When running Blockhound on my project it detects this UUID generation as a blocking call. I am thinking that it should be updated and maybe you can set the creation of this class on a separate thread pool or fix the issue with generating the id of the TransactionContext.
https://github.com/spring-projects/spring-framework/blob/360f555e77bcb46d740151db447ffba0c6a09b51/spring-tx/src/main/java/org/springframework/transaction/reactive/TransactionContext.java#L43
This is the stack trace from Blockhound
reactor.blockhound.BlockingOperationError: Blocking call! java.io.FileInputStream#readBytes
at java.base/java.io.FileInputStream.readBytes(FileInputStream.java)
at java.base/java.io.FileInputStream.read(FileInputStream.java:273)
at java.base/java.io.FilterInputStream.read(FilterInputStream.java:133)
at java.base/sun.security.provider.NativePRNG$RandomIO.readFully(NativePRNG.java:424)
at java.base/sun.security.provider.NativePRNG$RandomIO.ensureBufferValid(NativePRNG.java:526)
at java.base/sun.security.provider.NativePRNG$RandomIO.implNextBytes(NativePRNG.java:545)
at java.base/sun.security.provider.NativePRNG$NonBlocking.engineNextBytes(NativePRNG.java:318)
at java.base/java.security.SecureRandom.nextBytes(SecureRandom.java:741)
at java.base/java.util.UUID.randomUUID(UUID.java:150)
at org.springframework.transaction.reactive.TransactionContext.<init>(TransactionContext.java:43)
at org.springframework.transaction.reactive.TransactionContext.<init>(TransactionContext.java:60)
at org.springframework.transaction.reactive.TransactionContextHolder.createContext(TransactionContextHolder.java:63)
at org.springframework.transaction.reactive.TransactionContextManager.lambda$getOrCreateContext$2(TransactionContextManager.java:91)
at reactor.core.publisher.MonoContextWrite.subscribeOrReturn(MonoContextWrite.java:38)
at reactor.core.publisher.Mono.subscribe(Mono.java:4135)
at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onError(FluxOnErrorResume.java:103)
at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onError(FluxContextWrite.java:121)
at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onError(FluxContextWrite.java:121)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.secondError(MonoFlatMap.java:192)
at reactor.core.publisher.MonoFlatMap$FlatMapInner.onError(MonoFlatMap.java:259)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.secondError(MonoFlatMap.java:192)
at reactor.core.publisher.MonoFlatMap$FlatMapInner.onError(MonoFlatMap.java:259)
at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onError(FluxOnErrorResume.java:106)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onError(ReactorContextTestExecutionListener.java:125)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onError(MonoIgnoreThen.java:270)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:227)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.secondComplete(MonoFlatMap.java:196)
at reactor.core.publisher.MonoFlatMap$FlatMapInner.onComplete(MonoFlatMap.java:268)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.secondComplete(MonoFlatMap.java:196)
at reactor.core.publisher.MonoFlatMap$FlatMapInner.onComplete(MonoFlatMap.java:268)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:259)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.pool.SimpleDequePool$QueuePoolRecyclerInner.onComplete(SimpleDequePool.java:690)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.Operators.complete(Operators.java:136)
at reactor.core.publisher.MonoEmpty.subscribe(MonoEmpty.java:45)
at reactor.core.publisher.Mono.subscribe(Mono.java:4150)
at reactor.pool.SimpleDequePool$QueuePoolRecyclerMono.subscribe(SimpleDequePool.java:802)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:236)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:259)
at reactor.core.publisher.Operators.complete(Operators.java:136)
at reactor.core.publisher.MonoEmpty.subscribe(MonoEmpty.java:45)
at reactor.core.publisher.Mono.subscribe(Mono.java:4150)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:255)
at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51)
at org.springframework.cloud.sleuth.instrument.reactor.SleuthMonoLift.subscribe(ReactorHooksHelper.java:225)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:236)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.MonoIgnoreElements$IgnoreElementsSubscriber.onComplete(MonoIgnoreElements.java:88)
at reactor.core.publisher.FluxHandleFuseable$HandleFuseableSubscriber.onNext(FluxHandleFuseable.java:201)
at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1815)
at reactor.core.publisher.MonoSupplier.subscribe(MonoSupplier.java:61)
at reactor.core.publisher.Mono.subscribe(Mono.java:4150)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:255)
at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51)
at org.springframework.cloud.sleuth.instrument.reactor.SleuthMonoLift.subscribe(ReactorHooksHelper.java:225)
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157)
at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:120)
at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2397)
at reactor.core.publisher.FluxMap$MapSubscriber.request(FluxMap.java:162)
at reactor.core.publisher.MonoFlatMap$FlatMapMain.onSubscribe(MonoFlatMap.java:110)
at reactor.core.publisher.FluxMap$MapSubscriber.onSubscribe(FluxMap.java:92)
at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:54)
at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55)
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:236)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.core.publisher.MonoIgnoreElements$IgnoreElementsSubscriber.onComplete(MonoIgnoreElements.java:88)
at io.r2dbc.postgresql.util.FluxDiscardOnCancel$FluxDiscardOnCancelSubscriber.onComplete(FluxDiscardOnCancel.java:99)
at reactor.core.publisher.Operators.complete(Operators.java:136)
at reactor.core.publisher.FluxEmpty.subscribe(FluxEmpty.java:41)
at reactor.core.publisher.FluxDefer.subscribe(FluxDefer.java:54)
at io.r2dbc.postgresql.util.FluxDiscardOnCancel.subscribe(FluxDiscardOnCancel.java:49)
at reactor.core.publisher.MonoFromFluxOperator.subscribe(MonoFromFluxOperator.java:81)
at org.springframework.cloud.sleuth.instrument.reactor.SleuthMonoLift.subscribe(ReactorHooksHelper.java:225)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:236)
at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51)
at org.springframework.cloud.sleuth.instrument.reactor.SleuthMonoLift.subscribe(ReactorHooksHelper.java:225)
at reactor.core.publisher.Mono.subscribe(Mono.java:4150)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:255)
at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51)
at org.springframework.cloud.sleuth.instrument.reactor.SleuthMonoLift.subscribe(ReactorHooksHelper.java:225)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:236)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.core.publisher.MonoIgnoreElements$IgnoreElementsSubscriber.onComplete(MonoIgnoreElements.java:88)
at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onComplete(FluxContextWrite.java:126)
at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:366)
at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onComplete(FluxConcatMap.java:275)
at reactor.core.publisher.Operators.complete(Operators.java:136)
at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:147)
at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:86)
at reactor.core.publisher.MonoFromFluxOperator.subscribe(MonoFromFluxOperator.java:81)
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:236)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203)
at org.springframework.security.test.context.support.ReactorContextTestExecutionListener$DelegateTestExecutionListener$SecuritySubContext.onComplete(ReactorContextTestExecutionListener.java:130)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:209)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:2057)
at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:259)
at reactor.core.publisher.MonoIgnoreElements$IgnoreElementsSubscriber.onComplete(MonoIgnoreElements.java:88)
at io.r2dbc.postgresql.util.FluxDiscardOnCancel$FluxDiscardOnCancelSubscriber.onComplete(FluxDiscardOnCancel.java:99)
at io.r2dbc.postgresql.util.FluxDiscardOnCancel$FluxDiscardOnCancelSubscriber.onComplete(FluxDiscardOnCancel.java:99)
at reactor.core.publisher.FluxHandle$HandleSubscriber.onComplete(FluxHandle.java:212)
at reactor.core.publisher.FluxCreate$BaseSink.complete(FluxCreate.java:439)
at reactor.core.publisher.FluxCreate$BufferAsyncSink.drain(FluxCreate.java:784)
at reactor.core.publisher.FluxCreate$BufferAsyncSink.complete(FluxCreate.java:732)
at reactor.core.publisher.FluxCreate$SerializedFluxSink.drainLoop(FluxCreate.java:240)
at reactor.core.publisher.FluxCreate$SerializedFluxSink.drain(FluxCreate.java:206)
at reactor.core.publisher.FluxCreate$SerializedFluxSink.complete(FluxCreate.java:197)
at io.r2dbc.postgresql.client.ReactorNettyClient$Conversation.complete(ReactorNettyClient.java:719)
at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.emit(ReactorNettyClient.java:984)
at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.onNext(ReactorNettyClient.java:860)
at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.onNext(ReactorNettyClient.java:767)
at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:118)
at reactor.core.publisher.FluxPeekFuseable$PeekConditionalSubscriber.onNext(FluxPeekFuseable.java:854)
at reactor.core.publisher.FluxMap$MapConditionalSubscriber.onNext(FluxMap.java:220)
at reactor.core.publisher.FluxMap$MapConditionalSubscriber.onNext(FluxMap.java:220)
at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:280)
at reactor.netty.channel.FluxReceive.onInboundNext(FluxReceive.java:389)
at reactor.netty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:401)
at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:94)
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.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296)
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:719)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
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:830)
Comment From: jhoeller
Since we're only using that UUID for logging purposes, even just synchronization trace logging that we could get rid of completely (with standard as well as reactive transactions), I'm inclined to make UUID generation lazy there - and to deprecate its accessors.
@mp911de what's your take on this? Are you aware of any use of the context id (or the name including the context id) outside of the core transaction module?
Comment From: mp911de
I'm not aware of any outside usage, even Spring Data R2DBC doesn't use the context. In retrospect, using a UUID seems to be not an ideal choice because of the blocking access to the random source. Let's revisit this arrangement for the next major release.
Comment From: jhoeller
Alright, I'll proceed with the steps above then. Let's revisit the transaction identification problem in Spring Framework 6 indeed, and simply keep the current mechanism in deprecated form for the time being. Most importantly, by lazily creating the UUID, we'll avoid the overhead (and the potential blocking) for every created transaction. With the trace log statements removed, this effectively means that we'll never trigger that UUID to begin with, unless some custom code calls getContextId()/getName(). That should deliver significant benefit in 5.3.9 already and not constrain use for 6 either.