NullPointerException from MasterSlaveTopologyRefresh.java

[kas-kad]

Bug Report

Current Behavior

We had a successful Redis failover but the application didn't manage to handle it properly. Current setup is: 9 Sentinels, 1 Master, 3 Slaves.

First we had dozens of Timeout exceptions, that's ok:

io.lettuce.core.RedisCommandTimeoutException: Command timed out

Later on we get couple of these, which I don't think is ok:

java.lang.NullPointerException: null
	at io.lettuce.core.masterslave.MasterSlaveTopologyRefresh.getNodeSpecificViews(MasterSlaveTopologyRefresh.java:111)
	at io.lettuce.core.masterslave.MasterSlaveTopologyRefresh.getNodes(MasterSlaveTopologyRefresh.java:77)
	at io.lettuce.core.masterslave.MasterSlave.lambda$connectSentinel$0(MasterSlave.java:174)
	at java.util.concurrent.CopyOnWriteArrayList.forEach(CopyOnWriteArrayList.java:891)
	at io.lettuce.core.masterslave.SentinelTopologyRefresh.lambda$null$2(SentinelTopologyRefresh.java:149)
	at io.netty.util.concurrent.PromiseTask$RunnableAdapter.call(PromiseTask.java:38)
	at io.netty.util.concurrent.ScheduledFutureTask.run(ScheduledFutureTask.java:125)
	at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:66)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.lang.Thread.run(Thread.java:748)

After that we end up with infinite:

io.lettuce.core.RedisCommandExecutionException: READONLY You can't write against a read only replica.

Input Code

    private val redisUri: RedisURI by lazy {
        val redisUriBuilder = RedisURI.builder()
        sentinels
            .split(",")
            .forEach {
                val (host, port) = it.split(":")
                redisUriBuilder
                    .withSentinel(host, port.toInt())
                    .withSentinelMasterId(master)
                    .withDatabase(2)
                    .withTimeout(Duration.ofMillis(defaultTimeoutMillis))
            }
        redisUriBuilder.build()
    }

    private val connection: StatefulRedisMasterSlaveConnection<String, String> by lazy {
        val connection = MasterSlave
            .connect(client, Utf8StringCodec(), redisUri)
        connection.readFrom = ReadFrom.MASTER
        connection
    }

    private val client: RedisClient = RedisClient.create()

Expected behavior/code

The successful failover must not cause the application stop functioning.

Environment

• Lettuce version(s): 5.0.1.RELEASE
• Redis version: 5.0.3

[mp911de]

Thanks for reporting this bug.

[mp911de]

This issue was solved with #643 and Lettuce 5.1. Please upgrade to the latest version and retest.