CDC Connector

Source

The CDC Source connector is used to capture change log of existing databases like MySQL, MongoDB, PostgreSQL into Pulsar.

The CDC Source connector is built on top of Debezium. This connector stores all data into Pulsar Cluster in a persistent, replicated and partitioned way. This CDC Source are tested by using MySQL, and you could get more information regarding how it works at this link. Regarding how Debezium works, please reference to Debezium tutorial. It is recommended that you go through this tutorial first.

Source Configuration Options

The Configuration is mostly related to Debezium task config, besides this we should provides the service URL of Pulsar cluster, and topic names that used to store offset and history.

Name	Required	Default	Description
`task.class`	`true`	`null`	A source task class that implemented in Debezium.
`database.hostname`	`true`	`null`	The address of the Database server.
`database.port`	`true`	`null`	The port number of the Database server..
`database.user`	`true`	`null`	The name of the Database user that has the required privileges.
`database.password`	`true`	`null`	The password for the Database user that has the required privileges.
`database.server.id`	`true`	`null`	The connector’s identifier that must be unique within the Database cluster and similar to Database’s server-id configuration property.
`database.server.name`	`true`	`null`	The logical name of the Database server/cluster, which forms a namespace and is used in all the names of the Kafka topics to which the connector writes, the Kafka Connect schema names, and the namespaces of the corresponding Avro schema when the Avro Connector is used.
`database.whitelist`	`false`	`null`	A list of all databases hosted by this server that this connector will monitor. This is optional, and there are other properties for listing the databases and tables to include or exclude from monitoring.
`key.converter`	`true`	`null`	The converter provided by Kafka Connect to convert record key.
`value.converter`	`true`	`null`	The converter provided by Kafka Connect to convert record value.
`database.history`	`true`	`null`	The name of the database history class name.
`database.history.pulsar.topic`	`true`	`null`	The name of the database history topic where the connector will write and recover DDL statements. This topic is for internal use only and should not be used by consumers.
`database.history.pulsar.service.url`	`true`	`null`	Pulsar cluster service url for history topic.
`pulsar.service.url`	`true`	`null`	Pulsar cluster service URL for the offset topic used in Debezium. You can use the `bin/pulsar-admin --admin-url http://pulsar:8080 sources localrun --source-config-file configs/pg-pulsar-config.yaml` command to point to the target Pulsar cluster.
`offset.storage.topic`	`true`	`null`	Record the last committed offsets that the connector successfully completed.

Configuration Example

Here is a configuration Json example:

{
    "tenant": "public",
    "namespace": "default",
    "name": "debezium-kafka-source",
    "className": "org.apache.pulsar.io.kafka.connect.KafkaConnectSource" ,
    "topicName": "kafka-connect-topic",
    "configs":
    {
        "task.class": "io.debezium.connector.mysql.MySqlConnectorTask",
        "database.hostname": "localhost",
        "database.port": "3306",
        "database.user": "debezium",
        "database.password": "dbz",
        "database.server.id": "184054",
        "database.server.name": "dbserver1",
        "database.whitelist": "inventory",
        "database.history": "org.apache.pulsar.io.debezium.PulsarDatabaseHistory",
        "database.history.pulsar.topic": "history-topic",
        "database.history.pulsar.service.url": "pulsar://127.0.0.1:6650",
        "key.converter": "org.apache.kafka.connect.json.JsonConverter",
        "value.converter": "org.apache.kafka.connect.json.JsonConverter",
        "pulsar.service.url": "pulsar://127.0.0.1:6650",
        "offset.storage.topic": "offset-topic"
    },
    "archive": "connectors/pulsar-io-kafka-connect-adaptor-2.3.0-SNAPSHOT.nar"
}

You could also find the yaml example in this file, which has similar content below:

tenant: "public"
namespace: "default"
name: "debezium-kafka-source"
topicName: "kafka-connect-topic"
archive: "connectors/pulsar-io-kafka-connect-adaptor-2.3.0-SNAPSHOT.nar"

##autoAck: true
parallelism: 1

configs:
  ## sourceTask
  task.class: "io.debezium.connector.mysql.MySqlConnectorTask"

  ## config for mysql, docker image: debezium/example-mysql:0.8
  database.hostname: "localhost"
  database.port: "3306"
  database.user: "debezium"
  database.password: "dbz"
  database.server.id: "184054"
  database.server.name: "dbserver1"
  database.whitelist: "inventory"

  database.history: "org.apache.pulsar.io.debezium.PulsarDatabaseHistory"
  database.history.pulsar.topic: "history-topic"
  database.history.pulsar.service.url: "pulsar://127.0.0.1:6650"
  ## KEY_CONVERTER_CLASS_CONFIG, VALUE_CONVERTER_CLASS_CONFIG
  key.converter: "org.apache.kafka.connect.json.JsonConverter"
  value.converter: "org.apache.kafka.connect.json.JsonConverter"
  ## PULSAR_SERVICE_URL_CONFIG
  pulsar.service.url: "pulsar://127.0.0.1:6650"
  ## OFFSET_STORAGE_TOPIC_CONFIG
  offset.storage.topic: "offset-topic"

Usage example

Here is a simple example to store MySQL change data using above example config.

Start a MySQL server with an example database, from which Debezium can capture changes.

 docker run -it --rm --name mysql -p 3306:3306 -e MYSQL_ROOT_PASSWORD=debezium -e MYSQL_USER=mysqluser -e MYSQL_PASSWORD=mysqlpw debezium/example-mysql:0.8

Start a Pulsar service locally in standalone mode.

 bin/pulsar standalone

Start pulsar debezium connector, with local run mode, and using above yaml config file. Please make sure that the nar file is available as configured in path connectors/pulsar-io-kafka-connect-adaptor-2.3.0-SNAPSHOT.nar.

 bin/pulsar-admin source localrun  --sourceConfigFile debezium-mysql-source-config.yaml

Subscribe the topic for table inventory.products.

 bin/pulsar-client consume -s "sub-products" public/default/dbserver1.inventory.products -n 0

start a MySQL cli docker connector, and use it we could change to the table products in MySQL server.

$docker run -it --rm --name mysqlterm --link mysql --rm mysql:5.7 sh -c 'exec mysql -h"$MYSQL_PORT_3306_TCP_ADDR" -P"$MYSQL_PORT_3306_TCP_PORT" -uroot -p"$MYSQL_ENV_MYSQL_ROOT_PASSWORD"'

This command will pop out MySQL cli, in this cli, we could do a change in table products, use commands below to change the name of 2 items in table products:

mysql> use inventory;
mysql> show tables;
mysql> SELECT * FROM  products ;
mysql> UPDATE products SET name='1111111111' WHERE id=101;
mysql> UPDATE products SET name='1111111111' WHERE id=107;