Another point is that for any asynchronous appender implementation, it's a sine
qua non that the LoggingEvent class be thread-safe.
At least for the manipulations an appender might do: layout, accessing
properties, fixing properties.
I had a quick browse through the source and found what looks to me like a race
condition here:
public object LookupProperty(string key)
{
if (m_data.Properties != null)
{
return m_data.Properties[key];
}
if (m_compositeProperties == null)
{
CreateCompositeProperties();
}
return m_compositeProperties[key];
}
private void CreateCompositeProperties()
{
m_compositeProperties = new CompositeProperties();
if (m_eventProperties != null)
{
m_compositeProperties.Add(m_eventProperties);
}
... etc
If two threads call LookupProperty concurrently, one may start executing
CreateCompositeProperties and the other might access m_compositeProperties
before it's fully created.
If I'm right, the fix is simple - don't set m_compositeProperties until it's
completely created.
