Spring Data Multiple Host Setting for MYSQL R2DBC

Question

I am trying to access the read replica database from Spring R2DBC.My connection string looks like this

spring:
  r2dbc:
    url: r2dbc:mysql://db-master-dev-pvt.xyz***.com:3306,db-replica-dev-pvt.xyz**.com:3306/employee?autoReconnect=true&useUnicode=yes&characterEncoding=UTF-8
    username: 
    password: 

but I am getting an unknown host. I am following the below document https://r2dbc.io/spec/0.8.2.RELEASE/spec/html/#overview.connection.discovery as per Documentation, we can multiple host configurations separated by comma (,) but when I have tried to do a query or do any health check it's throwing an unknown host exception. Same configuration working fine with Spring Data JPA.

 {
                "database": "MySQL",
                "validationQuery": "validate(REMOTE)",
                "error": "java.net.UnknownHostException: failed to resolve 'db-master-dev-pvt.xyz**.com:3306,db-replica-dev-pvt.xyz**.com:3306'"
            }  

Stack Trace

{"@timestamp":"2021-02-12T11:34:18.438Z","@version":"1","message":"Operator called default onErrorDropped","logger_name":"reactor.core.publisher.Operators","thread_name":"reactor-tcp-epoll-1","level":"ERROR","level_value":40000,"stack_trace":"java.net.UnknownHostException: failed to resolve 'myDB-master-dev-pvt.xyz**.com:3306,myDB-replica-dev-pvt.myAPI.com:3306' after 2 queries \n\tat io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:1013)\n\t... 35 common frames omitted\nWrapped by: org.springframework.transaction.CannotCreateTransactionException: Could not open R2DBC Connection for transaction; nested exception is java.net.UnknownHostException: failed to resolve 'myDB-master-dev-pvt.myAPI.com:3306,MyDB-replica-dev-pvt.myAPI.com:3306' after 2 queries \n\tat org.springframework.r2dbc.connection.R2dbcTransactionManager.lambda$null$5(R2dbcTransactionManager.java:226)\n\tat reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onError(FluxOnErrorResume.java:94)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.MonoFlatMap$FlatMapMain.onError(MonoFlatMap.java:172)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.FluxPeek$PeekSubscriber.onError(FluxPeek.java:221)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.FluxRetry$RetrySubscriber.onError(FluxRetry.java:94)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.FluxPeekFuseable$PeekFuseableSubscriber.onError(FluxPeekFuseable.java:234)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.MonoFlatMap$FlatMapMain.onError(MonoFlatMap.java:172)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.FluxPeek$PeekSubscriber.onError(FluxPeek.java:221)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.FluxPeek$PeekSubscriber.onError(FluxPeek.java:221)\n\tat reactor.pool.AbstractPool$Borrower.fail(AbstractPool.java:427)\n\tat reactor.pool.SimpleDequePool.lambda$drainLoop$5(SimpleDequePool.java:309)\n\tat reactor.core.publisher.FluxDoOnEach$DoOnEachSubscriber.onError(FluxDoOnEach.java:186)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.MonoFlatMap$FlatMapMain.onError(MonoFlatMap.java:172)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.MonoFlatMap$FlatMapMain.onError(MonoFlatMap.java:172)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.FluxMap$MapSubscriber.onError(FluxMap.java:132)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.MonoCreate$DefaultMonoSink.error(MonoCreate.java:189)\n\tat reactor.netty.resources.NewConnectionProvider$DisposableConnect.onError(NewConnectionProvider.java:139)\n\tat org.springframework.cloud.sleuth.instrument.reactor.ScopePassingSpanSubscriber.onError(ScopePassingSpanSubscriber.java:95)\n\tat reactor.core.publisher.MonoFlatMap$FlatMapMain.secondError(MonoFlatMap.java:192)\n\tat reactor.core.publisher.MonoFlatMap$FlatMapInner.onError(MonoFlatMap.java:259)\n\tat reactor.netty.transport.TransportConnector$MonoChannelPromise.tryFailure(TransportConnector.java:464)\n\tat reactor.netty.transport.TransportConnector.lambda$doResolveAndConnect$6(TransportConnector.java:271)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:578)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:552)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:491)\n\tat io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:616)\n\tat io.netty.util.concurrent.DefaultPromise.setFailure0(DefaultPromise.java:609)\n\tat io.netty.util.concurrent.DefaultPromise.setFailure(DefaultPromise.java:109)\n\tat io.netty.resolver.InetSocketAddressResolver$1.operationComplete(InetSocketAddressResolver.java:62)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:578)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:571)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:550)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:491)\n\tat io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:616)\n\tat io.netty.util.concurrent.DefaultPromise.setFailure0(DefaultPromise.java:609)\n\tat io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:117)\n\tat io.netty.resolver.dns.DnsNameResolver.tryFailure(DnsNameResolver.java:936)\n\tat io.netty.resolver.dns.DnsNameResolver.access$500(DnsNameResolver.java:90)\n\tat io.netty.resolver.dns.DnsNameResolver$5.operationComplete(DnsNameResolver.java:956)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:578)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:552)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:491)\n\tat io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:616)\n\tat io.netty.util.concurrent.DefaultPromise.setFailure0(DefaultPromise.java:609)\n\tat io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:117)\n\tat io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:1021)\n\tat io.netty.resolver.dns.DnsResolveContext.tryToFinishResolve(DnsResolveContext.java:966)\n\tat io.netty.resolver.dns.DnsResolveContext.query(DnsResolveContext.java:414)\n\tat io.netty.resolver.dns.DnsResolveContext.tryToFinishResolve(DnsResolveContext.java:938)\n\tat io.netty.resolver.dns.DnsResolveContext.access$700(DnsResolveContext.java:63)\n\tat io.netty.resolver.dns.DnsResolveContext$2.operationComplete(DnsResolveContext.java:467)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:578)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:571)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:550)\n\tat io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:491)\n\tat io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:616)\n\tat io.netty.util.concurrent.DefaultPromise.setSuccess0(DefaultPromise.java:605)\n\tat io.netty.util.concurrent.DefaultPromise.trySuccess(DefaultPromise.java:104)\n\tat io.netty.resolver.dns.DnsQueryContext.trySuccess(DnsQueryContext.java:201)\n\tat io.netty.resolver.dns.DnsQueryContext.finish(DnsQueryContext.java:193)\n\tat io.netty.resolver.dns.DnsNameResolver$DnsResponseHandler.channelRead(DnsNameResolver.java:1230)\n\tat io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)\n\tat io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)\n\tat io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)\n\tat io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)\n\tat io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)\n\tat io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)\n\tat io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)\n\tat io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)\n\tat io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)\n\tat io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)\n\tat io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)\n\tat io.netty.channel.epoll.EpollDatagramChannel.read(EpollDatagramChannel.java:681)\n\tat io.netty.channel.epoll.EpollDatagramChannel.access$100(EpollDatagramChannel.java:58)\n\tat io.netty.channel.epoll.EpollDatagramChannel$EpollDatagramChannelUnsafe.epollInReady(EpollDatagramChannel.java:499)\n\tat io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:480)\n\tat io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378)\n\tat io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)\n\tat io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)\n\tat io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)\n\tat java.lang.Thread.run(Thread.java:748)\nWrapped by: reactor.core.Exceptions$ErrorCallbackNotImplemented: org.springframework.transaction.CannotCreateTransactionException: Could not open R2DBC Connection for transaction; nested exception is java.net.UnknownHostException: failed to resolve 'myDB-master-dev-pvt.xyz**.com:3306,myDB-replica-dev-pvt.xyz**.com:3306' after 2 queries \n","caller_class_name":"reactor.util.Loggers$Slf4JLogger","caller_method_name":"error","caller_file_name":"Loggers.java","caller_line_number":314,"traceId":"","instance_activeProfiles":"dev","instance_port":"8080","instance_ip":"instance_ip_IS_UNDEFINED","instance_application_name":"employee-adjustment-service"}

Thanks

Answer 1

I have done the analysis, I am providing that here so that in future if any one want to check on mysql they must see this before planing to R2DBC. I went to the R2DBC team and after that, I found that driver which I am using that don't have multi-host. and Officaily they support on postgres and MSSQL and H2,

I am using below driver

<!-- https://mvnrepository.com/artifact/dev.miku/r2dbc-mysql -->
<dependency>
    <groupId>dev.miku</groupId>
    <artifactId>r2dbc-mysql</artifactId>
    <version>0.8.2.RELEASE</version>
</dependency>

so this need to be fixed in this driver I have to open an issue there https://github.com/mirromutth/r2dbc-mysql/issues/169 in order to fix it. Thanks, Mark @mp911de from Spring R2DBC for clarification and support.

Answer 2

I`m able to invoke with multiple hosts comma seperated hosts

r2dbc.oracle.config.host1=a.b.com
r2dbc.oracle.config.host2=x.y.com

And My config class goes as below

@Value("${r2dbc.oracle.config.host1}")
    private String host1;

    @Value("${r2dbc.oracle.config.host2}")
    private String host2;

@Bean()
    @Qualifier("remoteabcConnectionFactory")
    public ConnectionFactory remoteRemedyConnectionFactory() {
        String hosts = host1 + "," + host2;
        return ConnectionFactories.get(ConnectionFactoryOptions.builder()
                .option(DRIVER, driver)
                .option(HOST, host)
                .option(HOST, hosts)
                .option(PORT, Integer.valueOf(port))
                .option(USER, user)
                .option(PASSWORD, password)
                .option(DATABASE, database)
                .build());
    }

You can also get comma separated hosts from one propertt param in app.properties