Flink CDC sources #

-- creates a mysql cdc table source
CREATE TABLE mysql_binlog (
 id INT NOT NULL,
 name STRING,
 description STRING,
 weight DECIMAL(10,3),
 PRIMARY KEY(id) NOT ENFORCED
) 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;

import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.cdc.debezium.JsonDebeziumDeserializationSchema;
import org.apache.flink.cdc.connectors.mysql.source.MySqlSource;

public class MySqlBinlogSourceExample {
  public static void main(String[] args) throws Exception {
    MySqlSource<String> mySqlSource = MySqlSource.<String>builder()
            .hostname("yourHostname")
            .port(yourPort)
            .databaseList("yourDatabaseName") // set captured database
            .tableList("yourDatabaseName.yourTableName") // set captured table
            .username("yourUsername")
            .password("yourPassword")
            .deserializer(new JsonDebeziumDeserializationSchema()) // converts SourceRecord to JSON String
            .build();
    
    StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
    
    // enable checkpoint
    env.enableCheckpointing(3000);
    
    env
      .fromSource(mySqlSource, WatermarkStrategy.noWatermarks(), "MySQL Source")
      // set 4 parallel source tasks
      .setParallelism(4)
      .print().setParallelism(1); // use parallelism 1 for sink to keep message ordering
    
    env.execute("Print MySQL Snapshot + Binlog");
  }
}

{
  "before": {
    "id": 111,
    "name": "scooter",
    "description": "Big 2-wheel scooter",
    "weight": 5.18
  },
  "after": {
    "id": 111,
    "name": "scooter",
    "description": "Big 2-wheel scooter",
    "weight": 5.15
  },
  "source": {...},
  "op": "u",  // the operation type, "u" means this this is an update event 
  "ts_ms": 1589362330904,  // the time at which the connector processed the event
  "transaction": null
}

{
  "schema": {
    "type": "struct",
    "fields": [
      {
        "type": "struct",
        "fields": [
          {
            "type": "int32",
            "optional": false,
            "field": "id"
          },
          {
            "type": "string",
            "optional": false,
            "default": "flink",
            "field": "name"
          },
          {
            "type": "string",
            "optional": true,
            "field": "description"
          },
          {
            "type": "double",
            "optional": true,
            "field": "weight"
          }
        ],
        "optional": true,
        "name": "mysql_binlog_source.inventory_1pzxhca.products.Value",
        "field": "before"
      },
      {
        "type": "struct",
        "fields": [
          {
            "type": "int32",
            "optional": false,
            "field": "id"
          },
          {
            "type": "string",
            "optional": false,
            "default": "flink",
            "field": "name"
          },
          {
            "type": "string",
            "optional": true,
            "field": "description"
          },
          {
            "type": "double",
            "optional": true,
            "field": "weight"
          }
        ],
        "optional": true,
        "name": "mysql_binlog_source.inventory_1pzxhca.products.Value",
        "field": "after"
      },
      {
        "type": "struct",
        "fields": {...}, 
        "optional": false,
        "name": "io.debezium.connector.mysql.Source",
        "field": "source"
      },
      {
        "type": "string",
        "optional": false,
        "field": "op"
      },
      {
        "type": "int64",
        "optional": true,
        "field": "ts_ms"
      }
    ],
    "optional": false,
    "name": "mysql_binlog_source.inventory_1pzxhca.products.Envelope"
  },
  "payload": {
    "before": {
      "id": 111,
      "name": "scooter",
      "description": "Big 2-wheel scooter",
      "weight": 5.18
    },
    "after": {
      "id": 111,
      "name": "scooter",
      "description": "Big 2-wheel scooter",
      "weight": 5.15
    },
    "source": {...},
    "op": "u",  // the operation type, "u" means this this is an update event
    "ts_ms": 1589362330904,  // the time at which the connector processed the event
    "transaction": null
  }
}

 Map<String, Object> customConverterConfigs = new HashMap<>();
 customConverterConfigs.put(JsonConverterConfig.DECIMAL_FORMAT_CONFIG, "numeric");
 JsonDebeziumDeserializationSchema schema = 
      new JsonDebeziumDeserializationSchema(true, customConverterConfigs);