = None,
+    ) -> bool:
+        """
+        Acquire a lock for a transaction record with the given key. Will block other
+        actors from updating this transaction record until the lock is
+        released.
+
+        Args:
+            key: Unique identifier for the transaction record.
+            holder: Unique identifier for the holder of the lock. If not provided,
+                a default holder based on the current host, process, and thread will
+                be used.
+            acquire_timeout: Max number of seconds to wait for the record to become
+                available if it is locked while attempting to acquire a lock. Pass 0
+                to attempt to acquire a lock without waiting. Blocks indefinitely by
+                default.
+            hold_timeout: Max number of seconds to hold the lock for. Holds the lock
+                indefinitely by default.
+
+        Returns:
+            bool: True if the lock was successfully acquired; False otherwise.
+        """
+        raise NotImplementedError
+
+    def release_lock(self, key: str, holder: Optional[str] = None):
+        """
+        Releases the lock on the corresponding transaction record.
+
+        Args:
+            key: Unique identifier for the transaction record.
+            holder: Unique identifier for the holder of the lock. Must match the
+                holder provided when acquiring the lock.
+        """
+        raise NotImplementedError
+
+    def is_locked(self, key: str) -> bool:
+        """
+        Simple check to see if the corresponding record is currently locked.
+
+        Args:
+            key: Unique identifier for the transaction record.
+
+        Returns:
+            True is the record is locked; False otherwise.
+        """
+        raise NotImplementedError
+
+    def is_lock_holder(self, key: str, holder: Optional[str] = None) -> bool:
+        """
+        Check if the current holder is the lock holder for the transaction record.
+
+        Args:
+            key: Unique identifier for the transaction record.
+            holder: Unique identifier for the holder of the lock. If not provided,
+                a default holder based on the current host, process, and thread will
+                be used.
+
+        Returns:
+            bool: True if the current holder is the lock holder; False otherwise.
+        """
+        raise NotImplementedError
+
+    def wait_for_lock(self, key: str, timeout: Optional[float] = None) -> bool:
+        """
+        Wait for the corresponding transaction record to become free.
+
+        Args:
+            key: Unique identifier for the transaction record.
+            timeout: Maximum time to wait. None means to wait indefinitely.
+
+        Returns:
+            bool: True if the lock becomes free within the timeout; False
+                otherwise.
+        """
+        ...
+
+    @staticmethod
+    def generate_default_holder() -> str:
+        """
+        Generate a default holder string using hostname, PID, and thread ID.
+
+        Returns:
+            str: A unique identifier string.
+        """
+        hostname = socket.gethostname()
+        pid = os.getpid()
+        thread_name = threading.current_thread().name
+        thread_id = threading.get_ident()
+        return f"{hostname}:{pid}:{thread_id}:{thread_name}"
+
+    @contextmanager
+    def lock(
+        self,
+        key: str,
+        holder: Optional[str] = None,
+        acquire_timeout: Optional[float] = None,
+        hold_timeout: Optional[float] = None,
+    ):
+        """
+        Context manager to lock the transaction record during the execution
+        of the nested code block.
+
+        Args:
+            key: Unique identifier for the transaction record.
+            holder: Unique identifier for the holder of the lock. If not provided,
+                a default holder based on the current host, process, and thread will
+                be used.
+            acquire_timeout: Max number of seconds to wait for the record to become
+                available if it is locked while attempting to acquire a lock. Pass 0
+                to attempt to acquire a lock without waiting. Blocks indefinitely by
+                default.
+            hold_timeout: Max number of seconds to hold the lock for. Holds the lock
+                indefinitely by default.
+
+        Example:
+            Hold a lock while during an operation:
+                ```python
+                    with TransactionRecord(key="my-transaction-record-key").lock():
+                        do_stuff()
+                ```
+        """
+        self.acquire_lock(
+            key=key,
+            holder=holder,
+            acquire_timeout=acquire_timeout,
+            hold_timeout=hold_timeout,
+        )
+
+        try:
+            yield
+        finally:
+            self.release_lock(key=key, holder=holder)
+
+
+@dataclass
+class TransactionRecord:
+    """
+    A dataclass representation of a transaction record.
+    """
+
+    key: str
+    result: Optional[BaseResult] = None

src/prefect/records/memory.py

@@ -0,0 +1,165 @@
+import threading
+from typing import Dict, Optional, TypedDict
+
+from prefect.results import BaseResult
+
+from .base import RecordStore, TransactionRecord
+
+
+class _LockInfo(TypedDict):
+    """
+    A dictionary containing information about a lock.
+
+    Attributes:
+        holder: The holder of the lock.
+        lock: The lock object.
+        expiration_timer: The timer for the lock expiration
+    """
+
+    holder: str
+    lock: threading.Lock
+    expiration_timer: Optional[threading.Timer]
+
+
+class MemoryRecordStore(RecordStore):
+    """
+    A record store that stores data in memory.
+    """
+
+    _instance = None
+
+    def __new__(cls, *args, **kwargs):
+        if cls._instance is None:
+            cls._instance = super().__new__(cls)
+        return cls._instance
+
+    def __init__(self):
+        self._locks_dict_lock = threading.Lock()
+        self._locks: Dict[str, _LockInfo] = {}
+        self._records: Dict[str, TransactionRecord] = {}
+
+    def read(self, key: str) -> Optional[TransactionRecord]:
+        return self._records.get(key)
+
+    def write(self, key: str, value: BaseResult, holder: Optional[str] = None) -> None:
+        holder = holder or self.generate_default_holder()
+
+        with self._locks_dict_lock:
+            if self.is_locked(key) and not self.is_lock_holder(key, holder):
+                raise ValueError(
+                    f"Cannot write to transaction with key {key} because it is locked by another holder."
+                )
+        self._records[key] = TransactionRecord(key=key, result=value)
+
+    def exists(self, key: str) -> bool:
+        return key in self._records
+
+    def _expire_lock(self, key: str):
+        """
+        Expire the lock for the given key.
+
+        Used as a callback for the expiration timer of a lock.
+
+        Args:
+            key: The key of the lock to expire.
+        """
+        with self._locks_dict_lock:
+            if key in self._locks:
+                lock_info = self._locks[key]
+                if lock_info["lock"].locked():
+                    lock_info["lock"].release()
+                if lock_info["expiration_timer"]:
+                    lock_info["expiration_timer"].cancel()
+                del self._locks[key]
+
+    def acquire_lock(
+        self,
+        key: str,
+        holder: Optional[str] = None,
+        acquire_timeout: Optional[float] = None,
+        hold_timeout: Optional[float] = None,
+    ) -> bool:
+        holder = holder or self.generate_default_holder()
+        with self._locks_dict_lock:
+            if key not in self._locks:
+                lock = threading.Lock()
+                lock.acquire()
+                expiration_timer = None
+                if hold_timeout is not None:
+                    expiration_timer = threading.Timer(
+                        hold_timeout, self._expire_lock, args=(key,)
+                    )
+                    expiration_timer.start()
+                self._locks[key] = _LockInfo(
+                    holder=holder, lock=lock, expiration_timer=expiration_timer
+                )
+                return True
+            elif self._locks[key]["holder"] == holder:
+                return True
+            else:
+                existing_lock_info = self._locks[key]
+
+        if acquire_timeout is not None:
+            existing_lock_acquired = existing_lock_info["lock"].acquire(
+                timeout=acquire_timeout
+            )
+        else:
+            existing_lock_acquired = existing_lock_info["lock"].acquire()
+
+        if existing_lock_acquired:
+            with self._locks_dict_lock:
+                if (
+                    expiration_timer := existing_lock_info["expiration_timer"]
+                ) is not None:
+                    expiration_timer.cancel()
+                expiration_timer = None
+                if hold_timeout is not None:
+                    expiration_timer = threading.Timer(
+                        hold_timeout, self._expire_lock, args=(key,)
+                    )
+                    expiration_timer.start()
+                self._locks[key] = _LockInfo(
+                    holder=holder,
+                    lock=existing_lock_info["lock"],
+                    expiration_timer=expiration_timer,
+                )
+            return True
+        return False
+
+    def release_lock(self, key: str, holder: Optional[str] = None) -> None:
+        holder = holder or self.generate_default_holder()
+        with self._locks_dict_lock:
+            if key in self._locks and self._locks[key]["holder"] == holder:
+                if (
+                    expiration_timer := self._locks[key]["expiration_timer"]
+                ) is not None:
+                    expiration_timer.cancel()
+                self._locks[key]["lock"].release()
+                del self._locks[key]
+            else:
+                raise ValueError(
+                    f"No lock held by {holder} for transaction with key {key}"
+                )
+
+    def is_locked(self, key: str) -> bool:
+        return key in self._locks and self._locks[key]["lock"].locked()
+
+    def is_lock_holder(self, key: str, holder: Optional[str] = None) -> bool:
+        holder = holder or self.generate_default_holder()
+        lock_info = self._locks.get(key)
+        return (
+            lock_info is not None
+            and lock_info["lock"].locked()
+            and lock_info["holder"] == holder
+        )
+
+    def wait_for_lock(self, key: str, timeout: Optional[float] = None) -> bool:
+        if lock := self._locks.get(key, {}).get("lock"):
+            if timeout is not None:
+                lock_acquired = lock.acquire(timeout=timeout)
+            else:
+                lock_acquired = lock.acquire()
+            if lock_acquired:
+                lock.release()
+            return lock_acquired
+        return True

src/prefect/records/result_store.py

@@ -6,7 +6,7 @@
 from prefect.results import BaseResult, PersistedResult, ResultFactory
 from prefect.utilities.asyncutils import run_coro_as_sync
 
-from .store import RecordStore
+from .base import RecordStore
 
 
 @dataclass