Echopraxia

Echopraxia is a Java logging API designed around structured logging, rich context, and conditional logging. There are Logback and Log4J2 implementations, but Echopraxia's API is completely dependency-free, meaning it can be implemented with any logging API, i.e. jboss-logging, JUL, JEP 264, or even directly.

What this means is that all arguments in a logging statement have a name and a value, for example:

logger.info("arg1 is {} and arg2 is {}", fb -> fb.list(
  fb.string("name", "value"),
  fb.number("age", 13)
));

writes out in logfmt as:

INFO 13.232 arg1 is name=value and arg2 is age=13

and in a JSON format as:

{
  "message": "arg1 is name=value and arg2 is age=13",
  "name": "value",
  "age": 13
}

What makes Echopraxia effective -- especially for debugging -- is that you can define your own field builders to map between objects and fields, and then pass in your own objects and render complex objects. For example, we can render a Person object:

Logger<PersonFieldBuilder> logger = LoggerFactory
                                        .getLogger(getClass())
                                        .withFieldBuilder(PersonFieldBuilder.instance());

Person abe = new Person("Abe", 1, "yodelling");
abe.setFather(new Person("Bert", 35, "keyboards"));
abe.setMother(new Person("Candace", 30, "iceskating"));

logger.info("{}", fb -> fb.person("abe", abe));

And print out the internal state of the Person in both logfmt and JSON.

INFO 13.223 abe={Abe, 1, father={Bert, 35, father=null, mother=null, interests=[keyboards]}, mother={Candace, 30, father=null, mother=null, interests=[iceskating]}, interests=[yodelling]}

Echopraxia also has a "contextual" logging feature that renders fields in JSON:

var fooLogger = logger.withFields(fb -> fb.string("foo", "bar"));
fooLogger.info("This logs the 'foo' field automatically in JSON");

And has conditional logging based on fields and exceptions using JSONPath:

Condition c = (level, ctx) ->
    ctx.findString("$.exception.stackTrace[0].methodName")
        .filter(s -> s.endsWith("Foo"))
        .isPresent();
logger.error(c, "Only render this error if method name ends in Foo", e);

And there is also a feature to change logging conditions dynamically using scripts.

Examples

For the fastest possible way to try out Echopraxia, download and run the JBang script.

Simple examples and integrations with dropwizard metrics and OSHI are available at echopraxia-examples.

For a web application example, see this Spring Boot Project.

Scala API

There is a Scala API available at https://github.com/tersesystems/echopraxia-plusscala.