Accessing a Kafka Instance Without SASL

This section describes how to use an open-source Kafka client to access a Kafka instance if SASL access is not enabled for the instance. There are two scenarios. For cross-VPC access, see Cross-VPC Access to a Kafka Instance. For DNAT-based access, see Using DNAT to Access a Kafka Instance.

For details on how to use Kafka clients in different languages, visit https://cwiki.apache.org/confluence/display/KAFKA/Clients.

The following describes the procedure for accessing a Kafka instance using CLI. To access an instance in your service code, see the Developer Guide.
For instances purchased in July 2020 and later, each Kafka broker allows a maximum of 1000 connections from each IP address by default. For instances purchased before July 2020, each Kafka broker allows a maximum of 200 connections from each IP address by default. Excess connections will be rejected. You can change the limit by referring to Modifying Kafka Parameters.

Prerequisites

Security group rules have been properly configured.
To access a Kafka instance with SASL disabled, configure proper security group rules. For details about security group configuration requirements, see Table 2.
The instance connection address has been obtained.
- For intra-VPC access, use port 9092. Obtain the instance connection address in the Connection section of the Basic Information tab page.
  Figure 1 Kafka instance connection addresses for intra-VPC access without SASL (in regions except CN North-Beijing4, CN East-Shanghai1, and CN South-Guangzhou)
  
  Figure 2 Kafka instance connection addresses for intra-VPC access without SASL (in regions CN North-Beijing4, CN East-Shanghai1, and CN South-Guangzhou)
- For public access, use port 9094. Obtain the instance connection address in the Connection section of the Basic Information tab page.
  Figure 3 Kafka instance connection addresses for public access without SASL (in regions except CN North-Beijing4, CN East-Shanghai1, and CN South-Guangzhou)
  
  Figure 4 Kafka instance connection addresses for public access without SASL (in regions CN North-Beijing4, CN East-Shanghai1, and CN South-Guangzhou)
If automatic topic creation is not enabled for the Kafka instance, create a topic before connecting to the instance.
Kafka CLI v1.1.0, v2.3.0,, or v2.7.2 is available. Ensure that the Kafka instance and the CLI use the same version.
An ECS has been created. For intra-VPC access, ensure that its VPC, subnet, and security group configurations are the same as those of the Kafka instance. JDK v1.8.111 or later has been installed on the ECS, and the JAVA_HOME and PATH environment variables have been configured as follows:
Add the following lines to the .bash_profile file in the home directory as an authorized user. In this command, /opt/java/jdk1.8.0_151 is the JDK installation path. Change it to the path where you install JDK.
```
export JAVA_HOME=/opt/java/jdk1.8.0_151 
export PATH=$JAVA_HOME/bin:$PATH
```
Run the source .bash_profile command for the modification to take effect.

Accessing the Instance Using CLI

The following uses Linux as an example.

Decompress the Kafka CLI package.
Access the directory where the CLI package is stored and run the following command to decompress the package:

tar -zxf [kafka_tar]

In the preceding command, [kafka_tar] indicates the name of the CLI package.

For example:

tar -zxf kafka_2.12-2.7.2.tgz
Access the /bin directory of the Kafka CLI.
In Windows, you need to access the /bin/windows directory.
Run the following command to create messages:
```
./kafka-console-producer.sh --broker-list ${connection-address} --topic ${topic-name}
```
Parameter description:
- {connection-address}: the address obtained in Prerequisites. For public access, use Instance Address (Public Network)/Address (Public Network, Plaintext). For intra-VPC access, use Instance Address (Private Network)/Address (Private Network, Plaintext).
- {topic-name}: the name of the topic created for the Kafka instance. If automatic topic creation has enabled for the Kafka instance, set this parameter to the name of a created topic or a topic that has not been created.
The following example uses connection addresses 10.xx.xx.45:9094,10.xx.xx.127:9094,10.xx.xx.103:9094. After running the preceding command, you can send a message to the Kafka instance by writing it and pressing Enter. Each line of content is sent as a message.
```
[root@ecs-kafka bin]# ./kafka-console-producer.sh --broker-list 10.xx.xx.45:9094,10.xx.xx.127:9094,10.xx.xx.103:9094  --topic topic-demo
>Hello
>DMS
>Kafka!
>^C[root@ecs-kafka bin]# 
```
To stop creating messages, press Ctrl+C to exit.
Run the following command to retrieve messages:
```
./kafka-console-consumer.sh --bootstrap-server ${connection-address} --topic ${topic-name} --group ${consumer-group-name} --from-beginning
```
Parameter description:
- {connection-address}: the address obtained in Prerequisites. For public access, use Instance Address (Public Network)/Address (Public Network, Plaintext). For intra-VPC access, use Instance Address (Private Network)/Address (Private Network, Plaintext).
- {topic-name}: the name of the topic created for the Kafka instance
- {consumer-group-name}: the consumer group name set based on your service requirements. If a consumer group name has been specified in the configuration file, ensure that you use the same name in the command line. Otherwise, consumption may fail. If a consumer group name starts with a special character, such as a number sign (#), the monitoring data cannot be displayed.
Example:
```
[root@ecs-kafka bin]#  ./kafka-console-consumer.sh --bootstrap-server 10.xx.xx.45:9094,10.xx.xx.127:9094,10.xx.xx.103:9094 --topic topic-demo --group order-test --from-beginning
Kafka!
DMS
Hello
^CProcessed a total of 3 messages
[root@ecs-kafka bin]# 
```
To stop retrieving messages, press Ctrl+C to exit.