shaonan666 commented on issue #3569:
URL:
https://github.com/apache/logging-log4j2/issues/3569#issuecomment-2754340901
I think I’ve got it. Let me describe what happened again to ensure I fully
understand.
**My program doesn’t specify a `messageFactory`.**
In version 2.23.1, `LoggerContext#getLogger(String name) `ultimately
initializes a `ParameterizedMessageFactory`
https://github.com/apache/logging-log4j2/blob/fea2a7116160fb1555d578406444b4fc4f0ef2da/log4j-core/src/main/java/org/apache/logging/log4j/core/LoggerContext.java#L493-L495
https://github.com/apache/logging-log4j2/blob/fea2a7116160fb1555d578406444b4fc4f0ef2da/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java#L134-L137
In version 2.24.3, `LoggerContext#getLogger(String name) ` uses a
GC-free-compliant `ReusableMessageFactory` based on the configuration
`log4j2.enableThreadlocals=true`
https://github.com/apache/logging-log4j2/blob/4aa5efec7f2ee2d4623381cd66c3df3a16a6b9a9/log4j-core/src/main/java/org/apache/logging/log4j/core/LoggerContext.java#L93-L97
https://github.com/apache/logging-log4j2/blob/4aa5efec7f2ee2d4623381cd66c3df3a16a6b9a9/log4j-core/src/main/java/org/apache/logging/log4j/core/LoggerContext.java#L538-L540
These two different MessageFactory implementations are the main reason I’ve
observed a gradual increase in memory usage: to support GC-free,
`ReusableMessageFactory` allocates objects that aren’t released until all
`RingBufferLogEvent` instances have been used at least once, at which point the
memory growth stops.
---
>Do you expect Log4j Core to pre-allocate StringBuilders of size
[log4j2.initialReusableMsgSize](https://logging.apache.org/log4j/2.x/manual/garbagefree.html#log4j2.initialReusableMsgSize)
instead of doing it on-demand?
Pre-allocating a suitably sized `StringBuilder` based on prediction could be
a good choice for services with high runtime latency requirements. But my main
concern is the gradual memory increase in version 2.24.3, which I didn’t see in
2.23.1, and I initially suspected a memory leak. However, based on the current
situation, it doesn’t seem to be a memory leak risk. I’m considering reducing
the RingBuffer size to manage memory usage.
Thank you for your patient explanations!
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