CDC Connectors for Apache Flink<sup>®</sup> is a set of source connectors for Apache Flink<sup>®</sup>, ingesting changes from different databases using change data capture (CDC).
CDC Connectors for Apache Flink<sup>®</sup> integrates Debezium as the engine to capture data changes. So it can fully leverage the ability of Debezium. See more about what is [Debezium](https://github.com/debezium/debezium).
This README is meant as a brief walkthrough on the core features of CDC Connectors for Apache Flink<sup>®</sup>. For a fully detailed documentation, please see [Documentation](https://ververica.github.io/flink-cdc-connectors/master/).
2. Download the connector SQL jars from the [Download](https://github.com/ververica/flink-cdc-connectors/releases) page (or [build yourself](#building-from-source)).
3. Put the downloaded jars under `FLINK_HOME/lib/`.
4. Restart the Flink cluster.
The example shows how to create a MySQL CDC source in [Flink SQL Client](https://ci.apache.org/projects/flink/flink-docs-release-1.13/dev/table/sqlClient.html) and execute queries on it.
```sql
-- creates a mysql cdc table source
CREATE TABLE mysql_binlog (
id INT NOT NULL,
name STRING,
description STRING,
weight DECIMAL(10,3)
) WITH (
'connector' = 'mysql-cdc',
'hostname' = 'localhost',
'port' = '3306',
'username' = 'flinkuser',
'password' = 'flinkpw',
'database-name' = 'inventory',
'table-name' = 'products'
);
-- read snapshot and binlog data from mysql, and do some transformation, and show on the client
SELECT id, UPPER(name), description, weight FROM mysql_binlog;
```
## Usage for DataStream API
Include following Maven dependency (available through Maven Central):
```
<dependency>
<groupId>com.ververica</groupId>
<!-- add the dependency matching your database -->
CDC Connectors for Apache Flink<sup>®</sup> welcomes anyone that wants to help out in any way, whether that includes reporting problems, helping with documentation, or contributing code changes to fix bugs, add tests, or implement new features. You can report problems to request features in the [GitHub Issues](https://github.com/ververica/flink-cdc-connectors/issues).
6. Open a PR to https://github.com/ververica/flink-cdc-connectors
### Code Style
#### Code Formatting
You need to install the google-java-format plugin. Spotless together with google-java-format is used to format the codes.
It is recommended to automatically format your code by applying the following settings:
1. Go to "Settings" → "Other Settings" → "google-java-format Settings".
2. Tick the checkbox to enable the plugin.
3. Change the code style to "Android Open Source Project (AOSP) style".
4. Go to "Settings" → "Tools" → "Actions on Save".
5. Under "Formatting Actions", select "Optimize imports" and "Reformat file".
6. From the "All file types list" next to "Reformat code", select "Java".
For earlier IntelliJ IDEA versions, the step 4 to 7 will be changed as follows.
- 4.Go to "Settings" → "Other Settings" → "Save Actions".
- 5.Under "General", enable your preferred settings for when to format the code, e.g. "Activate save actions on save".
- 6.Under "Formatting Actions", select "Optimize imports" and "Reformat file".
- 7.Under "File Path Inclusions", add an entry for `.*\.java` to avoid formatting other file types.
Then the whole project could be formatted by command `mvn spotless:apply`.
#### Checkstyle
Checkstyle is used to enforce static coding guidelines.
1. Go to "Settings" → "Tools" → "Checkstyle".
2. Set "Scan Scope" to "Only Java sources (including tests)".
3. For "Checkstyle Version" select "8.14".
4. Under "Configuration File" click the "+" icon to add a new configuration.
5. Set "Description" to "Flink cdc".
6. Select "Use a local Checkstyle file" and link it to the file `tools/maven/checkstyle.xml` which is located within your cloned repository.
7. Select "Store relative to project location" and click "Next".
8. Configure the property `checkstyle.suppressions.file` with the value `suppressions.xml` and click "Next".
9. Click "Finish".
10. Select "Flink cdc" as the only active configuration file and click "Apply".
You can now import the Checkstyle configuration for the Java code formatter.
1. Go to "Settings" → "Editor" → "Code Style" → "Java".
2. Click the gear icon next to "Scheme" and select "Import Scheme" → "Checkstyle Configuration".
3. Navigate to and select `tools/maven/checkstyle.xml` located within your cloned repository.
Then you could click "View" → "Tool Windows" → "Checkstyle" and find the "Check Module" button in the opened tool window to validate checkstyle. Or you can use the command `mvn clean compile checkstyle:checkstyle` to validate.
### Documentation Contribute
Flink cdc documentations locates at `docs/content`.
The contribution step is the same as the code contribution. We use markdown as the source code of the document.
