Chapter 3. Starting the services

Procedure

1. Start a MySQL database by running the following command, which starts a MySQL database server configured with an example inventory database:

   $ oc new-app -l app=mysql --name=mysql quay.io/debezium/example-mysql:latest

2. Configure credentials for the MySQL database by running the following command, which updates the deployment configuration for the MySQL database to add the user name and password:

   $ oc set env deployment/mysql MYSQL_ROOT_PASSWORD=debezium MYSQL_USER=mysqluser MYSQL_PASSWORD=mysqlpw

3. Verify that the MySQL database is running by invoking the following command, which is followed by the output that shows that the MySQL database is running, and that the pod is ready:

   $ oc get pods -l app=mysql
   NAME            READY   STATUS    RESTARTS   AGE
   mysql-1-2gzx5   1/1     Running   1          23s

4. Open a new terminal and log into the sample inventory database.

   This command opens a MySQL command line client in the pod that is running the MySQL database. The client uses the user name and password that you previously configured:

   $ oc exec mysql-1-2gzx5 -it -- mysql -u mysqluser -pmysqlpw inventory
   mysql: [Warning] Using a password on the command line interface can be insecure.
   Reading table information for completion of table and column names
   You can turn off this feature to get a quicker startup with -A
   
   Welcome to the MySQL monitor.  Commands end with ; or \g.
   Your MySQL connection id is 7
   Server version: 5.7.29-log MySQL Community Server (GPL)
   
   Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
   
   Oracle is a registered trademark of Oracle Corporation and/or its
   affiliates. Other names may be trademarks of their respective
   owners.
   
   Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
   
   mysql>

5. List the tables in the inventory database:

   mysql> show tables;
   +---------------------+
   | Tables_in_inventory |
   +---------------------+
   | addresses           |
   | customers           |
   | geom                |
   | orders              |
   | products            |
   | products_on_hand    |
   +---------------------+
   6 rows in set (0.00 sec)

6. Explore the database and view the data that it contains, for example, view the customers table:

   mysql> select * from customers;
   +------+------------+-----------+-----------------------+
   | id   | first_name | last_name | email                 |
   +------+------------+-----------+-----------------------+
   | 1001 | Sally      | Thomas    | sally.thomas@acme.com |
   | 1002 | George     | Bailey    | gbailey@foobar.com    |
   | 1003 | Edward     | Walker    | ed@walker.com         |
   | 1004 | Anne       | Kretchmar | annek@noanswer.org    |
   +------+------------+-----------+-----------------------+
   4 rows in set (0.00 sec)

Procedure

1. Log in to the OpenShift cluster and create or open a project, for example debezium.

2. Create a Debezium KafkaConnect custom resource (CR) for the connector, or modify an existing one.
   The following example shows an excerpt from a dbz-connect.yaml file that describes a KafkaConnect custom resource.
   The metadata.annotations and spec.build properties are required.

   Example 3.1. A dbz-connect.yaml file that defines a KafkaConnect custom resource that includes a Debezium connector

   apiVersion: kafka.strimzi.io/v1beta2
   kind: KafkaConnect
   metadata:
     name: my-connect-cluster
     annotations:
       strimzi.io/use-connector-resources: "true" 1
   spec:
     replicas: 1
     version: 3.6.0
     build: 2
       output: 3
         type: imagestream  4
         image: debezium-streams-connect:latest
       plugins: 5
         - name: debezium-connector-mysql
           artifacts:
             - type: zip 6
               url: https://maven.repository.redhat.com/ga/io/debezium/debezium-connector-mysql/2.7.3.Final-redhat-00001/debezium-connector-mysql-2.7.3.Final-redhat-00001-plugin.zip 7
     bootstrapServers: my-cluster-kafka-bootstrap:9093
   
   ...

   Table 3.1. Descriptions of Kafka Connect configuration settings

   Item	Description
   1	Sets the strimzi.io/use-connector-resources annotation to "true" to enable the Cluster Operator to use KafkaConnector resources to configure connectors in this Kafka Connect cluster.
   2	The spec.build configuration specifies where to store the build image and lists the plug-ins to include in the image, along with the location of the plug-in artifacts.
   3	The build.output specifies the registry in which the newly built image is stored.
   4	Specifies the name and image name for the image output. Valid values for output.type are docker to push into a container registry like Docker Hub or Quay, or imagestream to push the image to an internal OpenShift ImageStream. To use an ImageStream, an ImageStream resource must be deployed to the cluster. For more information about specifying the build.output in the KafkaConnect configuration, see the Streams for Apache Kafka Build schema reference documentation.
   5	The plugins configuration lists all of the connectors that you want to include in the Kafka Connect image. For each entry in the list, specify a plug-in name, and information for about the artifacts that are required to build the connector. Optionally, for each connector plug-in, you can include other components that you want to be available for use with the connector. For example, you can add Service Registry artifacts, or the Debezium scripting component.
   6	The value of artifacts.type specifies the file type of the artifact specified in the artifacts.url. Valid types are zip, tgz, or jar. Debezium connector archives are provided in .zip file format. JDBC driver files are in .jar format. The type value must match the type of the file that is referenced in the url field.
   7	The value of artifacts.url specifies the address of an HTTP server, such as a Maven repository, that stores the file for the connector artifact. The OpenShift cluster must have access to the specified server.

3. Apply the KafkaConnect build specification to the OpenShift cluster by entering the following command:

   oc create -f dbz-connect.yaml

   Based on the configuration specified in the custom resource, the Streams for Apache Kafka Operator prepares a Kafka Connect image to deploy.
   After the build completes, the Operator pushes the image to the specified registry or ImageStream, and starts the Kafka Connect cluster. The connector artifacts that you listed in the configuration are available in the cluster.

4. Create a KafkaConnector resource to define an instance of the MySQL connector.
   For example, create the following KafkaConnector CR, and save it as debezium-inventory-connector.yaml

   Example 3.2. A mysql-inventory-connector.yaml file that defines the KafkaConnector custom resource for a Debezium connector

   apiVersion: kafka.strimzi.io/v1beta2
   kind: KafkaConnector
   metadata:
     labels:
       strimzi.io/cluster: my-connect-cluster
     name: inventory-connector 1
   spec:
     class: io.debezium.connector.mysql.MySqlConnector 2
     tasksMax: 1  3
     config:  4
       database.hostname: mysql 5
       database.port: 3306   6
       database.user: debezium  7
       database.password: dbz  8
       database.server.id: 184054
       topic.prefix: dbserver1  9
       table.include.list: inventory.*  10
       schema.history.internal.kafka.bootstrap.servers: 'my-cluster-kafka-bootstrap:9092' 11
       schema.history.internal.kafka.topic: schema-changes.inventory 12

   Table 3.2. Descriptions of connector configuration settings

   Item	Description
   1	The name of the connector to register with the Kafka Connect cluster.
   2	The name of the connector class.
   3	Only one task should operate at any one time. Use a single connector task to ensure proper order and event handling as the MySQL connector reads the MySQL server’s binlog. The Kafka Connect service uses connectors to start one or more tasks to complete the work. It automatically distributes the running tasks across the cluster of Kafka Connect services. If services stop or crash, tasks are redistributed to running services.
   4	The connector’s configuration.
   5	The hostname or address of the MySQL database instance.
   6	The port number of the database instance.
   7	The name of the user account through which Debezium connects to the database.
   8	The password that Debezium uses to connect to the database user account.
   9	Topic prefix for the MySQL server or cluster. This string prefixes the names of every Kafka topic that the connector sends event records to.
   10	The list of tables from which the connector captures change events. The connector detects changes only if they occur in the inventory table.
   11	List of Kafka brokers that the connector uses to write and recover DDL statements to the database schema history topic. This is the same broker that the connector sends change event records to. After a restart, the connector recovers the database schemas that existed at the point in the binlog when the connector resumes reading.
   12	Name of the database schema history topic. This topic is for internal use only and should not be used by consumers.

5. Create the connector resource by running the following command:

   oc create -n <namespace> -f <kafkaConnector>.yaml

   For example,

   oc create -n debezium -f mysql-inventory-connector.yaml

   The connector is registered to the Kafka Connect cluster and starts to run against the database that is specified by spec.config.database.dbname in the KafkaConnector CR. After the connector pod is ready, Debezium is running.

Procedure

1. Check the status of the KafkaConnector resource by using one of the following methods:

   • From the OpenShift Container Platform web console:

     1. Navigate to Home Search.
     2. On the Search page, click Resources to open the Select Resource box, and then type KafkaConnector.
     3. From the KafkaConnectors list, click the name of the connector that you want to check, for example inventory-connector.
     4. In the Conditions section, verify that the values in the Type and Status columns are set to Ready and True.

   • From a terminal window:

     1. Enter the following command:

        oc describe KafkaConnector <connector-name> -n <project>

        For example,

        oc describe KafkaConnector inventory-connector -n debezium

        The command returns status information that is similar to the following output:

        Example 3.3. KafkaConnector resource status

        Name:         inventory-connector
        Namespace:    debezium
        Labels:       strimzi.io/cluster=my-connect-cluster
        Annotations:  <none>
        API Version:  kafka.strimzi.io/v1beta2
        Kind:         KafkaConnector
        
        ...
        
        Status:
          Conditions:
            Last Transition Time:  2021-12-08T17:41:34.897153Z
            Status:                True
            Type:                  Ready
          Connector Status:
            Connector:
              State:      RUNNING
              worker_id:  10.131.1.124:8083
            Name:         inventory-connector
            Tasks:
              Id:               0
              State:            RUNNING
              worker_id:        10.131.1.124:8083
            Type:               source
          Observed Generation:  1
          Tasks Max:            1
          Topics:
            dbserver1
            dbserver1.inventory.addresses
            dbserver1.inventory.customers
            dbserver1.inventory.geom
            dbserver1.inventory.orders
            dbserver1.inventory.products
            dbserver1.inventory.products_on_hand
        Events:  <none>

2. Verify that the connector created Kafka topics:

   • From the OpenShift Container Platform web console.

     1. Navigate to Home Search.
     2. On the Search page, click Resources to open the Select Resource box, and then type KafkaTopic.
     3. From the KafkaTopics list, click the name of the topic that you want to check, for example, dbserver1.inventory.orders---ac5e98ac6a5d91e04d8ec0dc9078a1ece439081d.
     4. In the Conditions section, verify that the values in the Type and Status columns are set to Ready and True.

   • From a terminal window:

     1. Enter the following command:

        oc get kafkatopics

        The command returns status information that is similar to the following output:

        Example 3.4. KafkaTopic resource status

        NAME                   CLUSTER  PARTITIONS  REPLICATION FACTOR  READY
        connect-cluster-configs  my-cluster   1        1            True
        connect-cluster-offsets  my-cluster   25       1            True
        connect-cluster-status   my-cluster   5        1            True
        consumer-offsets---84e7a678d08f4bd226872e5cdd4eb527fadc1c6a my-cluster 50 1 True
        dbserver1---a96f69b23d6118ff415f772679da623fbbb99421 my-cluster 1 1 True
        dbserver1.inventory.addresses---1b6beaf7b2eb57d177d92be90ca2b210c9a56480  my-cluster 1 1 True
        dbserver1.inventory.customers---9931e04ec92ecc0924f4406af3fdace7545c483b  my-cluster 1 1   True
        dbserver1.inventory.geom---9f7e136091f071bf49ca59bf99e86c713ee58dd5  my-cluster 1 1   True
        dbserver1.inventory.orders---ac5e98ac6a5d91e04d8ec0dc9078a1ece439081d my-cluster 1 1   True
        dbserver1.inventory.products---df0746db116844cee2297fab611c21b56f82dcef my-cluster 1 1   True
        dbserver1.inventory.products-on-hand---8649e0f17ffcc9212e266e31a7aeea4585e5c6b5  my-cluster 1  1 True
        schema-changes.inventory my-cluster    1           1       True
        strimzi-store-topic---effb8e3e057afce1ecf67c3f5d8e4e3ff177fc55                  my-cluster   1    1  True
        strimzi-topic-operator-kstreams-topic-store-changelog---b75e702040b99be8a9263134de3507fc0cc4017b my-cluster 1    1  True

3. Check topic content.

   • From a terminal window, enter the following command:

   oc exec -n <project>  -it <kafka-cluster> -- /opt/kafka/bin/kafka-console-consumer.sh \
   >     --bootstrap-server localhost:9092 \
   >     --from-beginning \
   >     --property print.key=true \
   >     --topic=<topic-name>

   For example,

    oc exec -n debezium  -it my-cluster-kafka-0 -- /opt/kafka/bin/kafka-console-consumer.sh \
   >     --bootstrap-server localhost:9092 \
   >     --from-beginning \
   >     --property print.key=true \
   >     --topic=dbserver1.inventory.products_on_hand

   The format for specifying the topic name is the same as the oc describe command returns in Step 1, for example, dbserver1.inventory.addresses.

   For each event in the topic, the command returns information that is similar to the following output:

   Example 3.5. Content of a Debezium change event

   {"schema":{"type":"struct","fields":[{"type":"int32","optional":false,"field":"product_id"}],"optional":false,"name":"dbserver1.inventory.products_on_hand.Key"},"payload":{"product_id":101}}	{"schema":{"type":"struct","fields":[{"type":"struct","fields":[{"type":"int32","optional":false,"field":"product_id"},{"type":"int32","optional":false,"field":"quantity"}],"optional":true,"name":"dbserver1.inventory.products_on_hand.Value","field":"before"},{"type":"struct","fields":[{"type":"int32","optional":false,"field":"product_id"},{"type":"int32","optional":false,"field":"quantity"}],"optional":true,"name":"dbserver1.inventory.products_on_hand.Value","field":"after"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"version"},{"type":"string","optional":false,"field":"connector"},{"type":"string","optional":false,"field":"name"},{"type":"int64","optional":false,"field":"ts_ms"},{"type":"string","optional":true,"name":"io.debezium.data.Enum","version":1,"parameters":{"allowed":"true,last,false"},"default":"false","field":"snapshot"},{"type":"string","optional":false,"field":"db"},{"type":"string","optional":true,"field":"sequence"},{"type":"string","optional":true,"field":"table"},{"type":"int64","optional":false,"field":"server_id"},{"type":"string","optional":true,"field":"gtid"},{"type":"string","optional":false,"field":"file"},{"type":"int64","optional":false,"field":"pos"},{"type":"int32","optional":false,"field":"row"},{"type":"int64","optional":true,"field":"thread"},{"type":"string","optional":true,"field":"query"}],"optional":false,"name":"io.debezium.connector.mysql.Source","field":"source"},{"type":"string","optional":false,"field":"op"},{"type":"int64","optional":true,"field":"ts_ms"},{"type":"struct","fields":[{"type":"string","optional":false,"field":"id"},{"type":"int64","optional":false,"field":"total_order"},{"type":"int64","optional":false,"field":"data_collection_order"}],"optional":true,"field":"transaction"}],"optional":false,"name":"dbserver1.inventory.products_on_hand.Envelope"},"payload":{"before":null,"after":{"product_id":101,"quantity":3},"source":{"version":"2.7.3.Final-redhat-00001","connector":"mysql","name":"dbserver1","ts_ms":1638985247805,"snapshot":"true","db":"inventory","sequence":null,"table":"products_on_hand","server_id":0,"gtid":null,"file":"mysql-bin.000003","pos":156,"row":0,"thread":null,"query":null},"op":"r","ts_ms":1638985247805,"transaction":null}}

   In the preceding example, the payload value shows that the connector snapshot generated a read ("op" ="r") event from the table dbserver1.products_on_hand. The "before" state of the product_id record is null, indicating that no previous value exists for the record. The "after" state shows a quantity of 3 for the item with product_id 101.