App Configuration server SDK for Python

App Configuration service provides SDK to integrate with your Python application.

Integrating server SDK for Python

App Configuration service provides SDK to integrate with your Python application. You can evaluate the values of your feature flag or property by integrating the App Configuration SDK.

Use either one of the following methods to install the SDK:

Using pip

pip install --upgrade ibm-appconfiguration-python-sdk

Using easy_install

easy_install --upgrade ibm-appconfiguration-python-sdk

In your Python application code, include the SDK module with:

from ibm_appconfiguration import AppConfiguration, Feature, Property, ConfigurationType

Initialize the sdk to connect with your App Configuration service instance.
```
appconfig_client = AppConfiguration.get_instance()
appconfig_client.init(region=AppConfiguration.REGION_US_SOUTH, guid='GUID', apikey='APIKEY')
appconfig_client.set_context(collection_id='collection_id', environment_id='environment_id')
```
Where:
- region: Region name where the service instance is created. Use AppConfiguration.REGION_US_SOUTH for Dallas, AppConfiguration.REGION_US_EAST for Washington DC, AppConfiguration.REGION_EU_GB for London, AppConfiguration.REGION_EU_DE for Frankfurt and AppConfiguration.REGION_AU_SYD for Sydney.
- guid: GUID of the App Configuration service. Obtain it from the service credentials section of the App Configuration service dashboard.
- apikey: ApiKey of the App Configuration service. Obtain it from the service credentials section of the App Configuration service dashboard.
- collection_id: ID of the collection created in App Configuration service instance.
- environment_id: ID of the environment created in App Configuration service instance.
The init() and set_context() are the initialisation methods and should be invoked only once by using appconfig_client. The appconfig_client, when initialized, can be obtained across modules by using AppConfiguration.get_instance(). For more information, see Fetching the appconfig_client across other modules.

Using private endpoints

Set the SDK to connect to App Configuration service by using a private endpoint that is accessible only through the IBM Cloud private network.

appconfig_client.use_private_endpoint(True);

This must be done before calling the init function on the SDK.

Option to use a persistent cache for configuration

For your application and SDK to continue operations even during the unlikely scenario of an App Configuration service downtime, across your application restarts, you can configure the SDK to work by using a persistent cache. The SDK uses the persistent cache to store the App Configuration data that is available across your application restarts.

# 1. default (without persistent cache)
appconfig_client.set_context(collection_id='airlines-webapp', environment_id='dev')

# 2. optional (with persistent cache)
appconfig_client.set_context(collection_id='airlines-webapp', environment_id='dev', options={
   'persistent_cache_dir': '/var/lib/docker/volumes/'
})

Where:

persistent_cache_dir: Absolute path to a directory that has read and write permission for the user. The SDK creates a file - appconfiguration.json in the specified directory, and it is used as the persistent cache to store the App Configuration service information.

When persistent cache is enabled, the SDK keeps the last known good configuration at the persistent cache. If the App Configuration server is unreachable, the latest configurations at the persistent cache are loaded to the application to continue working.

Ensure that the cache file created in the given directory is not lost or deleted in any case. For example, consider the case when a kubernetes pod is restarted and the cache file (appconfiguration.json) was stored in ephemeral volume of the pod. As pod gets restarted, kubernetes destroys the ephermal volume in the pod, as a result the cache file gets deleted. So, make sure that the cache file created by the SDK is always stored in persistent volume by providing the correct absolute path of the persistent directory.

Offline options

The SDK is also designed to serve configurations, and perform feature flag and property evaluations without being connected to App Configuration service.

appconfig_client.set_context(collection_id='collection_id', environment_id='environment_id', options={
  'bootstrap_file': 'saflights/flights.json',
  'live_config_update_enabled': False
})

Where:

bootstrap_file: Absolute path of the JSON file, which contains configuration details. Make sure to provide a proper JSON file. You can generate this file by using ibmcloud ac export command of the IBM Cloud App Configuration CLI.
live_config_update_enabled: Live configuration update from the server. Set this value to False if the new configuration values must not be fetched from the server. By default, this value is set to True.

Examples for using feature and property-related APIs

Refer to the listed examples for using the feature and property-related APIs.

Get single feature

feature = appconfig_client.get_feature('online-check-in')  # feature can be None incase of an invalid feature id

if feature is not None:
   print(f'Feature Name : {0}'.format(feature.get_feature_name()))
   print(f'Feature Id : {0}'.format(feature.get_feature_id()))
   print(f'Feature Data Type : {0}'.format(feature.get_feature_data_type()))
   if feature.is_enabled():
      # feature flag is enabled
   else:
      # feature flag is disabled

Get all features

features_dictionary = appconfig_client.get_features()

Feature evaluation

You can use the feature.get_current_value(entity_id, entity_attributes) method to evaluate the value of the feature flag. This method returns one of the Enabled or Disabled or Overridden value based on the evaluation. The data type of returned value matches that of feature flag.

entity_id = "john_doe"
entity_attributes = {
   'city': 'Bangalore',
   'country': 'India'
}
feature_value = feature.get_current_value(entity_id=entity_id, entity_attributes=entity_attributes)

entity_id: Id of the entity. This is a string identifier related to the entity against which the feature is evaluated. For example, an entity might be an instance of an app that runs on a mobile device, a microservice that runs on the cloud, or a component of infrastructure that runs that microservice. For any entity to interact with App Configuration, it must provide a unique entity ID.
entity_attributes: A JSON object consisting of the attribute name and their values that define the specified entity. This is an optional parameter if the feature flag is not configured with any targeting definition. If the targeting is configured, then entity_attributes should be provided for the rule evaluation. An attribute is a parameter that is used to define a segment. The SDK uses the attribute values to determine whether the specified entity satisfies the targeting rules, and returns the appropriate feature flag value.

Get single Property

property = appconfig_client.get_property('check-in-charges')  # property can be None incase of an invalid property id
if property is not None:
   print(f'Property Name : {0}'.format(property.get_property_name()))
   print(f'Property Id : {0}'.format(property.get_property_id()))
   print(f'Property Data Type : {0}'.format(property.get_property_data_type()))

Get all Properties

properties_dictionary = appconfig_client.get_properties()

Property evaluation

You can use the property.get_current_value(entity_id=entity_id, entity_attributes=entity_attributes) method to evaluate the value of the property. This method returns the default property value or its overridden value based on the evaluation. The data type of returned value matches that of property.

entity_id = "john_doe"
entity_attributes = {
   'city': 'Bangalore',
   'country': 'India'
}
property_value = property.get_current_value(entity_id=entity_id, entity_attributes=entity_attributes)

entity_id: Id of the entity. This is a string identifier related to the entity against which the property is evaluated. For example, an entity might be an instance of an app that runs on a mobile device, a microservice that runs on the cloud, or a component of infrastructure that runs that microservice. For any entity to interact with App Configuration, it must provide a unique entity ID.
entity_attributes: A JSON object consisting of the attribute name and their values that define the specified entity. This is an optional parameter if the property is not configured with any targeting definition. If the targeting is configured, then entity_attributes should be provided for the rule evaluation. An attribute is a parameter that is used to define a segment. The SDK uses the attribute values to determine whether the specified entity satisfies the targeting rules, and returns the appropriate property value.

Fetching the appconfig_client across other modules

When the SDK is initialized, the appconfig_client can be obtained across other modules as shown:

# **other modules**

from ibm_appconfiguration import AppConfiguration

appconfig_client = AppConfiguration.get_instance()
feature = appconfig_client.get_feature('online-check-in')
enabled = feature.is_enabled()
feature_value = feature.get_current_value(entity_id, entity_attributes)

Supported data types

You can configure feature flags and properties with App Configuration service, supporting the following data types: Boolean, Numeric, and String. The String data type can be of the format of a TEXT string, JSON, or YAML. The SDK processes each format as shown in the table.

Table 1. Example outputs
Feature or Property value	Data type	Data format	Type of data returned by `GetCurrentValue()`	Example output
`true`	BOOLEAN	Not applicable	`bool`	`true`
`25`	NUMERIC	Not applicable	`int`	`25`
"a string text"	STRING	TEXT	`string`	`a string text`
`{"firefox": {` `"name": "Firefox",` `"pref_url": "about:config"` }}	STRING	JSON	`Dictionary or List of Dictionary`	`{'firefox': {'name': 'Firefox', 'pref_url': 'about:config'}}`
`men:` `- John Smith` `- Bill Jones` `women:` `- Mary Smith` `- Susan Williams`	STRING	YAML	`Dictionary`	`{'men': ['John Smith', 'Bill Jones'], 'women': ['Mary Smith', 'Susan Williams']}`

Feature flag

feature = appconfig_client.get_feature('json-feature')
feature.get_feature_data_type() // STRING
feature.get_feature_data_format() // JSON
feature.get_current_value(entityId, entityAttributes) // returns single dictionary object or list of dictionary object

// Example Below
// input json :- [{"role": "developer", "description": "do coding"},{"role": "tester", "description": "do testing"}]
// expected output :- "do coding"

tar_val = feature.get_current_value(entityId, entityAttributes)
expected_output = tar_val[0]['description']

// input json :- {"role": "tester", "description": "do testing"}
// expected output :- "tester"

tar_val = feature.get_current_value(entityId, entityAttributes)
expected_output = tar_val['role']

feature = appconfig_client.getFeature('yaml-feature')
feature.get_feature_data_type() // STRING
feature.get_feature_data_format() // YAML
feature.get_current_value(entityId, entityAttributes) // returns dictionary object

// Example Below
// input yaml string :- "---\nrole: tester\ndescription: do_testing"
// expected output :- "do_testing"

tar_val = feature.get_current_value(entityId, entityAttributes)
expected_output = tar_val['description']

Property

property = appconfig_client.get_property('json-property')
property.get_property_data_type() // STRING
property.get_property_data_format() // JSON
property.get_current_value(entityId, entityAttributes) // returns single dictionary object or list of dictionary object

// Example Below
// input json :- [{"role": "developer", "description": "do coding"},{"role": "tester", "description": "do testing"}]
// expected output :- "do coding"

tar_val = property.get_current_value(entityId, entityAttributes)
expected_output = tar_val[0]['description']

// input json :- {"role": "tester", "description": "do testing"}
// expected output :- "tester"

tar_val = property.get_current_value(entityId, entityAttributes)
expected_output = tar_val['role']

property = appconfig_client.get_property('yaml-property')
property.get_property_data_type() // STRING
property.get_property_data_format() // YAML
property.get_current_value(entityId, entityAttributes) // returns dictionary object

// Example Below
// input yaml string :- "---\nrole: tester\ndescription: do_testing"
// expected output :- "do_testing"

tar_val = property.get_current_value(entityId, entityAttributes)
expected_output = tar_val['description']

Set listener for the feature and property data changes

The SDK provides mechanism to notify you in real time when feature flags' or properties' configuration changes. You can subscribe to configuration changes by using the same appconfig_client.

def configuration_update(self):
   print('Received updates on configurations')
   # **add your code**
   # To find the effect of any configuration changes, you can call the feature or property related methods

   # feature = appconfig_client.getFeature('online-check-in')
   # new_value = feature.get_current_value(entity_id, entity_attributes)

appconfig_client.register_configuration_update_listener(configuration_update)

Fetch latest data

appconfig_client.fetch_configurations()