Confluent 5.0 连接JDBC遇到的问题

大家好，我是一拳背A柱大弯的男人

这个礼拜直接原地爆炸，本周需要搭建Confluent平台并且通过JDBC连接数据源。我选择连接MySQL进行测试，但是在配置过程中遇到了问题，接下来我给大家讲一下我遇到的问题。

接下来我将详细汇报一下目前遇到的问题。

经过查询 Confluent 的文档我找到 Getting Started with Kafka Connect 这份用户手册，里面介绍了 Kafka Connect 能够连接多种数据源，并且可以在单机和集群模式下工作。

在单机模式下，只需要配置 worker.properties 和 connector.properties 两个配置文件即可启动：

bin/connect-standalone worker.properties connector1.properties [connector2.properties connector3.properties ...]

其中 worker.properties 文件用于配置kafka集群、序列化格式等配置；另一份文件 connector.properties 是连接器的配置文件，即配置连接不同数据源所需要的参数。

下面是我的两份配置文件：

connect-avro-standalone_my.properties

# Sample configuration for a standalone Kafka Connect worker that uses Avro serialization and
# integrates the the Schema Registry. This sample configuration assumes a local installation of
# Confluent Platform with all services running on their default ports.

# Bootstrap Kafka servers. If multiple servers are specified, they should be comma-separated.
bootstrap.servers=spark-02:9092,spark-03:9092,spark-04:9092

# The converters specify the format of data in Kafka and how to translate it into Connect data.
# Every Connect user will need to configure these based on the format they want their data in
# when loaded from or stored into Kafka
key.converter=io.confluent.connect.avro.AvroConverter
key.converter.schema.registry.url=http://localhost:8081
value.converter=io.confluent.connect.avro.AvroConverter
value.converter.schema.registry.url=http://localhost:8081

# The internal converter used for offsets and config data is configurable and must be specified,
# but most users will always want to use the built-in default. Offset and config data is never
# visible outside of Connect in this format.
internal.key.converter=org.apache.kafka.connect.json.JsonConverter
internal.value.converter=org.apache.kafka.connect.json.JsonConverter
internal.key.converter.schemas.enable=false
internal.value.converter.schemas.enable=false

# Local storage file for offset data
offset.storage.file.filename=/tmp/connect.offsets

# Confluent Control Center Integration -- uncomment these lines to enable Kafka client interceptors
# that will report audit data that can be displayed and analyzed in Confluent Control Center
# producer.interceptor.classes=io.confluent.monitoring.clients.interceptor.MonitoringProducerInterceptor
# consumer.interceptor.classes=io.confluent.monitoring.clients.interceptor.MonitoringConsumerInterceptor

# These are provided to inform the user about the presence of the REST host and port configs
# Hostname & Port for the REST API to listen on. If this is set, it will bind to the interface used to listen to requests.
#rest.host.name=
#rest.port=8083

# The Hostname & Port that will be given out to other workers to connect to i.e. URLs that are routable from other servers.
#rest.advertised.host.name=
#rest.advertised.port=

# Set to a list of filesystem paths separated by commas (,) to enable class loading isolation for plugins
# (connectors, converters, transformations). The list should consist of top level directories that include
# any combination of

source-kafka-jdbc-mysql.properties

这个文件中我配置了MySQL相关的内容。

# name 作为唯一标识
name=source-kafka-jdbc-mysql
# connector连接器配置，要求必须是org.apache.kafka.connect.connector.Connector的子类
connector.class=io.confluent.connect.jdbc.JdbcSourceConnector
# connector最大的任务数
tasks.max=1
# 需要查询的表
table.whitelist=t_sparksql1
# 下面是MySQL相关的配置连接
connection.url=jdbc:mysql://1.19.5.2:3306/sparkdb
connection.user=otoo
connection.password=osxw
# 查询的模式使用时间戳模式
mode=timestamp
# topic会根据表名自动生成，prefix是topic的前缀
topic.prefix=test-kafka-jdbc-mysql-
# 本次启动相关的jar包路径
plugin.path=/root/apps/confluent-5.0.0/share/java/kafka-connect-jdbc-my

plugin.path下的相关jar包

common-utils-6.0.0.jar         sqlite-jdbc-3.25.2.jar
oraclepki-19.7.0.0.jar  	   postgresql-42.2.10.jar  
ucp-19.7.0.0.jar               xdb-19.7.0.0.jar
jtds-1.3.1.jar                 ojdbc8-19.7.0.0.jar                  
orai18n-19.7.0.0.jar           simplefan-19.7.0.0.jar  
kafka-connect-jdbc-10.0.1.jar  ojdbc8-production-19.7.0.0.pom       
osdt_cert-19.7.0.0.jar         slf4j-api-1.7.30.jar    
xmlparserv2-19.7.0.0.jar       mssql-jdbc-8.4.1.jre8.jar      
ons-19.7.0.0.jar               osdt_core-19.7.0.0.jar  

这些jar包是在Confluent的Install the connector manually里找到的，我分别尝试了10.0、5.5、5.0三个版本，以上是10.0版本的相关jar包内容。

完成上述两个文件的配置后，启动服务：

./connect-standalone /root/apps/confluent-5.0.0/etc/schema-registry/connect-avro-standalone_my.properties /root/apps/confluent-5.0.0/etc/kafka-connect-jdbc/source-kafka-jdbc-mysql.properties

此时控制台将输出大量日志，在这些日志中报错的地方是下面这一段：

[2020-12-01 08:55:50,052] INFO Unable to connect to database on attempt 1/3. Will retry in 10000 ms. (io.confluent.connect.jdbc.util.CachedConnectionProvider:89)
java.sql.SQLException: No suitable driver found for jdbc:mysql://10.129.225.254:3306/sparkdb
	at java.sql.DriverManager.getConnection(DriverManager.java:689)
	at java.sql.DriverManager.getConnection(DriverManager.java:208)
	at io.confluent.connect.jdbc.dialect.GenericDatabaseDialect.getConnection(GenericDatabaseDialect.java:227)
	at io.confluent.connect.jdbc.util.CachedConnectionProvider.newConnection(CachedConnectionProvider.java:83)
	at io.confluent.connect.jdbc.util.CachedConnectionProvider.getConnection(CachedConnectionProvider.java:52)
	at io.confluent.connect.jdbc.JdbcSourceConnector.start(JdbcSourceConnector.java:92)
	at org.apache.kafka.connect.runtime.WorkerConnector.doStart(WorkerConnector.java:111)
	at org.apache.kafka.connect.runtime.WorkerConnector.start(WorkerConnector.java:136)
	at org.apache.kafka.connect.runtime.WorkerConnector.transitionTo(WorkerConnector.java:195)
	at org.apache.kafka.connect.runtime.Worker.startConnector(Worker.java:241)
	at org.apache.kafka.connect.runtime.standalone.StandaloneHerder.startConnector(StandaloneHerder.java:298)
	at org.apache.kafka.connect.runtime.standalone.StandaloneHerder.putConnectorConfig(StandaloneHerder.java:204)
	at org.apache.kafka.connect.cli.ConnectStandalone.main(ConnectStandalone.java:107)
[2020-12-01 08:56:00,054] INFO Attempting to open connection #2 to MySql (io.confluent.connect.jdbc.util.CachedConnectionProvider:82)

报错提示找不到合适的jdbc driver。

我在网上查资料，网友都说报这个错误应该是少了 mysql-connector-java 的jar包，于是我在MySQL的官方网站上找到了MySQL 5.7版本可用的jdbc版本：

Connector/J version	JDBC version	MySQL Server version	JRE Required	JDK Required for Compilation	Status
8.0	4.2 1	5.6, 5.7, 8.0	JRE 8 or higher	JDK 8.0 or higher3	General availability. Recommended version.
5.1	3.0, 4.0, 4.1, 4.2	5.62, 5.72, 8.02	JRE 5 or higher2	JDK 5.0 AND JDK 8.0 or higher3	General availability

​ 表格来源：Chapter 2 Connector/J Versions, and the MySQL and Java Versions They Require

经过两轮替换尝试还是报找不到driver这个错误。同时我在选择Kafka Connect JDBC的jar包集合的时候尝试换了10.0、5.50、5.0三个版本并且配合两个不同版本的connector尝试过，都没能正常启动服务。

总结

Confluent Platform是一个大集成平台，通过他可以配置很多服务，而目前我需要使用的有zookeeper和kafka。通过Confluent连接数据源有两种模式分别是Standalone和集群模式。通过Confluent官网的docs可以找到相关的配置信息，但是这次报的错误实在是不知道从何入手。接下来我打算还原Confluent平台重新配置kafka-connect-jdbc整个过程。