ajsharp/feature_gate

FeatureGate

Featuregate is a simple feature flag API similar to Flipper.

Configuration

PosthogAdapter

export POSTHOG_API_KEY="someapikey"
export POSTHOG_PROJECT_ID="someprojectid"

Usage

from feature_gate.client import Client
from feature_gate.adapters import PosthogAdapter
from feature_gate.feature import Feature

adapter = PosthogAdapter() # Or MemoryAdapter for testing
client = Client(adapter)
feature = Feature("Test flag", "test_flag", "This is a test flag")

client.features()
# => []

client.add(feature)
# => True

client.features()
# => ["test_flag"]

client.is_enabled("test_flag")
# => False

client.enable("test_flag")
# => True

client.is_enabled("test_flag")
# => True

client.disable("test_flag")
# => True

client.is_enabled("test_flag")
# => False

client.remove("test_flag")
# => True

client.features()
# => []

Errors

FeatureNotFound

If you try to run something that presumes the existence of a feature and it can't find it it'll throw a FeatureNotFound.

from feature_gate.client import FeatureNotFound

try:
  client.remove("some_feature_that_definitely_does_not_exist")
except FeatureNotFound as err:
  # Do what we want to do when the feature doesn't exist

PostApiClientError

For the PosthogAdapter in particular it will raise error if it was unable to reach the Posthog API. These get bubbled up as PosthogAPIClientError.

from feature_gate.clients.posthog_api_client import PosthogAPIClientError

try:
  client.features() #disable network connection
except PosthogAPIClientError as err:
  # Handle the error -- define default behavior in outage

Testing

The Memory Adapter can be used for writing tests. This creates an ephemeral memory only implementation of the feature_gate client API. This is non-suitable for production only for tests.

from feature_gate.client import Client
from feature_gate.adapters.memory import MemoryAdapter

client = Client(MemoryAdapter())

Developing this library

Hot-reload the REPL

Hot-reload the client in the repl for development:

$ repl
>>> exec(open('reload.py').read())