Gson Log4J2 JSON Layout

Log4J2 JSON layout generated and sanitized using Gson. This library has dependencies on gson and log4j-core.

Import from Maven Central:

pom.xml

<dependency>
    <groupId>com.github.mvh77</groupId>
    <artifactId>gson-log4j2-layout</artifactId>
    <version>1.1.0</version>
</dependency>

Use it in your log4j2.xml file with <GsonJsonLayout/> and be sure to add packages="com.github.mvh77.log4j2layout" to the configuration.

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="info" name="spring-boot-kafka-log"
                             packages="com.github.mvh77.log4j2layout">
    <Appenders>
        <Kafka name="Kafka" topic="system.logging" key="test-app">
            <GsonJsonLayout/>
            <Property name="bootstrap.servers">kafka-1:9092</Property>
        </Kafka>
        <Async name="Async">
            <AppenderRef ref="Kafka"/>
        </Async>

        <Console name="stdout" target="SYSTEM_OUT">
            <GsonJsonLayout pretty="true"/>
        </Console>

    </Appenders>
    <Loggers>
        <Root level="INFO">
            <AppenderRef ref="Kafka"/>
            <AppenderRef ref="stdout"/>
        </Root>
        <!-- MUST BE INFO OR GREATER TO PREVENT RECURSIVE LOGGING -->
        <Logger name="org.apache.kafka" level="WARN" />
    </Loggers>
</Configuration>

Table 1. Layout Configuration

Attribute	Default	Description
charset	UTF-8	Charset to use (probably always UTF-8)
pretty	false	Pretty printed JSON
json-stacktrace	false	Format stack traces as JSON
max-stack-size	20	Maximum number of nested exceptions
logger-pattern	none	The conversion pattern for the name of the logger value, for example '1.' would rename the logger from org.apache.commons.Foo to o.a.c.Foo. See Patterns in PatternLayout.

Example JSON that has an exception with a root cause. Implemented with Elastic Stack in mind (@timestamp).

Example log

{
  "@timestamp": "2018-12-07T11:15:33.350Z",
  "thread": "main",
  "level": "WARN",
  "logger": "hello.Application",
  "message": "here\u0027s an exception",
  "stack-trace": [
    {
      "exception": "java.lang.RuntimeException",
      "message": "test",
      "frames": [
        "at hello.Application.run(Application.java:31)",
        "at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:813)",
        "at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:797)",
        "at org.springframework.boot.SpringApplication.run(SpringApplication.java:324)",
        "at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260)",
        "at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248)",
        "at hello.Application.main(Application.java:24)"
      ]
    },
    {
      "caused by": "java.lang.IllegalStateException",
      "message": "root cause",
      "frames": [
        "at hello.Application.run(Application.java:31)",
        "at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:813)",
        "at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:797)",
        "at org.springframework.boot.SpringApplication.run(SpringApplication.java:324)",
        "at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260)",
        "at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248)",
        "at hello.Application.main(Application.java:24)"
      ]
    }
  ]
}