R2DBC with Postgres: Unable to handle many connections and warning when inserting data

Task List

• Steps to reproduce provided
• Stacktrace (if present) provided
• Example that reproduces the problem uploaded to Github
• Full description of the issue provided (see below)

Steps to Reproduce

Follow the steps below (the code is based on the doc-examples/r2dbc-example-java but without the use of RxJava)

Download the project example at: https://github.com/ericsouza/micronaut-rest

Start a Postgres Database:

docker run --ulimit memlock=-1:-1 -it --rm=true --memory-swappiness=0 \
           --name micronaut-db -e POSTGRES_USER=micronaut \
           -e POSTGRES_PASSWORD=micronaut -e POSTGRES_DB=micronaut \
           -p 5432:5432 postgres:11.2

Run the project

./mvnw mn:run

Insert some fruits to database

curl -X POST -H "Content-Type: application/json" -d '{"name":"orange"}' http://localhost:8080/fruit && curl -X POST -H "Content-Type: application/json" -d '{"name":"grape"}' http://localhost:8080/fruit && curl -X POST -H "Content-Type: application/json" -d '{"name":"apple"}' http://localhost:8080/fruit

See the error:

13:54:43.016 [reactor-tcp-epoll-3] WARN  reactor.core.publisher.FluxUsingWhen - Async resource cleanup failed after cancel
io.r2dbc.postgresql.client.ReactorNettyClient$PostgresConnectionClosedException: Connection closed
	at io.r2dbc.postgresql.client.ReactorNettyClient.lambda$static$1(ReactorNettyClient.java:102)
	at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.close(ReactorNettyClient.java:1018)
	at io.r2dbc.postgresql.client.ReactorNettyClient.drainError(ReactorNettyClient.java:518)
	at io.r2dbc.postgresql.client.ReactorNettyClient.lambda$close$8(ReactorNettyClient.java:191)
	at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:44)
	at reactor.core.publisher.Mono.subscribe(Mono.java:3987)
	at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:173)
	at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:56)
	at reactor.core.publisher.FluxFromMonoOperator.subscribe(FluxFromMonoOperator.java:83)
	at reactor.core.publisher.FluxUsingWhen$UsingWhenSubscriber.cancel(FluxUsingWhen.java:342)
	at reactor.core.publisher.FluxUsingWhen$ResourceSubscriber.cancel(FluxUsingWhen.java:253)
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:81)
	at reactor.core.publisher.FluxUsingWhen$UsingWhenSubscriber.onNext(FluxUsingWhen.java:358)
	at reactor.core.publisher.FluxUsingWhen$UsingWhenSubscriber.onNext(FluxUsingWhen.java:358)
	at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onNext(FluxContextWrite.java:107)
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82)
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:127)
	at reactor.core.publisher.FluxFilterFuseable$FilterFuseableSubscriber.onNext(FluxFilterFuseable.java:118)
	at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1784)
	at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:127)
	at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2346)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:169)
	at reactor.core.publisher.MonoFlatMap$FlatMapInner.onSubscribe(MonoFlatMap.java:238)
	at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:96)
	at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:54)
	at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64)
	at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157)
	at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1784)
	at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249)
	at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1784)
	at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249)
	at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82)
	at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:118)
	at reactor.core.publisher.MonoFlatMapMany$FlatMapManyInner.onNext(MonoFlatMapMany.java:250)
	at reactor.core.publisher.FluxHandleFuseable$HandleFuseableSubscriber.onNext(FluxHandleFuseable.java:184)
	at reactor.core.publisher.FluxFilterFuseable$FilterFuseableConditionalSubscriber.onNext(FluxFilterFuseable.java:337)
	at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onNext(FluxContextWrite.java:107)
	at reactor.core.publisher.FluxPeekFuseable$PeekConditionalSubscriber.onNext(FluxPeekFuseable.java:854)
	at io.r2dbc.postgresql.util.FluxDiscardOnCancel$FluxDiscardOnCancelSubscriber.onNext(FluxDiscardOnCancel.java:86)
	at reactor.core.publisher.FluxCreate$BufferAsyncSink.drain(FluxCreate.java:793)
	at reactor.core.publisher.FluxCreate$BufferAsyncSink.next(FluxCreate.java:718)
	at reactor.core.publisher.FluxCreate$SerializedFluxSink.next(FluxCreate.java:154)
	at io.r2dbc.postgresql.client.ReactorNettyClient$Conversation.emit(ReactorNettyClient.java:735)
	at io.r2dbc.postgresql.client.ReactorNettyClient$BackendMessageSubscriber.emit(ReactorNettyClient.java:986)
	at io.r2dbc.postgresql.client.ReactorNettyClient$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$MapConditionalSubscriber.onNext(FluxMap.java:220)
	at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:267)
	at reactor.netty.channel.FluxReceive.onInboundNext(FluxReceive.java:377)
	at reactor.netty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:381)
	at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:94)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:311)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:432)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
	at io.netty.channel.DefaultChannelPipeline$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.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:795)
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:480)
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378)
	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:829)

Run basic load test:

wrk -t12 -c400 -d30s --latency http://localhost:8080/fruit

See the error:

13:51:10.625 [reactor-tcp-epoll-6] WARN i.r.p.client.ReactorNettyClient - Error: SEVERITY_LOCALIZED=FATAL, SEVERITY_NON_LOCALIZED=FATAL, CODE=53300, MESSAGE=sorry, too many clients already, FILE=proc.c, LINE=346, ROUTINE=InitProcess

Info

I’m evaluating the use of a new Java framework with fully reactive functionality. I’m basically choosing between Quarkus or Micronaut. In Quarkus I was able to run the load test above withou any problem, but some things in micronaut are really awesome to have.

Expected Behaviour

Run without errors and be able to handle the load test

Actual Behaviour

Receiveing Warning when inserting a fruit object to the dabase and also getting a lot of errors when using many connections.

Environment Information

• Operating System: pop-os 20.04
• Micronaut Version: 2.5.6
• JDK Version: adoptopenjdk-11

Example Application

• TODO: https://github.com/ericsouza/micronaut-rest

Am I doing something wrong? I almost sure that I am missing something

[dstepanov]

Put them in under options like driver

[cemo]

https://github.com/r2dbc/r2dbc-pool I think the properties are listed. Correct me if I am wrong.