Advanced Setup

In this guide you will learn how to setup fission in order to serve heavy workloads on production systems.

Define correct resource request/limits

By default, there is no resource requests/limits setting for fission component pods. But it’s always wise set them up if you’re trying to running any application on Kubernetes for production. We recommend that you run benchmarks to simulate real traffic and setup resource request/limits of components accordingly.

You can get component pods resource usage by using the following command.

$ kubectl -n fission top pod

And follow the guide to setup components’ deployment.

Create HPA for router

NOTE: You have to set up resource requests/limits for router before creating HPA.

The router is the entry point of all functions. It accepts, verifies and redirects requests to corresponding function pods. As workload goes higher, router consumes more resources than idle state and users may experience higher latency. To prevent this, you have to scale the replicas of router based on your use case. However, in real world cases, the workload goes up and down in different time slot and it’s not realistic to give a fixed number of replicas

Horizontal Pod Autoscaler a.k.a HPA is the way for Kubernetes to scale the replicas of a deployment based on the overall resource utilization across pods. Once HPA created, Kubernetes will then scale in/out the replicas of router automatically.

Visit HPA documentation to know how to setup HPA for router deployment.

Enable Keep-Alive setting in router

NOTE: Require 1.4.0+

Keep-Alive allows to use existing connections to send requests without creating a new one and lower the latency for subsequent requests. However, it also limits the ability to distribute traffic to new pods since existing connections remain connected to old pods

Keep-Alive

As shown in the figure above, the router tries to send requests to v1 function pod even after v2 is up. Only when the v1 function pod is terminated, router will then re-establish connections to v2. (See issue here)

You can enable Keep-Alive by setting environment variable as follows at router deployment.

env:
- name: ROUTER_ROUND_TRIP_DISABLE_KEEP_ALIVE
  value: "false"

Couple things worth noticing:

  1. This setting increases time for router(s) to switch to newer version for functions that use newdeploy as executor type. You can prevent this by setting short grace period (--graceperiod) when creating environment.
  2. There is an increase in memory consumption of router to keep all active connections.

Setup SSL/TLS for functions

Since fission router is not responsible to handle the encrypted traffic to functions, you should put fission routers behind any existing proxy solution like NGINX, Caddy or Ambassador that helps to handle SSL/TLS connections.

Client --- SSL/TLS ---> Proxy ------> Router ------> Function  

Also, you can configure proxy upstream setting to avoid exposing the real URL route path of fission function to router to the public network.

Client --- /bar ---> Proxy --- /foo/bar ---> Router