chore: Initial structure and implementation of FDv2 datasystem

ldclient/client.py

@@ -30,6 +30,8 @@
     DataStoreStatusProviderImpl,
     DataStoreUpdateSinkImpl
 )
+from ldclient.impl.datasystem import DataAvailability, DataSystem
+from ldclient.impl.datasystem.fdv2 import FDv2
 from ldclient.impl.evaluator import Evaluator, error_reason
 from ldclient.impl.events.diagnostics import (
     _DiagnosticAccumulator,
@@ -249,14 +251,19 @@ def __start_up(self, start_wait: float):
         self.__hooks_lock = ReadWriteLock()
         self.__hooks = self._config.hooks + plugin_hooks  # type: List[Hook]
 
-        # Initialize data system (FDv1) to encapsulate v1 data plumbing
-        from ldclient.impl.datasystem.fdv1 import (  # local import to avoid circular dependency
-            FDv1
-        )
+        datasystem_config = self._config.datasystem_config
+        if datasystem_config is None:
+            # Initialize data system (FDv1) to encapsulate v1 data plumbing
+            from ldclient.impl.datasystem.fdv1 import (  # local import to avoid circular dependency
+                FDv1
+            )
+
+            self._data_system: DataSystem = FDv1(self._config)
+        else:
+            self._data_system = FDv2(datasystem_config, disabled=self._config.offline)
 
-        self._data_system = FDv1(self._config)
         # Provide flag evaluation function for value-change tracking
-        self._data_system.set_flag_value_eval_fn(
+        self._data_system.set_flag_value_eval_fn(  # type: ignore
             lambda key, context: self.variation(key, context, None)
         )
         # Expose providers and store from data system
@@ -265,7 +272,7 @@ def __start_up(self, start_wait: float):
             self._data_system.data_source_status_provider
         )
         self.__flag_tracker = self._data_system.flag_tracker
-        self._store = self._data_system.store  # type: FeatureStore
+        self._store: FeatureStore = self._data_system.store  # type: ignore
 
         big_segment_store_manager = BigSegmentStoreManager(self._config.big_segments)
         self.__big_segment_store_manager = big_segment_store_manager
@@ -286,7 +293,7 @@ def __start_up(self, start_wait: float):
         diagnostic_accumulator = self._set_event_processor(self._config)
 
         # Pass diagnostic accumulator to data system for streaming metrics
-        self._data_system.set_diagnostic_accumulator(diagnostic_accumulator)
+        self._data_system.set_diagnostic_accumulator(diagnostic_accumulator)  # type: ignore
 
         self.__register_plugins(environment_metadata)
 
@@ -475,11 +482,7 @@ def is_initialized(self) -> bool:
         if self.is_offline() or self._config.use_ldd:
             return True
 
-        return (
-            self._data_system._update_processor.initialized()
-            if self._data_system._update_processor
-            else False
-        )
+        return self._data_system.data_availability.at_least(DataAvailability.CACHED)
 
     def flush(self):
         """Flushes all pending analytics events.

ldclient/config.py

@@ -4,11 +4,13 @@
 Note that the same class can also be imported from the ``ldclient.client`` submodule.
 """
 
+from dataclasses import dataclass
 from threading import Event
-from typing import Callable, List, Optional, Set
+from typing import Callable, List, Optional, Set, TypeVar
 
 from ldclient.feature_store import InMemoryFeatureStore
 from ldclient.hook import Hook
+from ldclient.impl.datasystem import Initializer, Synchronizer
 from ldclient.impl.util import (
     log,
     validate_application_info,
@@ -152,6 +154,32 @@ def disable_ssl_verification(self) -> bool:
         return self.__disable_ssl_verification
 
 
+T = TypeVar("T")
+
+Builder = Callable[[], T]
+
+
+@dataclass(frozen=True)
+class DataSystemConfig:
+    """
+    Configuration for LaunchDarkly's data acquisition strategy.
+    """
+
+    initializers: Optional[List[Builder[Initializer]]]
+    """The initializers for the data system."""
+
+    primary_synchronizer: Builder[Synchronizer]
+    """The primary synchronizer for the data system."""
+
+    secondary_synchronizer: Optional[Builder[Synchronizer]] = None
+    """The secondary synchronizers for the data system."""
+
+    # TODO(fdv2): Implement this synchronizer up and hook it up everywhere.
+    # TODO(fdv2): Remove this when FDv2 is fully launched
+    fdv1_fallback_synchronizer: Optional[Builder[Synchronizer]] = None
+    """An optional fallback synchronizer that will read from FDv1"""
+
+
 class Config:
     """Advanced configuration options for the SDK client.
 
@@ -194,6 +222,7 @@ def __init__(
         enable_event_compression: bool = False,
         omit_anonymous_contexts: bool = False,
         payload_filter_key: Optional[str] = None,
+        datasystem_config: Optional[DataSystemConfig] = None,
     ):
         """
         :param sdk_key: The SDK key for your LaunchDarkly account. This is always required.
@@ -264,6 +293,7 @@ def __init__(
         :param enable_event_compression: Whether or not to enable GZIP compression for outgoing events.
         :param omit_anonymous_contexts: Sets whether anonymous contexts should be omitted from index and identify events.
         :param payload_filter_key: The payload filter is used to selectively limited the flags and segments delivered in the data source payload.
+        :param datasystem_config: Configuration for the upcoming enhanced data system design. This is experimental and should not be set without direction from LaunchDarkly support.
         """
         self.__sdk_key = validate_sdk_key_format(sdk_key, log)
 
@@ -303,6 +333,7 @@ def __init__(
         self.__payload_filter_key = payload_filter_key
         self._data_source_update_sink: Optional[DataSourceUpdateSink] = None
         self._instance_id: Optional[str] = None
+        self._datasystem_config = datasystem_config
 
     def copy_with_new_sdk_key(self, new_sdk_key: str) -> 'Config':
         """Returns a new ``Config`` instance that is the same as this one, except for having a different SDK key.
@@ -546,6 +577,15 @@ def data_source_update_sink(self) -> Optional[DataSourceUpdateSink]:
         """
         return self._data_source_update_sink
 
+    @property
+    def datasystem_config(self) -> Optional[DataSystemConfig]:
+        """
+        Configuration for the upcoming enhanced data system design. This is
+        experimental and should not be set without direction from LaunchDarkly
+        support.
+        """
+        return self._datasystem_config
+
     def _validate(self):
         if self.offline is False and self.sdk_key == '':
             log.warning("Missing or blank SDK key")

ldclient/impl/datasourcev2/polling.py

@@ -90,6 +90,7 @@ def __init__(
             "ldclient.datasource.polling", poll_interval, 0, self._poll
         )
 
+    @property
     def name(self) -> str:
         """Returns the name of the initializer."""
         return "PollingDataSourceV2"

ldclient/impl/datasourcev2/status.py

@@ -0,0 +1,57 @@
+import time
+from typing import Callable, Optional
+
+from ldclient.impl.listeners import Listeners
+from ldclient.impl.rwlock import ReadWriteLock
+from ldclient.interfaces import (
+    DataSourceErrorInfo,
+    DataSourceState,
+    DataSourceStatus,
+    DataSourceStatusProvider
+)
+
+
+class DataSourceStatusProviderImpl(DataSourceStatusProvider):
+    def __init__(self, listeners: Listeners):
+        self.__listeners = listeners
+        self.__status = DataSourceStatus(DataSourceState.INITIALIZING, 0, None)
+        self.__lock = ReadWriteLock()
+
+    @property
+    def status(self) -> DataSourceStatus:
+        self.__lock.rlock()
+        status = self.__status
+        self.__lock.runlock()
+
+        return status
+
+    def update_status(self, new_state: DataSourceState, new_error: Optional[DataSourceErrorInfo]):
+        status_to_broadcast = None
+
+        try:
+            self.__lock.lock()
+            old_status = self.__status
+
+            if new_state == DataSourceState.INTERRUPTED and old_status.state == DataSourceState.INITIALIZING:
+                new_state = DataSourceState.INITIALIZING
+
+            if new_state == old_status.state and new_error is None:
+                return
+
+            new_since = self.__status.since if new_state == self.__status.state else time.time()
+            new_error = self.__status.error if new_error is None else new_error
+
+            self.__status = DataSourceStatus(new_state, new_since, new_error)
+
+            status_to_broadcast = self.__status
+        finally:
+            self.__lock.unlock()
+
+        if status_to_broadcast is not None:
+            self.__listeners.notify(status_to_broadcast)
+
+    def add_listener(self, listener: Callable[[DataSourceStatus], None]):
+        self.__listeners.add(listener)
+
+    def remove_listener(self, listener: Callable[[DataSourceStatus], None]):
+        self.__listeners.remove(listener)

ldclient/impl/datasourcev2/streaming.py

@@ -129,6 +129,13 @@ def __init__(
         self._config = config
         self._sse: Optional[SSEClient] = None
 
+    @property
+    def name(self) -> str:
+        """
+        Returns the name of the synchronizer, which is used for logging and debugging.
+        """
+        return "streaming"
+
     def sync(self) -> Generator[Update, None, None]:
         """
         sync should begin the synchronization process for the data source, yielding

ldclient/impl/datastore/status.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from copy import copy
-from typing import TYPE_CHECKING, Callable
+from typing import TYPE_CHECKING, Callable, Protocol
 
 from ldclient.impl.listeners import Listeners
 from ldclient.impl.rwlock import ReadWriteLock

ldclient/impl/datasystem/__init__.py

@@ -156,6 +156,14 @@ class Initializer(Protocol):  # pylint: disable=too-few-public-methods
     as new changes occur.
     """
 
+    @property
+    @abstractmethod
+    def name(self) -> str:
+        """
+        Returns the name of the initializer, which is used for logging and debugging.
+        """
+        raise NotImplementedError
+
     @abstractmethod
     def fetch(self) -> BasisResult:
         """
@@ -188,6 +196,13 @@ class Synchronizer(Protocol):  # pylint: disable=too-few-public-methods
     of the data source, including any changes that have occurred since the last
     synchronization.
     """
+    @property
+    @abstractmethod
+    def name(self) -> str:
+        """
+        Returns the name of the synchronizer, which is used for logging and debugging.
+        """
+        raise NotImplementedError
 
     @abstractmethod
     def sync(self) -> Generator[Update, None, None]:

ldclient/impl/datasystem/config.py

@@ -2,10 +2,10 @@
 Configuration for LaunchDarkly's data acquisition strategy.
 """
 
-from dataclasses import dataclass
 from typing import Callable, List, Optional, TypeVar
 
 from ldclient.config import Config as LDConfig
+from ldclient.config import DataSystemConfig
 from ldclient.impl.datasourcev2.polling import (
     PollingDataSource,
     PollingDataSourceBuilder,
@@ -22,22 +22,6 @@
 Builder = Callable[[], T]
 
 
-@dataclass(frozen=True)
-class Config:
-    """
-    Configuration for LaunchDarkly's data acquisition strategy.
-    """
-
-    initializers: Optional[List[Builder[Initializer]]]
-    """The initializers for the data system."""
-
-    primary_synchronizer: Builder[Synchronizer]
-    """The primary synchronizer for the data system."""
-
-    secondary_synchronizer: Optional[Builder[Synchronizer]]
-    """The secondary synchronizers for the data system."""
-
-
 class ConfigBuilder:  # pylint: disable=too-few-public-methods
     """
     Builder for the data system configuration.
@@ -47,7 +31,7 @@ class ConfigBuilder:  # pylint: disable=too-few-public-methods
     _primary_synchronizer: Optional[Builder[Synchronizer]] = None
     _secondary_synchronizer: Optional[Builder[Synchronizer]] = None
 
-    def initializers(self, initializers: List[Builder[Initializer]]) -> "ConfigBuilder":
+    def initializers(self, initializers: Optional[List[Builder[Initializer]]]) -> "ConfigBuilder":
         """
         Sets the initializers for the data system.
         """
@@ -66,14 +50,14 @@ def synchronizers(
         self._secondary_synchronizer = secondary
         return self
 
-    def build(self) -> Config:
+    def build(self) -> DataSystemConfig:
         """
         Builds the data system configuration.
         """
         if self._primary_synchronizer is None:
             raise ValueError("Primary synchronizer must be set")
 
-        return Config(
+        return DataSystemConfig(
             initializers=self._initializers,
             primary_synchronizer=self._primary_synchronizer,
             secondary_synchronizer=self._secondary_synchronizer,
@@ -144,7 +128,7 @@ def polling(config: LDConfig) -> ConfigBuilder:
     streaming, but may be necessary in some network environments.
     """
 
-    polling_builder = __polling_ds_builder(config)
+    polling_builder: Builder[Synchronizer] = __polling_ds_builder(config)
 
     builder = ConfigBuilder()
     builder.synchronizers(polling_builder)

ldclient/impl/datasystem/fdv1.py

@@ -142,7 +142,16 @@ def flag_tracker(self) -> FlagTracker:
 
     @property
     def data_availability(self) -> DataAvailability:
-        return self._data_availability
+        if self._config.offline:
+            return DataAvailability.DEFAULTS
+
+        if self._update_processor is not None and self._update_processor.initialized():
+            return DataAvailability.REFRESHED
+
+        if self._store_wrapper.initialized:
+            return DataAvailability.CACHED
+
+        return DataAvailability.DEFAULTS
 
     @property
     def target_availability(self) -> DataAvailability: