event-bus/distributed/src/main/java/org/apache/james/events/ListenerExecutor.java

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package org.apache.james.events;

import static org.apache.james.events.EventBus.Metrics.timerName;

import org.apache.james.metrics.api.MetricFactory;
import org.apache.james.util.MDCBuilder;
import org.apache.james.util.ReactorUtils;

import reactor.core.publisher.Mono;

class ListenerExecutor {
    private final MetricFactory metricFactory;

    ListenerExecutor(MetricFactory metricFactory) {
        this.metricFactory = metricFactory;
    }

    Mono<Void> execute(EventListener.ReactiveEventListener listener, MDCBuilder mdcBuilder, Event event) {
        if (listener.isHandling(event)) {
            return Mono.from(metricFactory.decoratePublisherWithTimerMetric(timerName(listener),
                Mono.from(listener.reactiveEvent(event))
                    .subscriberContext(ReactorUtils.context("ListenerExecutor", mdc(listener, mdcBuilder, event)))));
        }
        return Mono.empty();
    }

    private MDCBuilder mdc(EventListener listener, MDCBuilder mdcBuilder, Event event) {
        return mdcBuilder
            .addToContext(EventBus.StructuredLoggingFields.EVENT_ID, event.getEventId().getId().toString())
            .addToContext(EventBus.StructuredLoggingFields.EVENT_CLASS, event.getClass().getCanonicalName())
            .addToContext(EventBus.StructuredLoggingFields.USER, event.getUsername().asString())
            .addToContext(EventBus.StructuredLoggingFields.LISTENER_CLASS, listener.getClass().getCanonicalName());
    }
}