我的应用程序中的Kafka debezium-postgres连接器抛出此错误：
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版本9.6.11，max_replication_slots的值为10。我可以看到数据库中的活动逻辑replication_slot，其中confirmed_flush_lsn = null，restart_lsn = 3/93043310，catalog_xmin = 202656，active = t，datoid = 16407，slot_type =逻辑，active_pid = 32183，插件= wal2json，slot_name = slot1，数据库= db1（我已用虚拟值替换了插槽名称和数据库名称）根据我的理解，由于此处的逻辑复制插槽的Confirmed_flush_lsn = null导致此错误，因为它阻止连接器找到此插槽。
我该如何解决，为什么Confirmed_flush_lsn值将为null？