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Envoy Proxy is a modern, high performance, small footprint edge and service proxy. Envoy is most comparable to software load balancers such as NGINX and HAProxy. Originally written and deployed at Lyft, Envoy now has a vibrant contributor base and is an official Cloud Native Computing Foundation project.
An API Gateway is a façade that sits between the consumers and producers of an API. Cross-cutting functionality such as authentication, monitoring, and traffic management is implemented in your API Gateway so that your services can remain unaware of these details. In addition, when multiple services are responsible for different APIs (e.g., in a microservices architecture), an API Gateway hides this abstraction detail from the consumer.
There are dozens of different options for API Gateways, depending on your requirements. The Amazon API Gateway is a hosted Gateway that runs in Amazon. Kong is a popular open source API gateway. Or you could build your own on top of a Layer 7 proxy such as Traefik, NGINX, HAProxy, or Envoy. These all have their various strengths and weaknesses.
In general, though, you want to pick an API gateway that can accelerate your development workflow. Traditional API gateways focus on the challenges of API management, so using an API gateway that enables rapid development of services is essential.
Here at Datawire, we've been using Envoy for microservices. Envoy is interesting because, in addition to providing the reverse proxy semantics you need to implement an API Gateway, it also supports the features you need for distributed architectures (in fact, the Istio project builds on Envoy to provide a full-blown services mesh).
So let's take a closer look at deploying Envoy as a full-fledged, self-service API gateway. If you've been following along with our Envoy tutorial so far, we've done the following:
This approach starts to get cumbersome as you add complexity to your deployment. For example, every configuration change requires editing a (complex!) configuration file, and redeploying Envoy. And, we've glossed over the operational aspects of keeping multiple Envoy instances running for scalability and availability.
We thought there would be an easier way, so we wrote Ambassador. Here's what Ambassador does:
Ambassador only deploys in Kubernetes. This means that Ambassador delegates all the hard parts of scaling and availability to Kubernetes. Want to upgrade Ambassador with no downtime? No problem -- just use a Kubernetes rolling update.
We're going to assume that your basic infrastructure is set up enough that you have a Kubernetes cluster running in your cloud environment of choice. For now, we assume that:
kubectlcorrectly talking to a Kubernetes cluster running in EC2 or GKE.
dockerinstalled and working.
That last point is worth a little more discussion. To run something in Kubernetes, we have to be able to pull an Docker image from somewhere that the cluster can reach. When using Minikube, this is no problem, since Minikube runs its own Docker daemon: by definition, anything in the Minikube cluster can talk to that Docker daemon. However, things are different once GKE or EC2 come into play: they can't talk to a Docker daemon on your laptop without heroic measures, so you'll need to explicitly push images somewhere accessible.
Ambassador is deployed as a Kubernetes service. The following configuration will create a service for Ambassador. It also adds a mapping that will route traffic from
/httpbin/ to the public httpbin.org service.
--- apiVersion: v1 kind: Service metadata: labels: service: ambassador name: ambassador annotations: getambassador.io/config: | --- apiVersion: ambassador/v0 kind: Mapping name: httpbin_mapping prefix: /httpbin/ service: httpbin.org:80 host_rewrite: httpbin.org spec: type: LoadBalancer ports: - name: ambassador port: 80 targetPort: 80 selector: service: ambassador
Save the above YAML into a file called
ambassador-service.yaml, and type
kubectl apply -f ambassador-service.yaml to deploy the service.
We have an Ambassador service, but we don't actually have Ambassador running. To do this, we'll need a Kubernetes deployment. If you're using a cluster with RBAC enabled, you'll need to use:
kubectl apply -f https://getambassador.io/yaml/ambassador/ambassador-rbac.yaml
Without RBAC, you can use:
kubectl apply -f https://getambassador.io/yaml/ambassador/ambassador-no-rbac.yaml
Once that's done, you should see three pods for Ambassador:
$ kubectl get pods NAME READY STATUS RESTARTS AGE ambassador-1378270275-51qns 2/2 Running 0 2m ambassador-1378270275-kr361 2/2 Running 0 2m ambassador-1378270275-v10x8 2/2 Running 0 2m $ kubectl get services NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE ambassador 126.96.36.199 a1128c0831f9e... 80/TCP 3m kubernetes 188.8.131.52 <none> 443/TCP 9m
Ambassador relies on Kubernetes for replication, availability, and scaling -- making Ambassador itself very simple. Ambassador also relies on Kubernetes for persistence, so Ambassador has no database.
In order to get access to your microservices through Ambassador, you'll need an external URL to Ambassador's service interface. We'll use
$AMBASSADORURL as shorthand for the base URL of Ambassador.
We'll need to start by getting the external IP address of Ambassador. You can get the IP address by running
kubectl describe service ambassador and looking at the
LoadBalancer Ingress line. (On Minikube, you'll need to use
minikube service --url ambassador.) Set the value of AMBASSADORURL to this address, e.g.,:
In any case, do not include a trailing
$AMBASSADORURL, or the examples in this document won't work.
We can now speak to the
httpbin service using Ambassador:
$ curl $AMBASSADORURL/httpbin/ip/
This will send a request to Ambassador, which then routes the request to the
Under the hood, Ambassador relies on Envoy (and its powerful feature set) for routing, TLS, and the like. Ambassador includes diagnostics that gives more insight into the Envoy configuration that Ambassador is managing. These diagnostics are not publicly exposed by default.
You can access the diagnostics by getting the list of Ambassador pods:
$ kubectl get pods NAME READY STATUS RESTARTS AGE ambassador-1378270275-51qns 2/2 Running 0 2m ambassador-1378270275-kr361 2/2 Running 0 2m ambassador-1378270275-v10x8 2/2 Running 0 2m
forwarding to port 8877 on one of the pods:
kubectl port-forward ambassador-1378270275-51qns 8877
And then visiting http://localhost:8877 in your web browser.
In this article, we've shown how you can deploy Envoy as an API Gateway using Ambassador. Envoy has many powerful features such as sophisticated load balancing algorithms, advanced statistics monitoring, and more. Ambassador exposes many of these features through annotations to support use cases. To learn more, read about Canary deployments or see how to use Prometheus to monitor Envoy and Ambassador.