Data centre networks are increasingly programmable,
with application-specific network services proliferating,
from custom load-balancers to middleboxes providing
caching and aggregation. Developers must currently implement
these services using traditional low-level APIs,
which neither support natural operations on application
data nor provide efficient performance isolation.
We describe FLICK, a framework for the programming
and execution of application-specific network services
on multi-core CPUs. Developers write network services
in the FLICK language, which offers high-level processing
constructs and application-relevant data types.
FLICK programs are translated automatically to efficient,
parallel task graphs, implemented in C++ on top of a
user-space TCP stack. Task graphs have bounded resource
usage at runtime, which means that the graphs
of multiple services can execute concurrently without
interference using cooperative scheduling. We evaluate
FLICK with several services (an HTTP load-balancer,
a Memcached router and a Hadoop data aggregator),
showing that it achieves good performance while reducing
development effort.