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gateway

README.md

Gateway

The API Gateway provides an external route into your functions and collects Cloud Native metrics through Prometheus. The gateway also has a UI built-in which can be used to deploy your own functions or functions from the OpenFaaS Function Store then invoke them.

The gateway will scale functions according to demand by altering the service replica count in the Docker Swarm or Kubernetes API. Custom alerts generated by AlertManager are received on the /system/alert endpoint.

In summary:

  • UI built-in
  • Deploy your own functions or from the Function Store
  • Instrumentation via Prometheus
  • Auto-scaling via AlertManager
  • REST API available

Pictured: conceptual architecture when Kubernetes is used as the orchestration provider

Function Providers

Providers for functions can be written using the faas-provider interface in Golang which provides the REST API for interacting with the gateway. The gateway originally interacted with Docker Swarm directly and anything else via a Function Provider - this support was moved into a separate project faas-swarm.

REST API

Swagger docs: https://github.com/openfaas/faas/tree/master/api-docs

Logs

Logs are available at the function level and can be accessed through Swarm or Kubernetes using native tooling. You can also install a Docker logging driver to aggregate your logs. By default functions will not write the request and response bodies to stdout. You can toggle this behaviour by setting read_debug for the request and write_debug for the response.

Tracing

An "X-Call-Id" header is applied to every incoming call through the gateway and is usable for tracing and monitoring calls. We use a UUID for this string.

Header:

X-Call-Id

Within a function this is available as Http_X_Call_Id.

Environmental overrides

The gateway can be configured through the following environment variables:

Option Usage
write_timeout HTTP timeout for writing a response body from your function (in seconds). Default: 8
read_timeout HTTP timeout for reading the payload from the client caller (in seconds). Default: 8
functions_provider_url URL of upstream functions provider - i.e. Swarm, Kubernetes, Nomad etc
faas_nats_address Address of NATS service. Required for asynchronous mode
faas_nats_port Port for NATS service. Requrired for asynchronous mode
faas_prometheus_host Host to connect to Prometheus. Default: "prometheus"
faas_promethus_port Port to connect to Prometheus. Default: 9090
direct_functions true or false - functions are invoked directly over overlay network without passing through provider
direct_functions_suffix Provide a DNS suffix for invoking functions directly over overlay network