APM Sling MDC

MDCLoggerFilter.java

package com.example

import co.elastic.apm.api.ElasticApm;
import org.apache.felix.scr.annotations.sling.SlingFilter;
import org.apache.felix.scr.annotations.sling.SlingFilterScope;
import org.apache.sling.api.SlingHttpServletRequest;
import org.slf4j.MDC;

import javax.servlet.*;
import java.io.IOException;
/**
 * The SlingFilterScope.REQUEST is important as MDC needs to be configured prior
 * to any logger being executed in the page rendering.
 */
@SlingFilter(
        label = "APM MDC Filter",
        description = "Elastic APM MDC filter to get IDs",
        order = 0,
        scope = {SlingFilterScope.REQUEST})
public class MDCLoggerFilter implements javax.servlet.Filter{
    public static final String TRACE_ID = "trace.id";
    public static final String TRANSACTION_ID = "transaction.id";
    public static final String SPAN_ID = "span.id";

    private static final String[] MDC_CUSTOM_KEYS = {
            TRACE_ID,
            TRANSACTION_ID,
            SPAN_ID,
    };

    public void init(FilterConfig filterConfig) throws ServletException {
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                         FilterChain filterChain) throws IOException, ServletException {
        final SlingHttpServletRequest request = (SlingHttpServletRequest) servletRequest;
        try {
            insertIntoMDC(request);
            filterChain.doFilter(request, servletResponse);
        } finally {
            clearMDC();
        }
    }

    private void clearMDC() {
        for (String key : MDC_CUSTOM_KEYS) {
            MDC.remove(key);
        }
    }

    private void insertIntoMDC(SlingHttpServletRequest request) {
        //logic can go here to take value from request object.
        // Can also utilize ResourceResolver from same request.
        // If needed, can also write a generic OSGi Configuration
        // (String Array Properties) to read from standard request objects,
        // i.e cookies, headers, and parameters.
        MDC.put(TRACE_ID, ElasticApm.currentTransaction().getTraceId());
        MDC.put(TRANSACTION_ID, ElasticApm.currentTransaction().getId());
        MDC.put(SPAN_ID, ElasticApm.currentSpan().getId());
    }

    public void destroy() {
    }
}