in lib/ecs_logging/formatter.rb [24:38]
def call(severity, time, progname, msg, **extras)
base = {
"@timestamp": time.utc.iso8601(3),
"log.level": severity,
"message": msg,
"ecs.version": "1.4.0"
}
base['log.logger'] = progname if progname
base.merge!(extras) if extras
JSON.fast_generate(base) + "\n"
end