Canal Format

Canal Format是CDC(Changelog Data Capture)工具，能在实时系统中处理mysql binlog数据。内部默认使用JSON和Protobuf进行序列化。

应用场景：

1. 从数据库同步增量数据到其他系统
2. 审计
3. 数据库的实时物化视图
4. 与数据库历史数据temporal join

Flink RowKind

1. INSERT(+I)
2. DELETE(-D)
3. UPDATE_BEFORE(-U)
4. UPDATE_ARTER(+U)

Canal格式

{
  "data": [
    {
      "id": "111",
      "name": "scooter",
      "description": "Big 2-wheel scooter",
      "weight": "5.18"
    }
  ],
  "database": "inventory",
  "es": 1589373560000,
  "id": 9,
  "isDdl": false,
  "mysqlType": {
    "id": "INTEGER",
    "name": "VARCHAR(255)",
    "description": "VARCHAR(512)",
    "weight": "FLOAT"
  },
  "old": [
    {
      "weight": "5.15"
    }
  ],
  "pkNames": [
    "id"
  ],
  "sql": "",
  "sqlType": {
    "id": 4,
    "name": 12,
    "description": 12,
    "weight": 7
  },
  "table": "products",
  "ts": 1589373560798,
  "type": "UPDATE"
}

MySQL products 表有4列（id，name，description 和 weight）。上面的 JSON 消息是 products 表上的一个更新事件，表示 id = 111 的行数据上 weight 字段值从5.15变更成为 5.18。假设消息已经同步到了一个 Kafka 主题：products_binlog，那么就可以使用以下DDL来从这个主题消费消息并解析变更事件。

用例

CREATE TABLE topic_products (
  -- schema is totally the same to the MySQL "products" table
  id BIGINT,
  name STRING,
  description STRING,
  weight DECIMAL(10, 2)
) WITH (
 'connector' = 'kafka',
 'topic' = 'products_binlog',
 'properties.bootstrap.servers' = 'localhost:9092',
 'properties.group.id' = 'testGroup',
 'format' = 'canal-json'  -- using canal-json as the format
)

SET 'topic_products.format'='canal-json';

Format参数