add paragraph anout kafka in billoing

Author: mksahakyan

release-notes-11.2

@@ -82,6 +82,18 @@ HTML header: <title>dCache 11.2 Release Notes</title>
 
 The transferTag is used by clients to label transfers with activity-specific information, such as experiment ID and workflow ID. This information is currently provided by XRootD and HTTP clients, and can be used by monitoring systems to identify data flows. Starting version 11.2.0 dCache includes transferTag information into the generated JSON records.
 
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+
+A Kafka producer operates asynchronously by default: when an application calls send(), the record is placed into an internal buffer and the call typically returns immediately, without waiting for broker acknowledgements.
+
+However, asynchronous operation does not guarantee fully non-blocking behavior. Under certain conditions—such as broker unavailability, missing topic metadata, or exhausted producer buffers—the producer may block or fail synchronously. These edge cases are a common source of confusion and can lead to unexpected application failures.
+
+In dCache, this behavior poses a risk when Kafka is unavailable, as transfer events may not be marked as successful if Kafka reporting fails, potentially causing service instability or crashes. To mitigate this risk, Kafka logging has been relocated to the non-blocking Billing service and disabled in other dCache components that may block on Kafka availability. As a result, Kafka cluster outages no longer impact the stability of dCache processes.
+
+To enable kafka for billing service the folowwing property in `billing.properties` should be enabled 
+`(one-of?true|false|${dcache.billing.enable.kafka})billing.enable.kafka`.
+
+
 ### Chimera
 
 ### Cleaner