RedisKeyRegistrationHandler: READONLY You can't write against a read only replica following Redis Sentinel failover

[quantranhong1999]

Why

Given Redis Sentinel mode, a master node is down, and failover is trigger: other Redis node become the new master.

RedisKeyRegistrationHandler is not smart enough and still tries to write to the old master node:

{"timestamp":"2025-03-04T01:49:52.685Z","level":"ERROR","thread":"lettuce-epollEventLoop-4-4","logger":"org.apache.james.events.RedisKeyRegistrationHandler","message":"Error while binding key","context":"default","exception":"io.lettuce.core.RedisReadOnlyException: READONLY You can't write against a read only replica.
	at io.lettuce.core.internal.ExceptionFactory.createExecutionException(ExceptionFactory.java:144)
	at io.lettuce.core.internal.ExceptionFactory.createExecutionException(ExceptionFactory.java:116)
	at io.lettuce.core.RedisPublisher$SubscriptionCommand.doOnComplete(RedisPublisher.java:761)
	at io.lettuce.core.protocol.CommandWrapper.complete(CommandWrapper.java:65)
	at io.lettuce.core.protocol.CommandWrapper.complete(CommandWrapper.java:63)
	at io.lettuce.core.protocol.CommandHandler.complete(CommandHandler.java:745)
	at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:680)
	at io.lettuce.core.protocol.CommandHandler.channelRead(CommandHandler.java:597)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1407)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:918)
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:799)
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501)
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:994)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Unknown Source)
"}

We need to try to make it smarter: following the Redis failover, it should write to the new master node.

[chibenwa]

Maybe that's your explanation...

#1586

[Arsnael]

Might be potentially I think more connected to the way we connect after we create the redis client.

We connect normally, like master/replica way, but actually in the client you have connectSentinel methods that should be I think better adapted for handling change of master in case of failover