sql-cache-invalidation-debezium: A Java repository from Redis Developer

Caching Update with Debezium

This demonstration shows how you can use Debezium to create, update, and delete data cached in Redis.

+------------+      +-----------+       +---------+
|            |      |           |       |         |
| PostgreSQL | ---> | Debdezium |  ---> |  Redis  |
|            |      |           |       |         |
+------------+      +-----------+       +---------+

Prerequisites

Docker
- To run Postgresl & Redis
Java Developer Kit (8 or later)
Apache Maven

Running the demonstration

Get the source code from the repository

> git clone https://github.com/redis-developer/sql-cache-invalidation-debezium.git

> cd sql-cache-invalidation-debezium

Start Redis

The Java Spring application use Jedis to connect to Redis. The connection string is located in the application.properties file.

Open a new terminal and run the command:
```
> docker run -it --rm --name redis -p 6379:6379 redis
```
Build and Run PostgreSQL database

In the sql-cache-invalidation-debezium run the following commands:
```
> cd posgresql

> docker build -t postgresql-cdc .

>  docker run -it --rm --name postgresql-cdc -p 5432:5432 -e POSTGRES_PASSWORD=password postgresql-cdc
```
The PostreSQL instance is started with the configuration options needed by the Debezium Postgres Connector.

Connect to PostgreSQL & create tables

Use the Docker container to connect to PostgreSQL.

> docker exec -it postgresql-cdc bash

Connect to PostgreSQL

bash-5.0# psql -U postgres

Create table and insert rows

CREATE TABLE customers (
    customer_id serial PRIMARY KEY,
    username VARCHAR ( 50 ) UNIQUE NOT NULL,
    first_name VARCHAR ( 50 )  NOT NULL,
    last_name VARCHAR ( 50 )  NOT NULL,
    email VARCHAR ( 255 ) UNIQUE NOT NULL
);


CREATE TABLE support_level (
    level VARCHAR (30)  UNIQUE NOT NULL
);

CREATE TABLE orders (
    cust_id INT NOT NULL,
    order_type VARCHAR (10) NOT NULL,
    order_date DATE DEFAULT CURRENT_DATE,
    comments TEXT,
    PRIMARY KEY (cust_id, order_type)
);

You can check that tables are created using the command:

\dt

Insert rows into tables

INSERT INTO customers
(username, first_name, last_name, email)
VALUES
('jdoe1', 'John', 'Doe', 'jdoe1@demo.com');

Build and run the Java application

The Java application is a SpringBoot application that exposes a REST endpoint to start and stop the Debezium service. This service captures tthe connector continuously captures row-level changes that insert, update, and delete database content and that were committed to a PostgreSQL database

Open a new terminal in the sql-cache-invalidation-debezium directory and run the following commands:
```
> cd debezium-redis-demo

> mvn clean spring-boot:run
```
Start the Debezium server

Open your browser and go to:

http://localhost:8082/start

Insert new rows into tables

INSERT INTO customers
(username, first_name, last_name, email)
VALUES
('jdoe2', 'John', 'Doe', 'jdoe2@demo.com');

INSERT INTO orders
(cust_id, order_type, comments)
VALUES(1, 'ONLINE', 'comment for first order' );

INSERT INTO support_level
(level)
VALUES
('GOLD');

This last row is not synchronized to Redis since the support_level table is not in the table.include.list. (application.properties)

Note: When you restart the Debezium service, you need to send a transaction to start the replication, so be sure you reset the service using http://localhost:8082/reset if you have anty issue.