  Background: The proliferation of cloud providers and provisioning levels has
opened a space for cloud brokerage services. Brokers intermediate between cloud
customers and providers to assist the customer in selecting the most suitable
cloud service, helping to manage the dimensionality, heterogeneity, and
uncertainty associated with cloud services. Objective: This paper identifies
and classifies approaches to realise cloud brokerage. By doing so, this paper
presents an understanding of the state of the art and a novel taxonomy to
characterise cloud brokers. Method: We conducted a systematic literature survey
to compile studies related to cloud brokerage and explore how cloud brokers are
engineered. We analysed the studies from multiple perspectives, such as
motivation, functionality, engineering approach, and evaluation methodology.
Results: The survey resulted in a knowledge base of current proposals for
realising cloud brokers. The survey identified surprising differences between
the studies' implementations, with engineering efforts directed at combinations
of market-based solutions, middlewares, toolkits, algorithms, semantic
frameworks, and conceptual frameworks. Conclusion: Our comprehensive
meta-analysis shows that cloud brokerage is still a formative field. There is
no doubt that progress has been achieved in the field but considerable
challenges remain to be addressed. This survey identifies such challenges and
directions for future research.
