The distributed computing structure of Strom is called topology. It consists of stream, spout and bolt.
1.stream: A stream is a sequence of tuples (message tuples). A tuple is a list of one or more key-value pairs. It is a format for transferring data between spout and bolt, and between bolt and bolt. The format in tuple is defined in advance according to requirements and is a collection of fields.
2. spout: As the role of the data collector, connect the data source, and convert the data into a tuple and send it out as a data stream.
3. Bolt: Bolt can be understood as an operation or function in a computing program, taking one or more data streams as input, and after performing operations on the data, selectively outputting one or more data streams. Bolts can subscribe to multiple data streams emitted by spouts or other bolts, so that complex data stream transformation networks can be built.
The functions of bolt are: filtering tuples, joining (join) and aggregation operations (aggregation), computing, database read and write.