Dropwizard: Documentation to create custom logging appenders

Created on 16 Jul 2019 · 6Comments · Source: dropwizard/dropwizard

There are some place that contains the documentation for create my own logging appender? I saw some examples in the internet, but it is a few difficult to understand.

stale

Source

danielborges93

Most helpful comment

Here is an example of creating a custom console appender to add a header and footer:

@JsonTypeName("my-console")
public class MyConsoleAppender<E extends DeferredProcessingAware> extends ConsoleAppenderFactory<E> {
    @Override
    protected OutputStreamAppender<E> appender(LoggerContext context) {
        final OutputStreamAppender<E> appender = super.appender(context);
        appender.setEncoder(new EncoderBase<E>() {
            @Override
            public byte[] headerBytes() {
                return "this is a header\n".getBytes(StandardCharsets.UTF_8);
            }

            @Override
            public byte[] encode(E event) {
                return event.toString().getBytes(StandardCharsets.UTF_8);
            }

            @Override
            public byte[] footerBytes() {
                return "this is a footer\n".getBytes(StandardCharsets.UTF_8);
            }
        });
        return appender;
    }
}

Then create file: resources/META-INF/services/io.dropwizard.logging.AppenderFactory and add the appender to it:

com.example.MyConsoleAppender

You'll be able to reference it in yaml

level: INFO
appenders:
  - type: my-console

nickbabcock on 8 Aug 2019

👍3

All 6 comments

@danielborges93 What do you want to achieve?

joschi on 16 Jul 2019

@joschi I whant create new logging appenders to use in my project. For example, an Slack appender, a Github/GitLab/Bitbucket issue creator for error logs, a custom DBAppernder.

What files I should create? What classes I should extend? What interface I should implement? What means the parameters of build method of AbstractAppenderFactory?

Like a setp-by-step tutorial to create new appenders.

danielborges93 on 16 Jul 2019

Here is an example of creating a custom console appender to add a header and footer:

@JsonTypeName("my-console")
public class MyConsoleAppender<E extends DeferredProcessingAware> extends ConsoleAppenderFactory<E> {
    @Override
    protected OutputStreamAppender<E> appender(LoggerContext context) {
        final OutputStreamAppender<E> appender = super.appender(context);
        appender.setEncoder(new EncoderBase<E>() {
            @Override
            public byte[] headerBytes() {
                return "this is a header\n".getBytes(StandardCharsets.UTF_8);
            }

            @Override
            public byte[] encode(E event) {
                return event.toString().getBytes(StandardCharsets.UTF_8);
            }

            @Override
            public byte[] footerBytes() {
                return "this is a footer\n".getBytes(StandardCharsets.UTF_8);
            }
        });
        return appender;
    }
}

Then create file: resources/META-INF/services/io.dropwizard.logging.AppenderFactory and add the appender to it:

com.example.MyConsoleAppender

You'll be able to reference it in yaml

level: INFO
appenders:
  - type: my-console

nickbabcock on 8 Aug 2019

👍3

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 14 days

github-actions[bot] on 19 Aug 2019

@nickbabcock do you have any idea why this wouldn't work? I'm trying to create a stack driver appender that will basically append a traceId to all the logs. This is done via com.google.cloud.logging.TraceLoggingEnhancer

I'm not seeing the trace ID appended to any of the logs

import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.core.Appender;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonTypeName;
import com.google.cloud.logging.logback.LoggingAppender;
import io.dropwizard.logging.AbstractAppenderFactory;
import io.dropwizard.logging.async.AsyncAppenderFactory;
import io.dropwizard.logging.filter.LevelFilterFactory;
import io.dropwizard.logging.layout.LayoutFactory;

@JsonTypeName("stack-driver-console")
public class StackDriverAppenderFactory extends AbstractAppenderFactory {

  private String appenderName = "stack-driver-console-appender";
  private boolean includeContextName = true;

  @JsonProperty
  public String getName() {
    return this.appenderName;
  }

  @JsonProperty
  public void setName(String name) {
    this.appenderName = name;
  }

  @Override
  public Appender build(
    LoggerContext loggerContext,
    String s,
    LayoutFactory layoutFactory,
    LevelFilterFactory levelFilterFactory,
    AsyncAppenderFactory asyncAppenderFactory) {

    setNeverBlock(true);
    setTimeZone("utc");
    setLogFormat("%-6level [%d{HH:mm:ss.SSS}] [%t] %logger{5} - %X{code} %msg %n");

    LoggingAppender cloudAppender = new LoggingAppender();
    cloudAppender.addEnhancer("com.google.cloud.logging.TraceLoggingEnhancer");
    cloudAppender.addFilter(levelFilterFactory.build(Level.toLevel(getThreshold())));

    cloudAppender.setFlushLevel(Level.WARN);
    cloudAppender.setLog("application.log");

    cloudAppender.setName(appenderName);
    cloudAppender.setContext(loggerContext);
    cloudAppender.start();

    return wrapAsync(cloudAppender, asyncAppenderFactory);
  }
}