Internal Training

🧠 Free Recall ❓ Quiz 🔍 Cues 🔮 Simulation 🥷 ShadowBox 📐 Encode Cards

Create an Event Streaming App with ksqlDB

An event is a piece of data that records the fact that “something happened” in the world
An event stream records the history of what has happened in the world as a sequence of events

Streams
Record History
A stream is a history of events
if you observe the changes in a table, you can record those changes to construct a stream

Tables
Represents State
A table is an evolving set of facts
As events add to the stream, the table updates its state
Tables can aggregate the whole stream, or just a specific window of time
If you are given a stream, you can construct a table of up-to-date values

You can create a stream using this syntax
Create Stream $stream_name ($stream_key_name $TYPE $Property(KEY))
CREATE STREAM
Name the stream something
Then in parenthesis detail what columns will the stream have. 
column name, the datatype, any misc properties

You can create a stream using a topic using the WITH keyword
WITH (KAFKA_TOPIC='$kafkatopic', VALUE_FORMAT=''DELIMITED', PARTITIONS=$partitionValue)
WITH 
What topic are you creating it with
What is the value format
How many partitions

You can insert into a stream using Insert Into
INSERT INTO $stream_name (columns) VALUES ('val1')

You can read from a stream using 
SELECT * FROM $stream EMIT CHANGES

The streams you create in ksqlDB are stored into Kafka topics. A Kafka topic is collection of related events. Kafka topics often become so large that they cannot fit on a single machine, so most of the time, a topic is broken down into smaller event streams called partitions. Dividing a topic into partitions also helps with performance because multiple partitions can be read at the same time in parallel.

July 27, 2021
Worked for 20 minutes. Last thing I did try to create a songs table to join it to a streams stream to get the artists with current streams.

Unstarred

Dunk (exclude from study)

Internal Training

Review Questions

Todos

Sensemaker