I'm resending this letter to the mail list as we hit the message size limit. :)
Hello Michal!
I have some good news.
We have found the reason for the increasing memory usage of syslog-ng in amqp() driver.
It is due to our internal memory handling method (aka scratch_buffers) which we use in performance critical paths to prevent the overhead of memory allocations/deallocations of GStrings. It is using memory from a pre-allocated pool instead of allocating/freeing.
As I have described before, the memory usage only increases if the number of queued messages reaches a new maximum.
It is not per message and does not happen every for every queued message.
We have several options how to fix this issue and will soon share one.