possible reason for NoSuchElementException

[spiritlcx]

Hi,

We got this exception when using lettuce. Is there any possible reason for the exception? If you need more information, please let me know. Thanks very much.

java.util.NoSuchElementException: Source was empty
at reactor.core.publisher.MonoSingle$SingleSubscriber.onComplete(MonoSingle.java:174) ~[reactor-core-3.4.33.jar!/:3.4.33]
at io.lettuce.core.RedisPublisher$ImmediateSubscriber.onComplete(RedisPublisher.java:896) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.RedisPublisher$State.onAllDataRead(RedisPublisher.java:698) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.RedisPublisher$State$3.read(RedisPublisher.java:608) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.RedisPublisher$State$3.onDataAvailable(RedisPublisher.java:565) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.RedisPublisher$RedisSubscription.onDataAvailable(RedisPublisher.java:326) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.RedisPublisher$RedisSubscription.onAllDataRead(RedisPublisher.java:341) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.RedisPublisher$SubscriptionCommand.doOnComplete(RedisPublisher.java:778) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.protocol.CommandWrapper.complete(CommandWrapper.java:65) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.protocol.CommandWrapper.complete(CommandWrapper.java:63) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.cluster.ClusterCommand.complete(ClusterCommand.java:65) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.protocol.CommandWrapper.complete(CommandWrapper.java:63) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.protocol.CommandHandler.complete(CommandHandler.java:747) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.protocol.CommandHandler.decode(CommandHandler.java:682) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.lettuce.core.protocol.CommandHandler.channelRead(CommandHandler.java:599) ~[lettuce-core-6.1.10.RELEASE.jar!/:6.1.10.RELEASE]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:800) ~[netty-transport-classes-epoll-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:509) ~[netty-transport-classes-epoll-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:407) ~[netty-transport-classes-epoll-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.100.Final.jar!/:4.1.100.Final]
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.100.Final.jar!/:4.1.100.Final]
at java.lang.Thread.run(Thread.java:891) ~[?:?]

Best Regards,
Chenxi li

[mp911de]

Looks like you're using some publisher to expect a Mono.single().

[spiritlcx]

Hi,

We use it in this way. Could you have a look at it.

Thanks very much.

    private final static String RATE_LIMIT_SCRIPT = "local limitCount = redis.call('incr',KEYS[1]); local t = redis.call('ttl',KEYS[1]); if (limitCount == 1 or t == -1) then  redis.call(\"expire\",KEYS[1],ARGV[2]) end; if limitCount > tonumber(ARGV[1]) then  return false end; return true";
    private final String rateLimitKey;
    private final RedisScriptingReactiveCommands<String, String> commands;
    private final String[] rateLimitArg;
    private final AtomicReference<String> RATE_LIMIT_SCRIPT_SHA = new AtomicReference<>();

    public Mono<Boolean> rateLimit(String key) {
        return scriptSha1()
                .flatMap(sha1 -> evalsha(sha1, new String[]{rateLimitKey + key}, rateLimitArg)
                        .single()
                        .onErrorResume(RedisNoScriptException.class, e -> {
                            log.warn("rateLimit error", e);
                            // After encountering a RedisNoScriptException, reload the Lua script and return true for this call without affecting the business invocation.
                            RATE_LIMIT_SCRIPT_SHA.compareAndSet(sha1, null);
                            return Mono.just(true);
                        })
                );

    }

    private Mono<String> scriptSha1() {
        return Mono.justOrEmpty(RATE_LIMIT_SCRIPT_SHA.get())
                .switchIfEmpty(commands.scriptLoad(RATE_LIMIT_SCRIPT)
                        .map(newSha1 -> {
                            String oldSha1 = this.RATE_LIMIT_SCRIPT_SHA.compareAndExchange(null, newSha1);
                            if (oldSha1 == null) {
                                return newSha1;
                            } else {
                                return oldSha1;
                            }
                        }));
    }

    private Flux<Boolean> evalsha(String sha1, String[] key, String[] args) {
        return commands.evalsha(sha1, ScriptOutputType.BOOLEAN, key, args);
    }

[tishun]

@spiritlcx this seems like a very specific question to a relatively complicated piece of code.

I think this question is better suited for the Stackoverflow or some similar forum.

If you have specific questions about how to use the Lettuce driver please clarify your question.