Lettuce doesn't handle deleted stream items (NullPointerException)

[chemist777]

Bug Report

When I try to read pending messages via XREADGROUP I get the following NullPointerException.

It occurs when a pending message is already deleted from the stream due to its size limit.

The issue is related to the Redis behavior described in this comment https://github.com/redis/redis/blob/5.0.2/src/t_stream.c#L1031.

Also, Python client faced the same issue the previous year redis/redis-py#1116

Current Behavior

Stack trace

java.lang.NullPointerException: null
	at io.lettuce.core.codec.ByteArrayCodec.getBytes(ByteArrayCodec.java:84)
	at io.lettuce.core.codec.ByteArrayCodec.decodeKey(ByteArrayCodec.java:59)
	at io.lettuce.core.codec.ByteArrayCodec.decodeKey(ByteArrayCodec.java:28)
	at io.lettuce.core.output.StreamReadOutput.set(StreamReadOutput.java:73)
	at io.lettuce.core.protocol.RedisStateMachine.safeSet(RedisStateMachine.java:810)
	at io.lettuce.core.protocol.RedisStateMachine.handleNull(RedisStateMachine.java:392)
	at io.lettuce.core.protocol.RedisStateMachine$State$Type.handle(RedisStateMachine.java:206)
	at io.lettuce.core.protocol.RedisStateMachine.doDecode(RedisStateMachine.java:334)
	at io.lettuce.core.protocol.RedisStateMachine.decode(RedisStateMachine.java:295)
	at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:799)
	at io.lettuce.core.protocol.CommandHandler.decode0(CommandHandler.java:750)
	at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:733)
	at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:618)
	at io.lettuce.core.protocol.CommandHandler.channelRead(CommandHandler.java:560)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:714)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
	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(Thread.java:834)

Expected behavior/code

No NPE.

Environment

• Lettuce version(s): 6.0.0.RELEASE
• Redis version: 6.0.8

Also, I use ByteArrayCodec for keys & values.

[mp911de]

Thanks a lot for letting us know. That's fixed and backported now.