in invoker/core/src/main/java/com/google/cloud/functions/invoker/runner/Invoker.java [88:99]
static {
if (isGcf()) {
// If we're running with Google Cloud Functions, we'll get better-looking logs
// if we arrange for them to be formatted using StackDriver's "structured
// logging" JSON format. Remove the JDK's standard logger and replace it with
// the JSON one.
for (Handler handler : rootLogger.getHandlers()) {
rootLogger.removeHandler(handler);
}
rootLogger.addHandler(new JsonLogHandler(System.out, false));
}
}