I found a problem that with Spring Cloud Stream and Sleuth, grpc-client-spring-boot-starter is not reporting spans to Kafka.
In fact, it causes a number of beans being instantiated early. See following log printed by BeanPostProcessorChecker:
2017-10-01 20:20:58.745 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.kafka.annotation.KafkaBootstrapConfiguration' of type [org.springframework.kafka.annotation.KafkaBootstrapConfiguration$$EnhancerBySpringCGLIB$$a60515ef] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:58.789 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.instrument.async.AsyncDefaultAutoConfiguration$DefaultAsyncConfigurerSupport' of type [org.springframework.cloud.sleuth.instrument.async.AsyncDefaultAutoConfiguration$DefaultAsyncConfigurerSupport$$EnhancerBySpringCGLIB$$f94a22f] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:58.948 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.annotation.SleuthAnnotationAutoConfiguration' of type [org.springframework.cloud.sleuth.annotation.SleuthAnnotationAutoConfiguration$$EnhancerBySpringCGLIB$$d4b84a9e] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.365 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'sleuthAdvisorConfig' of type [org.springframework.cloud.sleuth.annotation.SleuthAdvisorConfig] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.374 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'net.devh.springboot.autoconfigure.grpc.client.GrpcClientAutoConfiguration' of type [net.devh.springboot.autoconfigure.grpc.client.GrpcClientAutoConfiguration$$EnhancerBySpringCGLIB$$e3d45cc0] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.660 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.stream.config.SpelExpressionConverterConfiguration' of type [org.springframework.cloud.stream.config.SpelExpressionConverterConfiguration$$EnhancerBySpringCGLIB$$d28f5c61] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.681 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spelConverter' of type [org.springframework.cloud.stream.config.SpelExpressionConverterConfiguration$SpelConverter] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.703 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'grpcChannelsProperties' of type [net.devh.springboot.autoconfigure.grpc.client.GrpcChannelsProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.716 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'grpcLoadBalancerFactory' of type [io.grpc.util.RoundRobinLoadBalancerFactory] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.738 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'net.devh.springboot.autoconfigure.grpc.client.GrpcClientAutoConfiguration$TraceClientAutoConfiguration' of type [net.devh.springboot.autoconfigure.grpc.client.GrpcClientAutoConfiguration$TraceClientAutoConfiguration$$EnhancerBySpringCGLIB$$3a8c93dd] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.765 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spring.sleuth-org.springframework.cloud.sleuth.autoconfig.SleuthProperties' of type [org.springframework.cloud.sleuth.autoconfig.SleuthProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.770 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.autoconfig.TraceAutoConfiguration' of type [org.springframework.cloud.sleuth.autoconfig.TraceAutoConfiguration$$EnhancerBySpringCGLIB$$b50217f] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.809 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'defaultSpanAdjuster' of type [org.springframework.cloud.sleuth.NoOpSpanAdjuster] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.812 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.stream.SleuthStreamAutoConfiguration' of type [org.springframework.cloud.sleuth.stream.SleuthStreamAutoConfiguration$$EnhancerBySpringCGLIB$$aca7b1fe] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.836 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spring.sleuth.sampler-org.springframework.cloud.sleuth.sampler.SamplerProperties' of type [org.springframework.cloud.sleuth.sampler.SamplerProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.845 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'defaultTraceSampler' of type [org.springframework.cloud.sleuth.sampler.PercentageBasedSampler] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.854 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'randomForSpanIds' of type [java.util.Random] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.901 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spanNamer' of type [org.springframework.cloud.sleuth.DefaultSpanNamer] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.930 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.log.SleuthLogAutoConfiguration$Slf4jConfiguration' of type [org.springframework.cloud.sleuth.log.SleuthLogAutoConfiguration$Slf4jConfiguration$$EnhancerBySpringCGLIB$$58bb2b4d] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:20:59.984 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spring.sleuth.log.slf4j-org.springframework.cloud.sleuth.log.SleuthSlf4jProperties' of type [org.springframework.cloud.sleuth.log.SleuthSlf4jProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.014 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'slf4jSpanLogger' of type [org.springframework.cloud.sleuth.log.Slf4jSpanLogger] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.050 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration' of type [org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration$$EnhancerBySpringCGLIB$$88a8803c] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.098 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'serverProperties' of type [org.springframework.boot.autoconfigure.web.ServerProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.249 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spring.zipkin-org.springframework.cloud.sleuth.stream.ZipkinProperties' of type [org.springframework.cloud.sleuth.stream.ZipkinProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.267 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.commons.util.UtilAutoConfiguration' of type [org.springframework.cloud.commons.util.UtilAutoConfiguration$$EnhancerBySpringCGLIB$$9a00cdf0] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.308 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'inetUtilsProperties' of type [org.springframework.cloud.commons.util.InetUtilsProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.321 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'inetUtils' of type [org.springframework.cloud.commons.util.InetUtils] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.329 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.stream.SleuthStreamAutoConfiguration$DefaultEndpointLocatorConfiguration' of type [org.springframework.cloud.sleuth.stream.SleuthStreamAutoConfiguration$DefaultEndpointLocatorConfiguration$$EnhancerBySpringCGLIB$$7f66c510] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.346 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'zipkinEndpointLocator' of type [org.springframework.cloud.sleuth.stream.ServerPropertiesHostLocator] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.355 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.metric.TraceMetricsAutoConfiguration$CounterServiceSpanReporterConfig' of type [org.springframework.cloud.sleuth.metric.TraceMetricsAutoConfiguration$CounterServiceSpanReporterConfig$$EnhancerBySpringCGLIB$$847edcbf] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.376 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.boot.actuate.autoconfigure.MetricRepositoryAutoConfiguration$FastMetricServicesConfiguration' of type [org.springframework.boot.actuate.autoconfigure.MetricRepositoryAutoConfiguration$FastMetricServicesConfiguration$$EnhancerBySpringCGLIB$$b9b668bb] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.408 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'counterBuffers' of type [org.springframework.boot.actuate.metrics.buffer.CounterBuffers] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.429 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'counterService' of type [org.springframework.boot.actuate.metrics.buffer.BufferCounterService] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.438 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.metric.TraceMetricsAutoConfiguration' of type [org.springframework.cloud.sleuth.metric.TraceMetricsAutoConfiguration$$EnhancerBySpringCGLIB$$f8dd104d] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.457 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'sleuthMetricProperties' of type [org.springframework.cloud.sleuth.metric.SleuthMetricProperties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.479 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spanReporterCounterService' of type [org.springframework.cloud.sleuth.metric.CounterServiceBasedSpanMetricReporter] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.551 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'sleuthStreamSpanReporter' of type [org.springframework.cloud.sleuth.stream.StreamSpanReporter] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.629 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'spring.sleuth.keys-org.springframework.cloud.sleuth.TraceKeys' of type [org.springframework.cloud.sleuth.TraceKeys] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.658 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'sleuthTracer' of type [org.springframework.cloud.sleuth.trace.DefaultTracer] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.706 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'globalTraceClientInterceptorConfigurerAdapter' of type [net.devh.springboot.autoconfigure.grpc.client.GrpcClientAutoConfiguration$TraceClientAutoConfiguration$1] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.723 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'globalClientInterceptorRegistry' of type [net.devh.springboot.autoconfigure.grpc.client.GlobalClientInterceptorRegistry] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.751 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'addressChannelFactory' of type [net.devh.springboot.autoconfigure.grpc.client.AddressChannelFactory] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.880 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'integrationGlobalProperties' of type [org.springframework.beans.factory.config.PropertiesFactoryBean] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:00.893 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'integrationGlobalProperties' of type [java.util.Properties] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:01.060 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.stream.config.BindingServiceConfiguration$PostProcessorConfiguration' of type [org.springframework.cloud.stream.config.BindingServiceConfiguration$PostProcessorConfiguration$$EnhancerBySpringCGLIB$$941aa271] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:01.122 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.instrument.async.AsyncDefaultAutoConfiguration' of type [org.springframework.cloud.sleuth.instrument.async.AsyncDefaultAutoConfiguration$$EnhancerBySpringCGLIB$$ba36b08b] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2017-10-01 20:21:01.148 INFO [demo-cloud-sleuth,,,] 25806 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.sleuth.instrument.web.client.TraceWebClientAutoConfiguration$TraceOAuthConfiguration' of type [org.springframework.cloud.sleuth.instrument.web.client.TraceWebClientAutoConfiguration$TraceOAuthConfiguration$$EnhancerBySpringCGLIB$$174f96cb] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
I'll later try to provide a patch to fix the issue I encountered above.