我尝试将数据从kafka主题流式传输到mysql数据库，但没有成功。虽然 source connector 工作正常（即，将数据从mysql数据库流式传输到kafka主题）， sink connector 无法加载。
这是我的 sink-mysql.properties 文件：

name=sink-mysql
connector.class=io.confluent.connect.jdbc.JdbcSinkConnector
tasks.max=1
topics=test-mysql-jdbc-foobar
connection.url=jdbc:mysql://127.0.0.1:3306/demo?user=user1&password=user1pass
auto.create=true

当我试图执行

./bin/connect-standalone etc/schema-registry/connect-avro-standalone.properties etc/kafka-connect-jdbc/sink-mysql.properties

报告了以下错误：

[2018-02-01 16:17:43,019] ERROR WorkerSinkTask{id=sink-mysql-0} Task threw an uncaught and unrecoverable exception. Task is being killed and will not recover until manually restarted. (org.apache.kafka.connect.runtime.WorkerSinkTask:515)
org.apache.kafka.connect.errors.ConnectException: No fields found using key and value schemas for table: test-mysql-jdbc-foobar
    at io.confluent.connect.jdbc.sink.metadata.FieldsMetadata.extract(FieldsMetadata.java:127)
    at io.confluent.connect.jdbc.sink.metadata.FieldsMetadata.extract(FieldsMetadata.java:64)
    at io.confluent.connect.jdbc.sink.BufferedRecords.add(BufferedRecords.java:71)
    at io.confluent.connect.jdbc.sink.JdbcDbWriter.write(JdbcDbWriter.java:66)
    at io.confluent.connect.jdbc.sink.JdbcSinkTask.put(JdbcSinkTask.java:69)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.deliverMessages(WorkerSinkTask.java:495)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.poll(WorkerSinkTask.java:288)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.iteration(WorkerSinkTask.java:198)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:166)
    at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:170)
    at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:214)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
[2018-02-01 16:17:43,020] ERROR WorkerSinkTask{id=sink-mysql-0} Task threw an uncaught and unrecoverable exception (org.apache.kafka.connect.runtime.WorkerTask:172)
org.apache.kafka.connect.errors.ConnectException: Exiting WorkerSinkTask due to unrecoverable exception.
    at org.apache.kafka.connect.runtime.WorkerSinkTask.deliverMessages(WorkerSinkTask.java:517)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.poll(WorkerSinkTask.java:288)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.iteration(WorkerSinkTask.java:198)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:166)
    at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:170)
    at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:214)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.kafka.connect.errors.ConnectException: No fields found using key and value schemas for table: test-mysql-jdbc-foobar
    at io.confluent.connect.jdbc.sink.metadata.FieldsMetadata.extract(FieldsMetadata.java:127)
    at io.confluent.connect.jdbc.sink.metadata.FieldsMetadata.extract(FieldsMetadata.java:64)
    at io.confluent.connect.jdbc.sink.BufferedRecords.add(BufferedRecords.java:71)
    at io.confluent.connect.jdbc.sink.JdbcDbWriter.write(JdbcDbWriter.java:66)
    at io.confluent.connect.jdbc.sink.JdbcSinkTask.put(JdbcSinkTask.java:69)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.deliverMessages(WorkerSinkTask.java:495)
    ... 10 more
[2018-02-01 16:17:43,021] ERROR WorkerSinkTask{id=sink-mysql-0} Task is being killed and will not recover until manually restarted (org.apache.kafka.connect.runtime.WorkerTask:173)

注意这个主题 test-mysql-jdbc-foobar 包含从mysql到kafka的数据流，但是，我无法将这些数据从mysql流回到kafka。sink-mysql.properties的内容看起来与官方confluent文档中使用的内容相同，但似乎不起作用。另外，mysql connector被放置在正确的目录中（在 share/java/kafka-connect-jdbc/ ).
编辑
以下是我的worker配置文件的内容：

bootstrap.servers=localhost:9092
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

key.converter=org.apache.kafka.connect.json.JsonConverter
value.converter=org.apache.kafka.connect.json.JsonConverter
key.converter.schemas.enable=false
value.converter.schemas.enable=false

# Local storage file for offset data

offset.storage.file.filename=/tmp/connect.offsets

plugin.path=share/java