Logback - how can you tell AsyncAppender's queue is full and starts dropping events?

Question

Is there a way to know that logback is discarding logging events because the queue is full? Is it logged anywhere?

Answer 1

There is no direct way to do it.

The Appender silently discards event:

AsyncAppenderBase.java

    @Override
    protected void append(E eventObject) {
        if (isQueueBelowDiscardingThreshold() && isDiscardable(eventObject)) {
            return;
        }
        preprocess(eventObject);
        put(eventObject);
    }

However, you can create your own appender by extending AsyncAppenderBase or AsyncAppender and override append method with your custom logic.