A Distributed Publish/Subscribe System built on a DHT Substrate

Abstract

The publish/subscribe pattern is commonly found in messaging systems and message-oriented middleware. When large numbers of processes are publishing messages in applications where low latency and high throughput is needed, the performance of the messaging system is critical. Several solutions exist that provide high throughput and low latency to a high number of concurrent processes, such as RabbitMQ and Kafka. What happens to the performance of the system when each process also has a complex or large set of subscriptions? This is the case when users of an internet radio application notify each other of songs currently being played and the subscriptions of each user correspond to the user’s wish list – a list of songs that the user is interested in recording. This thesis examines how the popular messaging systems RabbitMQ and Kafka handle this situation when topic-based message filtering is used to model subscriptions. A prototype messaging system, Ingeborg, which is built on the key-value store Riak is also introduced and its performance is examined and compared to the previously mentioned systems. The results of the experimental study show that it is difficult to scale both RabbitMQ and Kafka with regards to the number of topics used, but that RabbitMQ shows greater flexibility in its configuration. Finally, the prototype system Ingeborg shows that it is possible to design a messaging system from scratch based on a key-value store, allowing even greater flexibility in prioritizing trade-offs and performance properties of a system.