  Operating a scalable and reliable server application, such as
publish/subscribe (pub/sub) systems, requires tremendous development efforts
and resources. The emerging serverless paradigm simplifies the development and
deployment of highly available applications by delegating most operational
concerns to the cloud providers. The serverless paradigm describes a
programming model where the developers break the application downs into smaller
microservices that run on the cloud in response to events. This paper proposes
designing a serverless pub/sub system based on the IBM Bluemix cloud platform.
Our pub/sub system performs topic-based, content-based, and function-based
matchings. The function-based matching is a novel matching approach where the
subscribers can define a highly customizable subscription function that the
broker applies to the publications in the cloud. The evaluations of the
designed system verify the practicality of the designed system. However, the
vendor-specific constraints of the IBM Bluemix resources are a bottleneck to
the scalability of the broker.
