Common Concepts

Topology

A computing stream chart, in which each node contains processing logic and the lines between nodes specify data flow between nodes.

Spout

A component that generates source data streams in a Topology. A Spout reads data from an external data source and converts the data into source data inside a Topology.

Bolt

A component that receives data from a Topology and then processes data. A Bolt can perform operations, such as filtering, executing functions, combination, and writing data into a database.

Tuple

Basic unit for transferring messages once.

Stream

A set of (infinite) elements, each of which belongs to a same schema. Each element is related to the logic time, that is, a Stream has the Tuple and Time attributes. Any elements can be expressed in the format of Element<Tuple,Time>, in which Tuple includes the data structure and content, and Time is the logic time of data.

keytab file

A key file used for storing user information. Applications use the key file for API authentication on service.