chore: Introducing Synchronizer protocol & streaming implementation

ldclient/impl/datasourcev2/__init__.py

@@ -1,6 +1,77 @@
 """
 This module houses FDv2 types and implementations of synchronizers and
 initializers for the datasystem.
+
+All types and implementations in this module are considered internal
+and are not part of the public API of the LaunchDarkly Python SDK.
+They are subject to change without notice and should not be used directly
+by users of the SDK.
+
+You have been warned.
 """
 
+from abc import abstractmethod
+from dataclasses import dataclass
+from typing import Generator, Iterable, Mapping, Optional, Protocol, Tuple
+
+from ldclient.impl.datasystem.protocolv2 import ChangeSet, Selector
+from ldclient.impl.util import _Result
+from ldclient.interfaces import DataSourceErrorInfo, DataSourceState
+
+PollingResult = _Result[Tuple[ChangeSet, Mapping], str]
+
+
+class PollingRequester(Protocol):  # pylint: disable=too-few-public-methods
+    """
+    PollingRequester allows PollingDataSource to delegate fetching data to
+    another component.
+
+    This is useful for testing the PollingDataSource without needing to set up
+    a test HTTP server.
+    """
+
+    @abstractmethod
+    def fetch(self, selector: Optional[Selector]) -> PollingResult:
+        """
+        Fetches the data for the given selector.
+        Returns a Result containing a tuple of ChangeSet and any request headers,
+        or an error if the data could not be retrieved.
+        """
+        raise NotImplementedError
+
+
+@dataclass(frozen=True)
+class Update:
+    """
+    Update represents the results of a synchronizer's ongoing sync
+    method.
+    """
+
+    state: DataSourceState
+    change_set: Optional[ChangeSet] = None
+    error: Optional[DataSourceErrorInfo] = None
+    revert_to_fdv1: bool = False
+    environment_id: Optional[str] = None
+
+
+class Synchronizer(Protocol):  # pylint: disable=too-few-public-methods
+    """
+    Synchronizer represents a component capable of synchronizing data from an external
+    data source, such as a streaming or polling API.
+
+    It is responsible for yielding Update objects that represent the current state
+    of the data source, including any changes that have occurred since the last
+    synchronization.
+    """
+
+    @abstractmethod
+    def sync(self) -> Generator[Update, None, None]:
+        """
+        sync should begin the synchronization process for the data source, yielding
+        Update objects until the connection is closed or an unrecoverable error
+        occurs.
+        """
+        raise NotImplementedError
+
+
 __all__: list[str] = []

ldclient/impl/datasourcev2/polling.py

@@ -1,16 +1,16 @@
 """
-Default implementation of the polling synchronizer and initializer.
+This module contains the implementations of a polling synchronizer and
+initializer, along with any required supporting classes and protocols.
 """
 
 import json
-from abc import abstractmethod
 from collections import namedtuple
-from collections.abc import Mapping
-from typing import Optional, Protocol, Tuple
+from typing import Iterable, Optional
 from urllib import parse
 
 import urllib3
 
+from ldclient.impl.datasourcev2 import PollingRequester, PollingResult, Update
 from ldclient.impl.datasystem.protocolv2 import (
     Basis,
     ChangeSet,
@@ -38,27 +38,6 @@
 
 POLLING_ENDPOINT = "/sdk/poll"
 
-PollingResult = _Result[Tuple[ChangeSet, Mapping], str]
-
-
-class PollingRequester(Protocol):  # pylint: disable=too-few-public-methods
-    """
-    PollingRequester allows PollingDataSource to delegate fetching data to
-    another component.
-
-    This is useful for testing the PollingDataSource without needing to set up
-    a test HTTP server.
-    """
-
-    @abstractmethod
-    def fetch(self, selector: Optional[Selector]) -> PollingResult:
-        """
-        Fetches the data for the given selector.
-        Returns a Result containing a tuple of ChangeSet and any request headers,
-        or an error if the data could not be retrieved.
-        """
-        raise NotImplementedError
-
 
 CacheEntry = namedtuple("CacheEntry", ["data", "etag"])