Debezium Adapt openGauss

原作者：李宏达

一、 What is Debezium

Debezium is a set of distributed services to capture changes in your databases so that your applications can see those changes and respond to them. Debezium records all row-level changes within each database table in a change event stream, and applications simply read these streams to see the change events in the same order in which they occurred.

二、 Introduction to Debezium

Debezium is a distributed platform that turns your existing databases into event streams, so applications can see and respond immediately to each row-level change in the databases.

Debezium is built on top of Apache Kafka and provides Kafka Connect compatible connectors that monitor specific database management systems. Debezium records the history of data changes in Kafka logs, from where your application consumes them. This makes it possible for your application to easily consume all of the events correctly and completely. Even if your application stops unexpectedly, it will not miss anything: when the application restarts, it will resume consuming the events where it left off.

Debezium includes multiple connectors.

• MongoDB
• MySQL
• PostgreSQL
• SQL Server
• Oracle (Incubating)
• Db2 (Incubating)
• Cassandra (Incubating)
• Vitess (Incubating)

三、 Debezium Features

Debezium is a set of source connectors for Apache Kafka Connect. Each connector ingests changes from a different database by using that database’s features for change data capture (CDC). Unlike other approaches, such as polling or dual writes, log-based CDC as implemented by Debezium:

• Ensures that all data changes are captured.
• Produces change events with a very low delay while avoiding increased CPU usage required for frequent polling. For example, for MySQL or PostgreSQL, the delay is in the millisecond range.
• Requires no changes to your data model, such as a “Last Updated” column.
• Can capture deletes.
• Can capture old record state and additional metadata such as transaction ID and causing query, depending on the database’s capabilities and configuration.

Five Advantages of Log-Based Change Data Capture is a blog post that provides more details.

Debezium connectors capture data changes with a range of related capabilities and options:

• Snapshots: optionally, an initial snapshot of a database’s current state can be taken if a connector is started and not all logs still exist. Typically, this is the case when the database has been running for some time and has discarded trannsaction logs that are no longer needed for transaction recovery or replication. There are different modes for performing snapshots. See the documentation for the connector that you are using.
• Filters: you can configure the set of captured schemas, tables and columns with include/exclude list filters.
• Masking: the values from specific columns can be masked, for example, when they contain sensitive data.
• Monitoring: most connectors can be monitored by using JMX.
• Ready-to-use message transformations for:
  • Message routing
  • Content-based routing
  • Extraction of new record state for relational connectors and for the MongoDB connector
  • Filtering
  • Routing of events from a transactional outbox table

四、 Adapt openGauss

1. openGauss postgreSQL wal2json的关系

• openGauss是一款开源关系型数据库管理系统，采用木兰宽松许可证v2发行。openGauss内核源自PostgreSQL，同时openGauss也是一个开源的数据库平台，鼓励社区贡献、合作。
• PostgreSQL是一种特性非常齐全的自由软件的对象-关系型数据库管理系统（ORDBMS），是以加州大学计算机系开发的POSTGRES，4.2版本为基础的对象关系型数据库管理系统。另外，因为许可证的灵活，任何人都可以以任何目的免费使用、修改和分发PostgreSQL。
• wal2json is an output plugin for logical decoding. It means that the plugin have access to tuples produced by INSERT and UPDATE. Also, UPDATE/DELETE old row versions can be accessed depending on the configured replica identity. Changes can be consumed using the streaming protocol (logical replication slots) or by a special SQL API.
  • format version 1 produces a JSON object per transaction. All of the new/old tuples are available in the JSON object. Also, there are options to include properties such as transaction timestamp, schema-qualified, data types, and transaction ids.
  • format version 2 produces a JSON object per tuple. Optional JSON object for beginning and end of transaction. Also, there are a variety of options to include properties.

openGauss为开源数据库PG for 9.2.4基础上deconding,wal2json为PG的日志解析插件，将wal日志解析成dml语句以json的形式输出。云和恩墨基于wal2json for pg将该插件适配openGauss即wal2json for openGauss.

• wal2json下载地址

五、 openGauss install wal2json

关于openGauss的安装可参考

• 一键安装
• 容器安装

1. 修改参数wal_level,添加hba

postgres=# alter system set wal_level = logical;
NOTICE: please restart the database for the POSTMASTER level parameter to take effect.
ALTER SYSTEM SET
[omm@0f0ce5be9d04 ~]$ echo "host replication gaussdb 0.0.0.0/0 md5" >> /var/lib/opengauss/data/pg_hba.conf
[omm@0f0ce5be9d04 ~]$ gs_ctl restart -D /var/lib/opengauss/data/
[2020-12-07 03:51:12.500][293][][gs_ctl]: gs_ctl restarted ,datadir is -D "/var/lib/opengauss/data"
waiting for server to shut down...


2. 上传wal2json

[omm@0f0ce5be9d04 ~]$ cd $GAUSSHOME/lib/postgresql
[omm@0f0ce5be9d04 postgresql]$ ls wal2json.so
wal2json.so


3. 测试wal2json

session 1

[omm@0f0ce5be9d04 data]$ pg_recvlogical --help
pg_recvlogical receives logical change stream.

[omm@0f0ce5be9d04 data]$ pg_recvlogical -d postgres -S test_wal2json --create -U gaussdb -h 172.24.0.2 -P wal2json
Password:


保持session1 终端

[omm@0f0ce5be9d04 data]$ pg_recvlogical -d postgres -S test_wal2json --start -U gaussdb -h 172.24.0.2 -o pretty-print=1 -f -
Password:
{
"change": [
{
"kind": "insert",
"schema": "gaussdb",
"table": "test",
"columnnames": ["id", "name"],
"columntypes": ["integer", "character varying(20)"],
"columnvalues": [4, "Beijing"]
}
]
}
{
"change": [
{
"kind": "update",
"schema": "gaussdb",
"table": "test",
"columnnames": ["id", "name"],
"columntypes": ["integer", "character varying(20)"],
"columnvalues": [4, "keji"],
"oldkeys": {
"keynames": ["id", "name"],
"keytypes": ["integer", "character varying(20)"],
"keyvalues": [4, "Beijing"]
}
}
]
}
{
"change": [
{
"kind": "delete",
"schema": "gaussdb",
"table": "test",
"oldkeys": {
"keynames": ["id", "name"],
"keytypes": ["integer", "character varying(20)"],
"keyvalues": [4, "keji"]
}
}
]
}


session 2 执行dml

[omm@0f0ce5be9d04 postgresql]$ gsql -d postgres -p5432 -r -Ugaussdb
Password for user gaussdb:
gsql ((openGauss 1.0.1 build 13b34b53) compiled at 2020-10-12 02:00:59 commit 0 last mr )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

postgres=> insert into test values(4,'Beijing');
INSERT 0 1
postgres=> update test set name='keji' where id=4;
UPDATE 1
postgres=> delete test where id=4;
DELETE 1
postgres=>


可以看到session1分别记录了三条dml语句

六、 Debeziun for openGauss adaptation process

本步骤为手动适配connect容器和配置文件过程(可不做)

1. 替换jar文件

• debezium-connector-postgres-1.4.0-SNAPSHOT.jar
• postgres.jar

[root@asianux debezium]# git clone https://github.com/debezium/debezium-examples.git

[root@asianux tutorial]# docker restart tutorial_connect_1


2. 编写配置文件

[root@asianux tutorial]# pwd
/opt/debezium/debezium-examples/tutorial

[root@asianux tutorial]# cat register-opengauss.json
{
"name": "inventory-connector1",
"config": {
"connector.class": "io.debezium.connector.postgresql.PostgresConnector",
"tasks.max": "1",
"database.hostname": "opengauss",
"database.port": "5432",
"database.user": "gaussdb",
"database.password": "Enmo@123",
"database.dbname" : "postgres",
"database.server.name": "dbserver1_opengauss",
"schema.include.list": "gaussdb",
"plugin.name": "wal2json",
"slot.name": "wal2json2"
}
}


七、 Debeziun for openGauss Installtion

1. 下载debeziun-example

git clone https://gitee.com/lee1002/debezium-examples

[root@asianux opt]# git clone https://gitee.com/lee1002/debezium-examples
Cloning into 'debezium-examples'...
remote: Enumerating objects: 3850, done.
remote: Counting objects: 100% (3850/3850), done.
remote: Compressing objects: 100% (1446/1446), done.
remote: Total 3850 (delta 1466), reused 3850 (delta 1466), pack-reused 0
Receiving objects: 100% (3850/3850), 5.59 MiB | 0 bytes/s, done.
Resolving deltas: 100% (1466/1466), done.


2. Start Container

docker-compose -f docker-compose-opengauss.yaml up -d

[root@asianux opt]# cd debezium-examples/tutorial/
[root@asianux tutorial]# docker-compose -f docker-compose-opengauss.yaml up -d
Creating tutorial_kafka_1 ... done
Creating tutorial_zookeeper_1 ...
Creating tutorial_kafka_1 ...
Creating tutorial_connect_1 ... done


3. Start openGauss connector

curl -i -X POST -H “Accept:application/json” -H “Content-Type:application/json” http://localhost:8083/connectors/ -d @register-opengauss.json

[root@asianux tutorial]# curl -i -X POST -H "Accept:application/json" -H "Content-Type:application/json" http://localhost:8083/connectors/ -d @register-opengauss.json
HTTP/1.1 201 Created
Date: Mon, 07 Dec 2020 06:30:40 GMT
Location: http://localhost:8083/connectors/inventory-connector1
Content-Type: application/json
Content-Length: 453
Server: Jetty(9.4.24.v20191120)
{"name":"inventory-connector1","config":{"connector.class":"io.debezium.connector.postgresql.PostgresConnector","tasks.max":"1","database.hostname":"opengauss","database.port":"5432","database.user":"gaussdb","database.password":"Enmo@123","database.dbname":"postgres","database.server.name":"dbserver1_opengauss","schema.include.list":"gaussdb","plugin.name":"wal2json","slot.name":"wal2json2","name":"inventory-connector1"},"tasks":[],"type":"source"}


4. Consume messages from a Debezium topic

docker-compose -f docker-compose-postgres.yaml exec kafka /kafka/bin/kafka-console-consumer.sh
–bootstrap-server kafka:9092
–from-beginning
–property print.key=true
–topic dbserver1_opengauss.gaussdb.test

[root@asianux tutorial]# docker-compose -f docker-compose-postgres.yaml exec kafka /kafka/bin/kafka-console-consumer.sh \
> --bootstrap-server kafka:9092 \
> --from-beginning \
> --property print.key=true \
> --topic dbserver1_opengauss.gaussdb.test

"payload":{"before":null,"after":{"id":1,"name":"yun"}
"payload":{"before":null,"after":{"id":2,"name":"he"}
"payload":{"before":null,"after":{"id":3,"name":"enmo"}


5. DML Test

session 1

[omm@a731769e567f ~]$ gsql -d postgres -p5432 -Ugaussdb -r
Password for user gaussdb:
gsql ((openGauss 1.0.1 build 13b34b53) compiled at 2020-10-12 02:00:59 commit 0 last mr )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

postgres=> insert into test values (4,'Beijing');
INSERT 0 1
postgres=> update test set name='keji' where id=4;
UPDATE 1
postgres=> delete test where id=4;
DELETE 1


session 2

[root@asianux tutorial]# docker-compose -f docker-compose-postgres.yaml exec kafka /kafka/bin/kafka-console-consumer.sh \
> --bootstrap-server kafka:9092 \
> --from-beginning \
> --property print.key=true \
> --topic dbserver1_opengauss.gaussdb.test

"payload":{"before":null,"after":{"id":1,"name":"yun"}
"payload":{"before":null,"after":{"id":2,"name":"he"}
"payload":{"before":null,"after":{"id":3,"name":"enmo"}
"payload":{"before":null,"after":{"id":4,"name":"Beijing"} --insert
"payload":{"before":{"id":4,"name":"Beijing"},"after":{"id":4,"name":"keji"} --update
"payload":{"before":{"id":4,"name":"keji"},"after":null --delete


6. Shut down the cluster

docker-compose -f docker-compose-opengauss.yaml down

[root@asianux tutorial]# docker-compose -f docker-compose-opengauss.yaml down
Stopping tutorial_connect_1 ... done
Stopping tutorial_kafka_1 ... done
Stopping tutorial_zookeeper_1 ... done
Stopping tutorial_opengauss_1 ... done
Removing tutorial_connect_1 ... done
Removing tutorial_kafka_1 ... done
Removing tutorial_zookeeper_1 ... done
Removing tutorial_opengauss_1 ... done
Removing network tutorial_default


• 原文链接
  http://www.lihongda.club/index.php/2020/12/07/debezium-adapt-opengauss/
• debezium官网
  https://debezium.io/
• debezium github
  https://github.com/debezium
• wal2json下载地址
  http://www.lihongda.club/wp-content/uploads/2020/12/wal2json.so
• 一键安装
  http://www.lihongda.club/index.php/2020/12/01/opengauss%e4%bb%8e%e6%ba%90%e7%a0%81%e5%88%b0%e8%87%aa%e5%8a%a8%e5%8c%96/
• 容器安装
  https://github.com/enmotech/enmotech-docker-opengauss
• connect组件 debezium-connector-postgres-1.4.0-SNAPSHOT.jar
  http://www.lihongda.club/wp-content/uploads/2020/12/debezium-connector-postgres-1.4.0-SNAPSHOT.jar
• connect组件 postgres.jar
  https://opengauss.obs.cn-south-1.myhuaweicloud.com/1.0.1/x86/openGauss-1.0.1-JDBC.tar.gz