Slim and Fast: Low-Overhead Container Overlay Network With Fast Connection Setup

Large-scale cloud applications today are often deployed using multiple containers, and a container overlay network is the de facto method to provide connectivity among these containers. However, the existing tunneling-based overlay network incurs significant performance overhead due to the need of transformation for every packet. Recent work Slim, through manipulating connection-level meta-data, allows containers to use host OS sockets directly thus they can achieve good performance without extra packet tunneling. Nevertheless, the connection setup is significantly slowed down, which requires an extra round-trip communication between both sides to pass the mapping information of the host OS socket and the container socket. This greatly hurts the performance of many cloud applications that must process short connections at high speed. We propose SlimFast, a low-overhead container overlay network which provides a fast connection setup. SlimFast directly uses the host OS socket for container communication as Slim. However, SlimFast needs no extra communication during connection setup. We reserve a dedicated host port for the container network and use socket mapping table to locally find the right container socket during connection setup. We implement SlimFast which is compatible with existing container applications. Experiments show that, SlimFast can improve the connection setup time by about 2.1x compared with Slim, meanwhile maintaining low-overhead during data transmission as Slim. This brings significant performance improvement to real applications. Particularly, testbed results show that SlimFast improves the throughput of Nginx proxy and Memcached by about 0.9x and 2.2x, respectively.