Python provider
Installation
Configuration and Usage
The flagd provider can operate in two modes: RPC (evaluation takes place in flagd, via gRPC calls) or in-process (evaluation takes place in-process, with the provider getting a ruleset from a compliant sync-source).
Remote resolver (RPC)
This is the default mode of operation of the provider.
In this mode, FlagdProvider communicates with flagd via the gRPC protocol.
Flag evaluations take place remotely at the connected flagd instance.
Instantiate a new FlagdProvider instance and configure the OpenFeature SDK to use it:
from openfeature import api
from openfeature.contrib.provider.flagd import FlagdProvider
api.set_provider(FlagdProvider())
In-process resolver
This mode performs flag evaluations locally (in-process). Flag configurations for evaluation are obtained via gRPC protocol using sync protobuf schema service definition.
Consider the following example to create a FlagdProvider with in-process evaluations,
from openfeature import api
from openfeature.contrib.provider.flagd import FlagdProvider
from openfeature.contrib.provider.flagd.config import ResolverType
api.set_provider(FlagdProvider(
resolver_type=ResolverType.IN_PROCESS,
))
In the above example, in-process handlers attempt to connect to a sync service on address localhost:8013 to obtain flag definitions.
File mode
In-process resolvers can also work in an offline mode.
To enable this mode, you should provide a valid flag configuration file with the option offlineFlagSourcePath.
from openfeature import api
from openfeature.contrib.provider.flagd import FlagdProvider
from openfeature.contrib.provider.flagd.config import ResolverType
api.set_provider(FlagdProvider(
resolver_type=ResolverType.FILE,
offline_flag_source_path="my-flag.json",
))
Provider will attempt to detect file changes using polling. Polling happens at 5 second intervals and this is currently unconfigurable. This mode is useful for local development, tests and offline applications.
Configuration options
The default options can be defined in the FlagdProvider constructor.
| Option name | Environment variable name | Type & Values | Default | Compatible resolver |
|---|---|---|---|---|
| resolver_type | FLAGD_RESOLVER | enum - rpc, in-process |
rpc | |
| host | FLAGD_HOST | str | localhost | rpc & in-process |
| port | FLAGD_PORT | int | 8013 (rpc), 8015 (in-process) | rpc & in-process |
| tls | FLAGD_TLS | bool | false | rpc & in-process |
| cert_path | FLAGD_SERVER_CERT_PATH | String | null | rpc & in-process |
| deadline | FLAGD_DEADLINE_MS | int | 500 | rpc & in-process |
| stream_deadline_ms | FLAGD_STREAM_DEADLINE_MS | int | 600000 | rpc & in-process |
| keep_alive_time | FLAGD_KEEP_ALIVE_TIME_MS | int | 0 | rpc & in-process |
| selector | FLAGD_SOURCE_SELECTOR | str | null | in-process |
| cache_type | FLAGD_CACHE | enum - lru, disabled |
lru | rpc |
| max_cache_size | FLAGD_MAX_CACHE_SIZE | int | 1000 | rpc |
| retry_backoff_ms | FLAGD_RETRY_BACKOFF_MS | int | 1000 | rpc |
| offline_flag_source_path | FLAGD_OFFLINE_FLAG_SOURCE_PATH | str | null | in-process |
[!NOTE] Some configurations are only applicable for RPC resolver.
Reconnection
Reconnection is supported by the underlying gRPC connections. If the connection to flagd is lost, it will reconnect automatically. A failure to connect will result in an error event from the provider, though it will attempt to reconnect indefinitely.
Deadlines
Deadlines are used to define how long the provider waits to complete initialization or flag evaluations. They behave differently based on the resolver type.
Deadlines with Remote resolver (RPC)
If the remote evaluation call is not completed within this deadline, the gRPC call is terminated with the error DEADLINE_EXCEEDED
and the evaluation will default.
TLS
TLS is available in situations where flagd is running on another host.
You may optionally supply an X.509 certificate in PEM format. Otherwise, the default certificate store will be used.