Add reactive application with database and Kafka

[mfvanek]

import io.micrometer.tracing.handler.TracingObservationHandler.TracingContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.server.reactive.observation.ServerRequestObservationContext;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
import reactor.core.publisher.Mono;

public class TraceIdInResponseReactiveFilter implements WebFilter {

    private static final Logger logger = LoggerFactory.getLogger(TraceIdInResponseReactiveFilter.class);

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
        exchange.getResponse().beforeCommit(() -> {
            final ServerRequestObservationContext observationContext = exchange.getAttribute(ServerRequestObservationContext.CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE);
            if (observationContext != null) {
                final TracingContext traceContext = observationContext.get(TracingContext.class);
                if (traceContext != null) {
                    final String traceId = traceContext.getSpan().context().traceId();
                    exchange.getResponse().getHeaders().add("X-Trace-Id", traceId);
                    logger.debug("Added TraceId: {} to the response", traceId);
                }
            }
            return Mono.empty();
        });
        return chain.filter(exchange);
    }
}

spring:
  reactor:
    context-propagation: auto # Important!!!