feat(flagd-rpc): add caching with tests

Signed-off-by: Simon Schrottner <simon.schrottner@dynatrace.com>

providers/openfeature-provider-flagd/pyproject.toml

@@ -24,6 +24,7 @@ dependencies = [
   "panzi-json-logic>=1.0.1",
   "semver>=3,<4",
   "pyyaml>=6.0.1",
+  "cachebox"
 ]
 requires-python = ">=3.8"
 
@@ -46,7 +47,7 @@ pre-install-commands = [
 ]
 
 [tool.hatch.envs.hatch-test.scripts]
-run = "pytest {args:tests}"
+run = "pytest -m 'not customCert and not unixsocket and not (sync and not events)' {args:tests}"
 run-cov = "coverage run -m pytest {args:tests}"
 cov-combine = "coverage combine"
 cov-report = [
@@ -59,6 +60,7 @@ cov = [
   "cov-report",
 ]
 
+
 [tool.hatch.envs.mypy]
 dependencies = [
   "mypy[faster-cache]>=1.13.0",

providers/openfeature-provider-flagd/pytest.ini

@@ -0,0 +1,10 @@
+[pytest]
+markers =
+    rpc: tests for rpc mode.
+    in-process: tests for rpc mode.
+    customCert: Supports custom certs.
+    unixsocket: Supports unixsockets.
+    events: Supports events.
+    sync: Supports sync.
+    caching: Supports caching.
+    offline: Supports offline.

providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/config.py

@@ -8,6 +8,13 @@ class ResolverType(Enum):
     IN_PROCESS = "in-process"
 
 
+class CacheType(Enum):
+    LRU = "lru"
+    DISABLED = "disabled"
+
+
+DEFAULT_CACHE = CacheType.LRU
+DEFAULT_CACHE_SIZE = 1000
 DEFAULT_DEADLINE = 500
 DEFAULT_HOST = "localhost"
 DEFAULT_KEEP_ALIVE = 0
@@ -19,12 +26,14 @@ class ResolverType(Enum):
 DEFAULT_STREAM_DEADLINE = 600000
 DEFAULT_TLS = False
 
+ENV_VAR_CACHE_SIZE = "FLAGD_MAX_CACHE_SIZE"
+ENV_VAR_CACHE_TYPE = "FLAGD_CACHE"
 ENV_VAR_DEADLINE_MS = "FLAGD_DEADLINE_MS"
 ENV_VAR_HOST = "FLAGD_HOST"
 ENV_VAR_KEEP_ALIVE_TIME_MS = "FLAGD_KEEP_ALIVE_TIME_MS"
 ENV_VAR_OFFLINE_FLAG_SOURCE_PATH = "FLAGD_OFFLINE_FLAG_SOURCE_PATH"
 ENV_VAR_PORT = "FLAGD_PORT"
-ENV_VAR_RESOLVER_TYPE = "FLAGD_RESOLVER_TYPE"
+ENV_VAR_RESOLVER_TYPE = "FLAGD_RESOLVER"
 ENV_VAR_RETRY_BACKOFF_MS = "FLAGD_RETRY_BACKOFF_MS"
 ENV_VAR_STREAM_DEADLINE_MS = "FLAGD_STREAM_DEADLINE_MS"
 ENV_VAR_TLS = "FLAGD_TLS"
@@ -57,6 +66,8 @@ def __init__(  # noqa: PLR0913
         deadline: typing.Optional[int] = None,
         stream_deadline_ms: typing.Optional[int] = None,
         keep_alive_time: typing.Optional[int] = None,
+        cache_type: typing.Optional[CacheType] = None,
+        max_cache_size: typing.Optional[int] = None,
     ):
         self.host = env_or_default(ENV_VAR_HOST, DEFAULT_HOST) if host is None else host
 
@@ -125,3 +136,15 @@ def __init__(  # noqa: PLR0913
             if keep_alive_time is None
             else keep_alive_time
         )
+
+        self.cache_type = (
+            CacheType(env_or_default(ENV_VAR_CACHE_TYPE, DEFAULT_CACHE))
+            if cache_type is None
+            else cache_type
+        )
+
+        self.max_cache_size: int = (
+            int(env_or_default(ENV_VAR_CACHE_SIZE, DEFAULT_CACHE_SIZE, cast=int))
+            if max_cache_size is None
+            else max_cache_size
+        )

providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/provider.py

@@ -29,7 +29,7 @@
 from openfeature.provider.metadata import Metadata
 from openfeature.provider.provider import AbstractProvider
 
-from .config import Config, ResolverType
+from .config import CacheType, Config, ResolverType
 from .resolvers import AbstractResolver, GrpcResolver, InProcessResolver
 
 T = typing.TypeVar("T")
@@ -50,6 +50,8 @@ def __init__(  # noqa: PLR0913
         offline_flag_source_path: typing.Optional[str] = None,
         stream_deadline_ms: typing.Optional[int] = None,
         keep_alive_time: typing.Optional[int] = None,
+        cache_type: typing.Optional[CacheType] = None,
+        max_cache_size: typing.Optional[int] = None,
     ):
         """
         Create an instance of the FlagdProvider
@@ -83,6 +85,8 @@ def __init__(  # noqa: PLR0913
             offline_flag_source_path=offline_flag_source_path,
             stream_deadline_ms=stream_deadline_ms,
             keep_alive_time=keep_alive_time,
+            cache_type=cache_type,
+            max_cache_size=max_cache_size,
         )
 
         self.resolver = self.setup_resolver()

providers/openfeature-provider-flagd/src/openfeature/contrib/provider/flagd/resolvers/grpc.py

@@ -4,6 +4,7 @@
 import typing
 
 import grpc
+from cachebox import BaseCacheImpl, LRUCache
 from google.protobuf.json_format import MessageToDict
 from google.protobuf.struct_pb2 import Struct
 
@@ -18,13 +19,13 @@
     ProviderNotReadyError,
     TypeMismatchError,
 )
-from openfeature.flag_evaluation import FlagResolutionDetails
+from openfeature.flag_evaluation import FlagResolutionDetails, Reason
 from openfeature.schemas.protobuf.flagd.evaluation.v1 import (
     evaluation_pb2,
     evaluation_pb2_grpc,
 )
 
-from ..config import Config
+from ..config import CacheType, Config
 from ..flag_type import FlagType
 
 if typing.TYPE_CHECKING:
@@ -57,6 +58,12 @@ def __init__(
         self.deadline = config.deadline * 0.001
         self.connected = False
 
+        self._cache: typing.Optional[BaseCacheImpl] = (
+            LRUCache(maxsize=self.config.max_cache_size)
+            if self.config.cache_type == CacheType.LRU
+            else None
+        )
+
     def _create_stub(
         self,
     ) -> typing.Tuple[evaluation_pb2_grpc.ServiceStub, grpc.Channel]:
@@ -71,10 +78,20 @@ def _create_stub(
 
     def initialize(self, evaluation_context: EvaluationContext) -> None:
         self.connect()
+        self.retry_backoff_seconds = 0.1
+        self.connected = False
+
+        self._cache = (
+            LRUCache(maxsize=self.config.max_cache_size)
+            if self.config.cache_type == CacheType.LRU
+            else None
+        )
 
     def shutdown(self) -> None:
         self.active = False
         self.channel.close()
+        if self._cache:
+            self._cache.clear()
 
     def connect(self) -> None:
         self.active = True
@@ -96,7 +113,6 @@ def connect(self) -> None:
 
     def listen(self) -> None:
         retry_delay = self.retry_backoff_seconds
-
         call_args = (
             {"timeout": self.streamline_deadline_seconds}
             if self.streamline_deadline_seconds > 0
@@ -148,6 +164,10 @@ def listen(self) -> None:
     def handle_changed_flags(self, data: typing.Any) -> None:
         changed_flags = list(data["flags"].keys())
 
+        if self._cache:
+            for flag in changed_flags:
+                self._cache.pop(flag)
+
         self.emit_provider_configuration_changed(ProviderEventDetails(changed_flags))
 
     def resolve_boolean_details(
@@ -190,13 +210,18 @@ def resolve_object_details(
     ) -> FlagResolutionDetails[typing.Union[dict, list]]:
         return self._resolve(key, FlagType.OBJECT, default_value, evaluation_context)
 
-    def _resolve(  # noqa: PLR0915
+    def _resolve(  # noqa: PLR0915 C901
         self,
         flag_key: str,
         flag_type: FlagType,
         default_value: T,
         evaluation_context: typing.Optional[EvaluationContext],
     ) -> FlagResolutionDetails[T]:
+        if self._cache is not None and flag_key in self._cache:
+            cached_flag: FlagResolutionDetails[T] = self._cache[flag_key]
+            cached_flag.reason = Reason.CACHED
+            return cached_flag
+
         context = self._convert_context(evaluation_context)
         call_args = {"timeout": self.deadline}
         try:
@@ -249,12 +274,17 @@ def _resolve(  # noqa: PLR0915
             raise GeneralError(message) from e
 
         # Got a valid flag and valid type. Return it.
-        return FlagResolutionDetails(
+        result = FlagResolutionDetails(
             value=value,
             reason=response.reason,
             variant=response.variant,
         )
 
+        if response.reason == Reason.STATIC and self._cache is not None:
+            self._cache.insert(flag_key, result)
+
+        return result
+
     def _convert_context(
         self, evaluation_context: typing.Optional[EvaluationContext]
     ) -> Struct: