Postgresql kafka连接错误：无法获取有效的复制插槽

我的应用程序中的Kafka debezium postgres连接器引发以下错误：

org.apache.kafka.connect.errors.ConnectException: Unable to obtain valid replication slot. Make sure there are no long-running transactions running in parallel as they may hinder the allocation of the replication slot when starting this connector
    at io.debezium.connector.postgresql.connection.PostgresConnection.readReplicationSlotInfo(PostgresConnection.java:226)
    at io.debezium.connector.postgresql.connection.PostgresConnection.getReplicationSlotState(PostgresConnection.java:150)
    at io.debezium.connector.postgresql.PostgresConnectorTask.start(PostgresConnectorTask.java:98)
    at io.debezium.connector.common.BaseSourceTask.start(BaseSourceTask.java:49)
    at org.apache.kafka.connect.runtime.WorkerSourceTask.execute(WorkerSourceTask.java:198)
    at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:175)
    at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:219)
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)

该应用程序使用postgresql 9.6.11版，最大复制槽的值为10。我可以看到数据库中的活动逻辑复制插槽，已确认\u flush\u lsn=null，restart\u lsn=3/93043310，catalog\u xmin=202656，active=t，datoid=16407，slot\u type=logical，active\u pid=32183，plugin=wal2json，slot\u name=slot1，database=db1（我已经用伪值替换了插槽名称和数据库名称）
根据我的理解，因为此处的逻辑复制插槽已确认\u flush\u lsn=null，导致此错误，因为它阻止连接器找到此插槽

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我如何解决这个问题？为什么确认的\u flush\u lsn值将为空

我通过重新启动连接器引用的aws中的rds DB实例将其修复，之后确认的_flush_lsn值被重置为与（restart_lsn=3/93043310）类似的非空值。kafka connect能够按预期找到复制_插槽“slot1”。接头也被拔出。 这暂时解决了我的问题，但我仍然想了解，对于逻辑复制\u插槽，首先应该将什么设置为confirm\u flush\u lsn=null