  Along with the wide-adoption of Serverless Computing, more and more
applications are developed and deployed on cloud platforms. Major cloud
providers present their serverless workflow services to orchestrate serverless
functions, making it possible to perform complex applications effectively. A
comprehensive instruction is necessary to help developers understand the pros
and cons, and make better choices among these serverless workflow services.
However, the characteristics of these serverless workflow services have not
been systematically analyzed. To fill the knowledge gap, we survey four
mainstream serverless workflow services, investigating their characteristics
and performance. Specifically, we review their official documents and compare
them in terms of seven dimensions including programming model, state
management, etc. Then, we compare the performance (i.e., execution time of
functions, execution time of workflows, orchestration overhead of workflows)
under various experimental settings considering activity complexity and
data-flow complexity of workflows, as well as function complexity of serverless
functions. Finally, we discuss and verify the service effectiveness for two
actual workloads. Our findings could help application developers and serverless
providers to improve the development efficiency and user experience.
