Upsert Kafka Source Table

Function

Apache Kafka is a fast, scalable, and fault-tolerant distributed message publishing and subscription system. It delivers high throughput and built-in partitions and provides data replicas and fault tolerance. Apache Kafka is applicable to scenarios of handling massive messages.

As a source, the upsert-kafka connector produces a changelog stream, where each data record represents an update or delete event. More precisely, the value in a data record is interpreted as an UPDATE of the last value for the same key, if any (if a corresponding key does not exist yet, the UPDATE will be considered an INSERT). Using the table analogy, a data record in a changelog stream is interpreted as an UPSERT, also known as INSERT/UPDATE, because any existing row with the same key is overwritten. Also, null values are interpreted in a special way: A record with a null value represents a DELETE.

Prerequisites

• An enhanced datasource connection has been created for DLI to connect to Kafka clusters, so that jobs can run on the dedicated queue of DLI and you can set the security group rules as required.
  • For details about how to create an enhanced datasource connection, see Enhanced Datasource Connections in the Data Lake Insight User Guide.
  • For details about how to configure security group rules, see Security Group in the Virtual Private Cloud User Guide.
• In Flink cross-source development scenarios, there is a risk of password leakage if datasource authentication information is directly configured. You are advised to use the datasource authentication provided by DLI.

  For details about datasource authentication, see Introduction to Datasource Authentication.

Precautions

• When creating a Flink OpenSource SQL job, you need to set Flink Version to 1.12 on the Running Parameters tab of the job editing page, select Save Job Log, and set the OBS bucket for saving job logs.
• The Upsert Kafka always works in the upsert fashion and requires to define the primary key in the DDL. With the assumption that records with the same key should be ordered in the same partition, the primary key semantic on the changelog source means the materialized changelog is unique on the primary keys. The primary key definition will also control which fields should end up in Kafka's key.
• Because the connector is working in upsert mode, the last record on the same key will take effect when reading back as a source.
• For details about how to use data types, see section Format.

Syntax

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create table kafkaSource(
  attr_name attr_type 
  (',' attr_name attr_type)* 
  (','PRIMARY KEY (attr_name, ...) NOT ENFORCED)
)
with (
  'connector' = 'upsert-kafka',
  'topic' = '',
  'properties.bootstrap.servers' = '',
  'key.format' = '',
  'value.format' = ''
);

Parameters

Example

In this example, data is read from the Kafka data source and written to the Print result table. The procedure is as follows:

1. Create an enhanced datasource connection in the VPC and subnet where Kafka locates, and bind the connection to the required Flink elastic resource pool. For details, see Enhanced Datasource Connections.
2. Set Kafka security groups and add inbound rules to allow access from the Flink queue. Test the connectivity using the Kafka address by referring to Testing Address Connectivity. If the connection is successful, the datasource is bound to the queue. Otherwise, the binding fails.
3. Create a Flink OpenSource SQL job. Enter the following job script and submit the job.
   When you create a job, set Flink Version to 1.12 on the Running Parameters tab. Select Save Job Log, and specify the OBS bucket for saving job logs. Change the values of the parameters in bold as needed in the following script.

   CREATE TABLE upsertKafkaSource (
     order_id string,
     order_channel string,
     order_time string,
     pay_amount double,
     real_pay double,
     pay_time string,
     user_id string,
     user_name string,  
     area_id string,
     PRIMARY KEY (order_id) NOT ENFORCED
   ) WITH (
     'connector' = 'upsert-kafka',
     'topic' = 'KafkaTopic',
     'properties.bootstrap.servers' =  'KafkaAddress1:KafkaPort,KafkAddress2:KafkaPort',
     'key.format' = 'csv',
     'value.format' = 'json'
   );
   
   CREATE TABLE printSink (
     order_id string,
     order_channel string,
     order_time string,
     pay_amount double,
     real_pay double,
     pay_time string,
     user_id string,
     user_name string,  
     area_id string,
     PRIMARY KEY (order_id) NOT ENFORCED
   ) WITH (
     'connector' = 'print'
   );
   
   INSERT INTO printSink
   SELECT * FROM upsertKafkaSource;

4. Insert the following data to the specified topics in Kafka. (Note: Specify the key when inserting data to Kafka.)

   {"order_id":"202103251202020001", "order_channel":"miniAppShop", "order_time":"2021-03-25 12:02:02", "pay_amount":"60.00", "real_pay":"60.00", "pay_time":"2021-03-25 12:03:00", "user_id":"0002", "user_name":"Bob", "area_id":"330110"}
   
   {"order_id":"202103251505050001", "order_channel":"qqShop", "order_time":"2021-03-25 15:05:05", "pay_amount":"500.00", "real_pay":"400.00", "pay_time":"2021-03-25 15:10:00", "user_id":"0003", "user_name":"Cindy", "area_id":"330108"}
   
   
   {"order_id":"202103251202020001", "order_channel":"miniAppShop", "order_time":"2021-03-25 12:02:02", "pay_amount":"60.00", "real_pay":"60.00", "pay_time":"2021-03-25 12:03:00", "user_id":"0002", "user_name":"Bob", "area_id":"330110"}

5. Perform the following operations to view the output:
   1. Log in to the DLI console. In the navigation pane, choose Job Management > Flink Jobs.
   2. Click the name of the corresponding Flink job, choose Run Log, click OBS Bucket, and locate the folder of the log you want to view according to the date.
   3. Go to the folder of the date, find the folder whose name contains taskmanager, download the taskmanager.out file, and view result logs.

   The data result is as follows:

   +I(202103251202020001,miniAppShop,2021-03-2512:02:02,60.0,60.0,2021-03-2512:03:00,0002,Bob,330110)
   +I(202103251505050001,qqShop,2021-03-2515:05:05,500.0,400.0,2021-03-2515:10:00,0003,Cindy,330108)
   -U(202103251202020001,miniAppShop,2021-03-2512:02:02,60.0,60.0,2021-03-2512:03:00,0002,Bob,330110)
   +U(202103251202020001,miniAppShop,2021-03-2512:02:02,60.0,60.0,2021-03-2512:03:00,0002,Bob,330110)

FAQ

None