Kafka Result Table

Updated on 2025-01-10 GMT+08:00

View PDF

Function

DLI outputs the Flink job output data to Kafka through the Kafka result table.

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.

Prerequisites

You have created a Kafka cluster.
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 set up 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 Overview 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.
For details about how to use data types, see section Format.

Syntax

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

Parameters

**Table 1** Parameter description
Parameter	Mandatory	Default Value	Data Type	Description
connector	Yes	None	string	Connector to be used. Set this parameter to kafka.
topic	Yes	None	string	Topic name of the Kafka result table.
properties.bootstrap.servers	Yes	None	string	Kafka broker address. The value is in the format of host:port,host:port,host:port. Multiple host:port pairs are separated with commas (,).
format	Yes	None	string	Format used by the Flink Kafka connector to serialize Kafka messages. Either this parameter or the value.format parameter is required. The following formats are supported: csv json avro Refer to Format for more details and format parameters.
topic-pattern	No	None	String	Regular expression for matching the Kafka topic name. Only one of topic and topic-pattern can be specified. Example: 'topic.' '(topic-c\|topic-d)' '(topic-a\|topic-b\|topic-\\d)' '(topic-a\|topic-b\|topic-[0-9]*)'
properties.*	No	None	String	This parameter can set and pass arbitrary Kafka configurations. Note: Suffix names must match the configuration key defined in Apache Kafka. For example, you can disable automatic topic creation via 'properties.allow.auto.create.topics' = 'false'. Some configurations are not supported, for example, 'key.deserializer' and 'value.deserializer'.
key.format	No	None	String	Format used to deserialize and serialize the key part of Kafka messages. Note: If a key format is defined, the key.fields parameter is required as well. Otherwise, the Kafka records will have an empty key. Possible values are: csv json avro debezium-json canal-json maxwell-json avro-confluent raw Refer to Format for more details and format parameters.
key.fields	No	[]	List<String>	Defines the columns in the table as the list of keys. This parameter must be configured in pair with key.format. This parameter is left empty by default. Therefore, no key is defined. The format is like field1;field2.
key.fields-prefix	No	None	String	Defines a custom prefix for all fields of the key format to avoid name clashes with fields of the value format.
value.format	Yes	None	String	Format used to deserialize and serialize the value part of Kafka messages. Note: Either this parameter or the format parameter is required. If two parameters are configured, a conflict occurs. Refer to Format for more details and format parameters.
value.fields-include	No	ALL	Enum Possible values: [ALL, EXCEPT_KEY]	Whether to contain the key field when parsing the message body. Possible values are: ALL (default): All defined fields are included in the value of Kafka messages. EXCEPT_KEY: All the fields except those defined by key.fields are included in the value of Kafka messages.
sink.partitioner	No	None	string	Mapping from Flink's partitions into Kafka's partitions. Valid values are as follows: fixed (default): Each Flink partition ends up in at most one Kafka partition. round-robin: A Flink partition is distributed to Kafka partitions in a round-robin manner. Custom FlinkKafkaPartitioner subclass: If fixed and round-robin do not meet your requirements, you can create subclass FlinkKafkaPartitioner to customize the partition mapping, for example, org.mycompany.MyPartitioner.
sink.semantic	No	at-least-once	String	Defines the delivery semantic for the Kafka sink. Valid values are as follows: at-least-once exactly-once none
sink.parallelism	No	None	Integer	Defines the parallelism of the Kafka sink operator. By default, the parallelism is determined by the framework using the same parallelism of the upstream chained operator.
ssl_auth_name	No	None	String	Name of datasource authentication of the Kafka_SSL type created on DLI. This configuration is used when SSL is configured for Kafka. Note: If only the SSL type is used, you need to set properties.security.protocol to SSL. If the SASL_SSL type is used, you need to set properties.security.protocol to SASL_SSL, properties.sasl.mechanism to GSSAPI or PLAIN, and properties.sasl.jaas.config to org.apache.kafka.common.security.plain.PlainLoginModule required username=\"xxx\" password=\"xxx\";.
krb_auth_name	No	None	String	Name of datasource authentication of the Kerberos type created on DLI. This configuration is used when SASL is configured for Kafka. Note: If the SASL_PLAINTEXT type and Kerberos authentication are used, you need to set properties.sasl.mechanism to GSSAPI and properties.security.protocol to SASL_PLAINTEXT.

Example (SASL_SSL Disabled for the Kafka Cluster)

In this example, data is read from a Kafka topic and written to another using a Kafka result table.

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.
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.

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 kafkaSource (
  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
) WITH (
  'connector' = 'kafka',
  'topic' = 'KafkaTopic',
  'properties.bootstrap.servers' = 'KafkaAddress1:KafkaPort,KafkaAddress2:KafkaPort',
  'properties.group.id' = 'GroupId',
  'scan.startup.mode' = 'latest-offset',
  "format" = "json"
);

CREATE TABLE kafkaSink (
  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
) WITH (
  'connector' = 'kafka',
  'topic' = 'KafkaSinkTopic',
  'properties.bootstrap.servers' = 'KafkaAddress1:KafkaPort,KafkaAddress2:KafkaPort',
  "format" = "json"
);

insert into kafkaSink select * from kafkaSource;

Connect to the Kafka cluster and insert the following test data into the source topic in Kafka:

{"order_id":"202103241000000001","order_channel":"webShop","order_time":"2021-03-24 10:00:00","pay_amount":100.0,"real_pay":100.0,"pay_time":"2021-03-24 10:02:03","user_id":"0001","user_name":"Alice","area_id":"330106"}

{"order_id":"202103241606060001","order_channel":"appShop","order_time":"2021-03-24 16:06:06","pay_amount":200.0,"real_pay":180.0,"pay_time":"2021-03-24 16:10:06","user_id":"0001","user_name":"Alice","area_id":"330106"}

Connect to the Kafka cluster and read data from the sink topic of Kafka.

{"order_id":"202103241000000001","order_channel":"webShop","order_time":"2021-03-24 10:00:00","pay_amount":100.0,"real_pay":100.0,"pay_time":"2021-03-24 10:02:03","user_id":"0001","user_name":"Alice","area_id":"330106"}

{"order_id":"202103241606060001","order_channel":"appShop","order_time":"2021-03-24 16:06:06","pay_amount":200.0,"real_pay":180.0,"pay_time":"2021-03-24 16:10:06","user_id":"0001","user_name":"Alice","area_id":"330106"}

Example (SASL_SSL Enabled for the Kafka Cluster)

Example 1: Enable SASL_SSL authentication for the DMS cluster.

Create a Kafka cluster for DMS, enable SASL_SSL, download the SSL certificate, and upload the downloaded certificate client.jks to an OBS bucket.

CREATE TABLE ordersSource (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:9093,xx:9093,xx:9093',
  'properties.group.id' = 'GroupId',
  'scan.startup.mode' = 'latest-offset',
  'properties.connector.auth.open' = 'true',
  'properties.ssl.truststore.location' = 'obs://xx/xx.jks',  -- Location where the user uploads the certificate to
  'properties.sasl.mechanism' = 'PLAIN',  --  Value format: SASL_PLAINTEXT
  'properties.security.protocol' = 'SASL_SSL',
  'properties.sasl.jaas.config' = 'org.apache.kafka.common.security.plain.PlainLoginModule required username=\"xx\" password=\"xx\";', -- Account and password set when the Kafka cluster is created
  "format" = "json"
);
 
CREATE TABLE ordersSink (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:9093,xx:9093,xx:9093',
  'properties.connector.auth.open' = 'true',
  'properties.ssl.truststore.location' = 'obs://xx/xx.jks',
  'properties.sasl.mechanism' = 'PLAIN',
  'properties.security.protocol' = 'SASL_SSL',
  'properties.sasl.jaas.config' = 'org.apache.kafka.common.security.plain.PlainLoginModule required username=\"xx\" password=\"xx\";',
  "format" = "json"
);
 
insert into ordersSink select * from ordersSource;

Example 2: Enable Kafka SASL_SSL authentication for the MRS cluster.

Enable Kerberos authentication for the MRS cluster.
Click the Components tab and click Kafka. In the displayed page, click the Service Configuration tab, locate the security.protocol, and set it to SASL_SSL.
Download the user credential. Log in to the FusionInsight Manager of the MRS cluster and choose System > Permission > User. Locate the row that contains the target user, click More, and select Download Authentication Credential.
Obtain the truststore.jks file using the authentication credential and store the credential and truststore.jks file in OBS.
If "Message stream modified (41)" is displayed, the JDK version may be incorrect. Change the JDK version in the sample code to a version earlier than 8u_242 or delete the renew_lifetime = 0m configuration item from the krb5.conf configuration file.
Set the port to the sasl_ssl.port configured in the Kafka service configuration.
In the following statements, set security.protocol to SASL_SSL.

CREATE TABLE ordersSource (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:21009,xx:21009',
  'properties.group.id' = 'GroupId',
  'scan.startup.mode' = 'latest-offset',
  'properties.sasl.kerberos.service.name' = 'kafka',
  'properties.connector.auth.open' = 'true',
  'properties.connector.kerberos.principal' = 'xx', --Username
  'properties.connector.kerberos.krb5' = 'obs://xx/krb5.conf',
  'properties.connector.kerberos.keytab' = 'obs://xx/user.keytab',
  'properties.security.protocol' = 'SASL_SSL',
  'properties.ssl.truststore.location' = 'obs://xx/truststore.jks',
  'properties.ssl.truststore.password' = 'xx',  -- Password set for generating truststore.jks
  'properties.sasl.mechanism' = 'GSSAPI',
  "format" = "json"
);
 
CREATE TABLE ordersSink (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:21009,xx:21009',
  'properties.sasl.kerberos.service.name' = 'kafka',
  'properties.connector.auth.open' = 'true',
  'properties.connector.kerberos.principal' = 'xx',
  'properties.connector.kerberos.krb5' = 'obs://xx/krb5.conf',
  'properties.connector.kerberos.keytab' = 'obs://xx/user.keytab',
  'properties.ssl.truststore.location' = 'obs://xx/truststore.jks',
  'properties.ssl.truststore.password' = 'xx',
  'properties.security.protocol' = 'SASL_SSL',
  'properties.sasl.mechanism' = 'GSSAPI',
  "format" = "json"
);
 
insert into ordersSink select * from ordersSource;

Example 3: Enable Kerberos SASL_PAINTEXT authentication for the MRS cluster

Enable Kerberos authentication for the MRS cluster.
Click the Components tab and click Kafka. In the displayed page, click the Service Configuration tab, locate the security.protocol, and set it to SASL_PLAINTEXT.
Log in to the FusionInsight Manager of the MRS cluster and download the user credential. Choose System > Permission > User. Locate the row that contains the target user, choose More > Download Authentication Credential. Upload the credential to OBS.
If error message "Message stream modified (41)" is displayed, the JDK version may be incorrect. Change the JDK version in the sample code to a version earlier than 8u_242 or delete the renew_lifetime = 0m configuration item from the krb5.conf configuration file.
Set the port to the sasl.port configured in the Kafka service configuration.
In the following statements, set security.protocol to SASL_PLAINTEXT.

CREATE TABLE ordersSources (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:21007,xx:21007',
  'properties.group.id' = 'GroupId',
  'scan.startup.mode' = 'latest-offset',
  'properties.sasl.kerberos.service.name' = 'kafka',
  'properties.connector.auth.open' = 'true',
  'properties.connector.kerberos.principal' = 'xx',
  'properties.connector.kerberos.krb5' = 'obs://xx/krb5.conf',
  'properties.connector.kerberos.keytab' = 'obs://xx/user.keytab',
  'properties.security.protocol' = 'SASL_PLAINTEXT',
  'properties.sasl.mechanism' = 'GSSAPI',
  "format" = "json"
);
 
CREATE TABLE ordersSink (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:21007,xx:21007',
  'properties.sasl.kerberos.service.name' = 'kafka',
  'properties.connector.auth.open' = 'true',
  'properties.connector.kerberos.principal' = 'xx',
  'properties.connector.kerberos.krb5' = 'obs://xx/krb5.conf',
  'properties.connector.kerberos.keytab' = 'obs://xx/user.keytab',
  'properties.security.protocol' = 'SASL_PLAINTEXT',
  'properties.sasl.mechanism' = 'GSSAPI',
  "format" = "json"
);
 
insert into ordersSink select * from ordersSource;

Example 4: Use SSL for the MRS cluster

Do not enable Kerberos authentication for the MRS cluster.
Download the user credential. Log in to the FusionInsight Manager of the MRS cluster and choose System > Permission > User. Locate the row that contains the target user, click More, and select Download Authentication Credential.
Obtain the truststore.jks file using the authentication credential and store the credential and truststore.jks file in OBS.
Set the port to the ssl.port configured in the Kafka service configuration.
In the following statements, set security.protocol to SSL.

Set ssl.mode.enable to true.

CREATE TABLE ordersSource (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'kafka',
  'topic' = 'xx',
  'properties.bootstrap.servers' = 'xx:9093,xx:9093,xx:9093',
  'properties.group.id' = 'GroupId',
  'scan.startup.mode' = 'latest-offset',
  'properties.connector.auth.open' = 'true',
  'properties.ssl.truststore.location' = 'obs://xx/truststore.jks',
  'properties.ssl.truststore.password' = 'xx',  -- Password set for generating truststore.jks
  'properties.security.protocol' = 'SSL',
  "format" = "json"
);
 
CREATE TABLE ordersSink (
  order_id string,
  order_channel string,
  order_time timestamp(3),
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id string
) WITH (
  'connector' = 'print'
);
 
insert into ordersSink select * from ordersSource;

Parent topic: Creating Result Tables

Previous topic: JDBC Result Table

Next topic: Print Result Table