Warning: This is an experimental feature. It's intended for early testing and feedback, and could change without warnings in future releases.
Push sources allow feature values to be pushed to the online store and offline store in real time. This allows fresh feature values to be made available to applications. Push sources supercede the FeatureStore.write_to_online_store.
Push sources can be used by multiple feature views. When data is pushed to a push source, Feast propagates the feature values to all the consuming feature views.
Push sources must have a batch source specified. The batch source will be used for retrieving historical features. Thus users are also responsible for pushing data to a batch data source such as a data warehouse table. When using a push source as a stream source in the definition of a feature view, a batch source doesn't need to be specified in the feature view definition explicitly.
Streaming data sources are important sources of feature values. A typical setup with streaming data looks like:
Raw events come in (stream 1)
Streaming transformations applied (e.g. generating features like last_N_purchased_categories) (stream 2)
Write stream 2 values to an offline store as a historical log for training (optional)
Write stream 2 values to an online store for low latency feature serving
Periodically materialize feature values from the offline store into the online store for decreased training-serving skew and improved model performance
Feast allows users to push features previously registered in a feature view to the online store for fresher features. It also allows users to push batches of stream data to the offline store by specifying that the push be directed to the offline store. This will push the data to the offline store declared in the repository configuration used to initialize the feature store.
Defining a push source
Note that the push schema needs to also include the entity.
from feast import PushSource, ValueType, BigQuerySource, FeatureView, Feature, Field