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WSO2 Message Broker, primarily supports memory-based flow controlling. You can configure an MB server instance using two parameters; <globalMemoryTreshold> (default value is 0.4) and <globalMemoryRecoveryThreshold> (default value is 0.5). The global memory threshold is the memory threshold at which flow controlling is enabled, whereas the global memory recovery threshold is the memory threshold at which flow controlling is disabled and message publishing is resumed. The rate at which messages are transmitted is controlled by exerting back-pressure when the defined global memory threshold or message count threshold per connection exceeds. At this point, message acceptance is blocked temporarily until the producer is notified of memory recovery. In the meantime, a background process constantly checks whether the memory is recovered, and when the memory is available, the producer is notified and can resume sending messages to the server. Flow control configurations are defined in the <MB_HOME>/repository/conf/advanced/andes-config.xml file.
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