"Needed to have 6 in buffer but only had 0"

In the HR test suite I had to disable a test, as seen here:

https://github.com/hibernate/hibernate-reactive/blob/2ff95a963d18c863853f6258490d4ace341eb00c/hibernate-reactive-core/src/test/java/org/hibernate/reactive/OrderedEmbeddableCollectionTest.java#L32

because of an intermittent error that only occurred on DB2 when running the whole test suite (and not the single test).

From the error message it looks like this is something y'all know about already.

ERROR errors [vert.x-eventloop-thread-0] failed to execute statement [select orderedemb0_.id as id1_0_0_, orderedemb0_.title as title2_0_0_ from EAuthor orderedemb0_ where orderedemb0_.id=?]
ERROR errors [vert.x-eventloop-thread-0] could not load an entity: [org.hibernate.reactive.OrderedEmbeddableCollectionTest$Author#1]
java.util.concurrent.CompletionException: java.lang.IllegalStateException: Needed to have 6 in buffer but only had 0. In JDBC we would normally block here but need to find a non-blocking solution
	at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:331) ~[?:?]
	at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:346) ~[?:?]
	at java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:632) ~[?:?]
	at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506) ~[?:?]
	at java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:2088) ~[?:?]
	at org.hibernate.reactive.pool.impl.Handlers.lambda$toCompletionStage$0(Handlers.java:29) ~[main/:?]
	at io.vertx.sqlclient.impl.SqlResultHandler.fail(SqlResultHandler.java:103) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.sqlclient.impl.SqlResultHandler.handle(SqlResultHandler.java:89) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.sqlclient.impl.SqlResultHandler.handle(SqlResultHandler.java:33) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.sqlclient.impl.TransactionImpl.lambda$null$3(TransactionImpl.java:181) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.sqlclient.impl.TransactionImpl.lambda$rollback$2(TransactionImpl.java:140) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.sqlclient.impl.SocketConnectionBase.handleMessage(SocketConnectionBase.java:241) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.sqlclient.impl.SocketConnectionBase.lambda$init$0(SocketConnectionBase.java:88) ~[vertx-sql-client-3.9.5.jar:3.9.5]
	at io.vertx.core.net.impl.NetSocketImpl.lambda$new$2(NetSocketImpl.java:101) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.streams.impl.InboundBuffer.handleEvent(InboundBuffer.java:237) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.streams.impl.InboundBuffer.write(InboundBuffer.java:127) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.net.impl.NetSocketImpl.handleMessage(NetSocketImpl.java:357) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.impl.ContextImpl.executeTask(ContextImpl.java:366) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.impl.EventLoopContext.execute(EventLoopContext.java:43) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.impl.ContextImpl.executeFromIO(ContextImpl.java:229) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.vertx.core.net.impl.VertxHandler.channelRead(VertxHandler.java:163) ~[vertx-core-3.9.5.jar:3.9.5]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.vertx.db2client.impl.codec.DB2Encoder.lambda$write$0(DB2Encoder.java:72) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.codec.DB2Decoder.decodePayload(DB2Decoder.java:97) [vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.codec.DB2Decoder.decode(DB2Decoder.java:53) [vertx-db2-client-3.9.5.jar:3.9.5]
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:501) [netty-codec-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:440) [netty-codec-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276) [netty-codec-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:714) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493) [netty-transport-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) [netty-common-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [netty-common-4.1.49.Final.jar:4.1.49.Final]
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [netty-common-4.1.49.Final.jar:4.1.49.Final]
	at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: java.lang.IllegalStateException: Needed to have 6 in buffer but only had 0. In JDBC we would normally block here but need to find a non-blocking solution
	at io.vertx.db2client.impl.drda.DRDAResponse.ensureALayerDataInBuffer(DRDAResponse.java:1462) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.drda.DRDAResponse.readDssHeader(DRDAResponse.java:878) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.drda.DRDAResponse.startSameIdChainParse(DRDAResponse.java:52) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.drda.DRDAQueryResponse.readDescribeInput(DRDAQueryResponse.java:81) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.drda.DRDAQueryResponse.readPrepareDescribeInputOutput(DRDAQueryResponse.java:53) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.codec.PrepareStatementCodec.decodePayload(PrepareStatementCodec.java:76) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	at io.vertx.db2client.impl.codec.DB2Decoder.decodePayload(DB2Decoder.java:80) ~[vertx-db2-client-3.9.5.jar:3.9.5]
	... 21 more

参照されている OrderedEmbeddableCollectionTest.java テストから始め、単独で実行した場合と、DB2 に対して Hibernate Reactive の完全なスイートを実行した場合を比較します。スタックトレースにある DRDAResponse.ensureALayerDataInBuffer()、readDssHeader()、PrepareStatementCodec.decodePayload() を通じて失敗を追跡します。断続的に発生するバッファエラーの原因を特定し、DB2 のテスト実行が失敗しないようにできれば完了です。