NodeTopologyView passes null-Value to StringReader constructor

[m-ibot]

Bug Report

I ran into this issue after a Spring Boot update from Spring Boot 2.4.x to 2.6.3. This bug appears with lettuce-core 6.1.6.RELEASE. After downgrading it manually to 6.1.5.RELEASE, the error did not show up anymore.

Based on the git history, this bug might be a result of #1923

Unfortunately I could not figure out the root cause of this error. It appeared only on one environment and I could not reproduce it anywhere else. All I can provide is the stack trace and what I could figure out by reading the code.

Anyway, I hope this information helps:

Current Behavior

We have a scheduled task that writes data to Redis. Whenever this tasks runs the NullPointerException is thrown.

Stack trace

java.lang.NullPointerException: null
	at java.base/java.io.StringReader.<init>(StringReader.java:50)
	at io.lettuce.core.cluster.topology.NodeTopologyView.parseInfo(NodeTopologyView.java:116)
	at io.lettuce.core.cluster.topology.NodeTopologyView.<init>(NodeTopologyView.java:67)
	at io.lettuce.core.cluster.topology.NodeTopologyView.from(NodeTopologyView.java:90)
	at io.lettuce.core.cluster.topology.DefaultClusterTopologyRefresh.getNodeSpecificViews(DefaultClusterTopologyRefresh.java:232)
	at io.lettuce.core.cluster.topology.DefaultClusterTopologyRefresh.lambda$null$4(DefaultClusterTopologyRefresh.java:110)
	at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1072)
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
	at java.base/java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:2088)
	at io.lettuce.core.protocol.AsyncCommand.doCompleteExceptionally(AsyncCommand.java:139)
	at io.lettuce.core.protocol.AsyncCommand.completeResult(AsyncCommand.java:120)
	at io.lettuce.core.protocol.AsyncCommand.complete(AsyncCommand.java:111)
	at io.lettuce.core.cluster.topology.TimedAsyncCommand.complete(TimedAsyncCommand.java:52)
	at io.lettuce.core.protocol.CommandWrapper.complete(CommandWrapper.java:63)
	at io.lettuce.core.protocol.CommandHandler.complete(CommandHandler.java:746)
	at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:681)
	at io.lettuce.core.protocol.CommandHandler.channelRead(CommandHandler.java:598)
	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.handler.ssl.SslHandler.unwrap(SslHandler.java:1372)
	at io.netty.handler.ssl.SslHandler.decodeJdkCompatible(SslHandler.java:1235)
	at io.netty.handler.ssl.SslHandler.decode(SslHandler.java:1284)
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:510)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:449)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:279)
	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:722)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:658)
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:584)
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:496)
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986)
	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:829)

StringReader.java is a JDK class that will throw a NullPointerException if a null value is passed as parameter, because it calls .length() on it.

This value is passed in NodeTopologyView#parseInfo

    private static Properties parseInfo(String info) {
        Properties properties = new Properties();
        try {
            properties.load(new StringReader(info));
        } catch (IOException e) {
            // wtf?
        }
        return properties;
    }

It would be interesting to know where the null-value for info comes from. the only point that I could see is the method NodeTopologyView#optionallyGet that must have been called in Line NodeTopologyView.java:90 (see Stacktrace). This method might return null:

    private static <T> T optionallyGet(TimedAsyncCommand<?, ?, T> command) {
        if (command.isCompletedExceptionally()) {
            return null;
        }
        return command.join();
    }

Since this seems to happen if the TimedAsyncCommand was completed exceptionally, this NullPointerException seems to be a follow up error. Anyway if a null value is used it should be ensured that it does not lead to a NullPointerException.

Expected behavior/code

No NullPointerException is thrown.

Environment

• Lettuce version(s): 6.1.6.RELEASE

Possible Solution

null values are handled in a way that they don't lead to a NullPointerException.

In the best case some information why TimedAsyncCommand is completed exceptionally in optionallyGet is provided (e.g. by provide some logging) so that it is possible to see what exception it was and react on it as user of lettuce-core.

[mp911de]

That's fixed now.

[m-ibot]

Thank you for the fix!