[LOG4J2-2034] In async mode JsonLayout can't serialize an event with self referenced throwable

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.8.2, 2.9.0
• Component/s: Layouts
• Assignee: Unassigned
• Reporter: Leonid Bogdanov
• Created: 07/Sep/17 03:55
• Updated: 14/Sep/17 20:08

Description

When async logging is configured, JsonLayout cannot serialize a log event in which provided Throwable has a self-reference. For example, this may be the case for many Spring exceptions inherited from org.springframework.core.NestedRuntimeException or org.springframework.core.NestedCheckedException classes via getMostSpecificCause() method.

The root cause of the bug is org.apache.logging.log4j.core.async.RingBufferLogEvent.getThrowable() method, it isn't marked as ignored by Jackson serializer, so when the Throwable in a log event contains a self-reference, Jackson blows up with an exception

2017-09-07 13:28:08,799 Log4j2-TF-1-AsyncLogger[AsyncContext@6bc7c054]-1 ERROR com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Direct self-reference leading to cycle (through reference chain: org.apache.logging.log4j.core.async.RingBufferLogEvent["throwable"]->org.log4j.App$SelfReferencedException["mostSpecificCause"]) com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Direct self-reference leading to cycle (through reference chain: org.apache.logging.log4j.core.async.RingBufferLogEvent["throwable"]->org.log4j.App$SelfReferencedException["mostSpecificCause"])
	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77)
	at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1191)
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter._handleSelfReference(BeanPropertyWriter.java:944)
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:721)
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
	at com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter.serializeAsField(SimpleBeanPropertyFilter.java:208)
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFieldsFiltered(BeanSerializerBase.java:771)
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:153)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
	at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1396)
	at com.fasterxml.jackson.databind.ObjectWriter._configAndWriteValue(ObjectWriter.java:1120)
	at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:966)
	at org.apache.logging.log4j.core.layout.AbstractJacksonLayout.toSerializable(AbstractJacksonLayout.java:213)
	at org.apache.logging.log4j.core.layout.JsonLayout.toSerializable(JsonLayout.java:254)
	at org.apache.logging.log4j.core.layout.AbstractJacksonLayout.toSerializable(AbstractJacksonLayout.java:193)
	at org.apache.logging.log4j.core.layout.JsonLayout.toSerializable(JsonLayout.java:60)
	at org.apache.logging.log4j.core.layout.AbstractJacksonLayout.toSerializable(AbstractJacksonLayout.java:34)
	at org.apache.logging.log4j.core.layout.AbstractStringLayout.toByteArray(AbstractStringLayout.java:299)
	at org.apache.logging.log4j.core.layout.AbstractLayout.encode(AbstractLayout.java:210)
	at org.apache.logging.log4j.core.layout.AbstractLayout.encode(AbstractLayout.java:37)
...

One possible workaround is to create a custom Layout which delegates necessary calls to the original JsonLayout catching possible JsonProcessingException - when the latter is actually caught, another attempt to serialize a LogEvent is made, but this time instead of the original log event object a Log4jLogEvent.createMemento(originalEvent) copy is serialized.

The potential fix for the core JsonLayout class would be to configure Jackson to ignore RingBufferLogEvent.getThrowable()?