@Override
    public void notify(final ConfigChangeEvent value) {
        String newValue;
        if (EventType.DELETE.equals(value.getEventType())) {
            this.content = null;
            newValue = null;
        } else {
            this.content = value.getNewValue();
            newValue = value.getNewValue();
        }
        try {
            if (!reconfigure(newValue)) {
                return;
            }
        } catch (Throwable t) {
            log.error("failed to apply configuration to log4j", t);
            return;
        }
    }
LoggingConfigWatcher watches the change of logging configuration. Once got the change content, it would apply them to
the current logger context.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/logging/LoggingConfigWatcher.java