Dropwizard with custom logback layout

echo.yaml

logging:
  level: INFO
  appenders:
    - type: production-stdout-json

io.dropwizard.logging.AppenderFactory

# put in META-INF/services/io.dropwizard.logging.AppenderFactory without this line
io.dropwizard.logging.ConsoleAppenderFactory
io.dropwizard.logging.FileAppenderFactory
io.dropwizard.logging.SyslogAppenderFactory
com.wire.bots.echo.ProductionAppender

JsonLoggingLayout.java

package com.wire.bots.echo;

import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.CoreConstants;
import ch.qos.logback.core.LayoutBase;

import java.time.Instant;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;
import java.util.Map;

/**
 * Layout used on Wire production services in the ELK stack.
 */
public class JsonLoggingLayout extends LayoutBase<ILoggingEvent> {

    private static final DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ISO_DATE_TIME.withZone(ZoneOffset.UTC);

    @Override
    public String doLayout(ILoggingEvent event) {
        StringBuffer buffer = new StringBuffer(256);
        buffer.append("{");

        appendJson(buffer, "@timestamp", formatTime(event));

        Map<String, String> mdc = event.getMDCPropertyMap();
        if (mdc.containsKey("infra_request")) {
            appendJson(buffer, "infra_request", mdc.get("infra_request"));
        }

        if (mdc.containsKey("app_request")) {
            appendJson(buffer, "app_request", mdc.get("app_request"));
        }

        appendJson(buffer, "logger", event.getLoggerName());
        appendJson(buffer, "message", event.getFormattedMessage());
        appendJson(buffer, "level", event.getLevel().levelStr);
        appendJson(buffer, "thread_name", event.getThreadName(), "");

        buffer.append("}")
                .append(CoreConstants.LINE_SEPARATOR);

        return buffer.toString();
    }

    private void appendJson(StringBuffer buffer, String key, String value) {
        appendJson(buffer, key, value, ",");
    }

    private void appendJson(StringBuffer buffer, String key, String value, String ending) {
        buffer.append("\"")
                .append(key)
                .append("\":\"")
                .append(value)
                .append("\"")
                .append(ending);
    }

    private String formatTime(ILoggingEvent event) {
        return dateTimeFormatter.format(Instant.ofEpochMilli(event.getTimeStamp()));
    }
}

ProductionAppender.java

package com.wire.bots.echo;

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.Appender;
import ch.qos.logback.core.ConsoleAppender;
import com.fasterxml.jackson.annotation.JsonTypeName;
import io.dropwizard.logging.AbstractAppenderFactory;
import io.dropwizard.logging.async.AsyncAppenderFactory;
import io.dropwizard.logging.filter.LevelFilterFactory;
import io.dropwizard.logging.layout.LayoutFactory;

/**
 * Production console appender using JsonLoggingLayout.
 */
@JsonTypeName("production-stdout-json")
public class ProductionAppender extends AbstractAppenderFactory<ILoggingEvent> {

    @Override
    public Appender<ILoggingEvent> build(
            LoggerContext context,
            String applicationName,
            LayoutFactory<ILoggingEvent> layoutFactory,
            LevelFilterFactory<ILoggingEvent> levelFilterFactory,
            AsyncAppenderFactory<ILoggingEvent> asyncAppenderFactory
    ) {
        ConsoleAppender<ILoggingEvent> appender = new ConsoleAppender<>();
        appender.setContext(context);
        appender.setTarget("System.out");

        JsonLoggingLayout l = new JsonLoggingLayout();
        l.start();

        appender.setLayout(l);
        appender.start();
        return appender;
    }
}