With single ILoggingEvent.getFormattedMessage() is null logging becomes completely broken

[gavenkoa]

Just do:

log.info(null);

and forget about delivering messages to ES until you reboot app ))

The problem is in:

            String formattedMessage = event.getFormattedMessage();
            if (settings.getMaxMessageSize() > 0 && formattedMessage.length() > settings.getMaxMessageSize()) {
                formattedMessage = formattedMessage.substring(0, settings.getMaxMessageSize()) + "..";
            }

formattedMessage.length() generates NPE.

AbstractElasticsearchPublisher is implemented in so shitty way that internals of JsonGenerator is stuck in broken state and can't heal.

JsonGenerator uses WriterBasedJsonGenerator and on

	private void serializeIndexString(JsonGenerator gen, T event) throws IOException {
		gen.writeStartObject();

writeStartObject() fail on internal check _verifyValueWrite("start an object"); as we are JsonWriteContext is at type == 2 and gotName == false so check fails:

    public int writeValue() {
        // Most likely, object:
        if (_type == TYPE_OBJECT) {
            if (!_gotName) {
                return STATUS_EXPECT_NAME;

In case of serialization errors JsonGenerator should be completely reinitialized or reset instead of reusing with broken intermediate state.

Following stacktrace is from a bit edited sources, ClassicElasticsearchPublisher is in original form:

java.lang.NullPointerException: null
	at com.internetitem.logback.elasticsearch.ClassicElasticsearchPublisher.serializeCommonFields(ClassicElasticsearchPublisher.java:37)
	at com.internetitem.logback.elasticsearch.ClassicElasticsearchPublisher.serializeCommonFields(ClassicElasticsearchPublisher.java:17)
	at com.internetitem.logback.elasticsearch.AbstractElasticsearchPublisher.serializeEvent(AbstractElasticsearchPublisher.java:211)
	at com.internetitem.logback.elasticsearch.AbstractElasticsearchPublisher.serializeEvents(AbstractElasticsearchPublisher.java:190)
	at com.internetitem.logback.elasticsearch.AbstractElasticsearchPublisher.run(AbstractElasticsearchPublisher.java:154)
	at java.base/java.lang.Thread.run(Thread.java:834)