Troubleshooting ActiveMQ Producer Flow Control Blocks
The alert comes in at 2 AM: your order processing service is unresponsive. The application is not crashed, threads are running, the JVM is healthy, but no messages are being sent. Your operations team traces it to a blocked send() call on an ActiveMQ connection. Hours later, after restarting the application, someone finds this line in the broker log from 11 PM the previous day.