Request Buffering

The Envoy buffer filter is used to stop filter iteration and wait for a fully buffered complete request. This is useful in different situations including protecting some applications from having to deal with partial requests and high network latency.

Enabling request buffering requires specifying a size limit for the buffer. Any requests that are larger than the limit will stop the buffering and return a HTTP 413 Content Too Large response.

Envoy Gateway introduces a new CRD called BackendTrafficPolicy that allows the user to enable request buffering. This instantiated resource can be linked to a Gateway, or HTTPRoute.

If the target of the BackendTrafficPolicy is a Gateway, the request buffering will be applied to all xRoutes under that Gateway.

Prerequisites

Follow the steps below to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.

Configuration

Enable request buffering by creating an BackendTrafficPolicy and attaching it to the example HTTPRoute.

HTTPRoute

• Apply from stdin
• Apply from file

cat <<EOF | kubectl apply -f -
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: BackendTrafficPolicy
metadata:
  name: request-buffer
spec:
  targetRefs:
  - group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: foo
  requestBuffer:
    limit: 4 # Supports SI units e.g. 4Ki, 1Mi
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: foo
spec:
  parentRefs:
  - name: eg
  hostnames:
  - "www.example.com"
  rules:
  - backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000
      weight: 1
    matches:
    - path:
        type: PathPrefix
        value: /foo
EOF

---
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: BackendTrafficPolicy
metadata:
  name: request-buffer
spec:
  targetRefs:
  - group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: foo
  requestBuffer:
    limit: 4 # Supports SI units e.g. 4Ki, 1Mi
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: foo
spec:
  parentRefs:
  - name: eg
  hostnames:
  - "www.example.com"
  rules:
  - backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000
      weight: 1
    matches:
    - path:
        type: PathPrefix
        value: /foo

A HTTPRoute resource is created for the /foo path prefix. The request-buffer BackendTrafficPolicy has been created and targeted HTTPRoute foo to enable request buffering. A small buffer limit of 4 bytes is purposely chosen to make testing easier.

Verify the HTTPRoute configuration and status:

kubectl get httproute/foo -o yaml

Verify the BackendTrafficPolicy configuration:

kubectl get backendtrafficpolicy/request-buffer -o yaml

Testing

Ensure the GATEWAY_HOST environment variable from the Quickstart is set. If not, follow the Quickstart instructions to set the variable.

echo $GATEWAY_HOST

HTTPRoute

We will try sending a request with an empty json object that is less than the buffer limit of 4 bytes

curl -H "Host: www.example.com" "http://${GATEWAY_HOST}/foo" -XPOST -d '{}'

We will see the following output. The Content-Length header will be added by the buffer filter.

{
 "path": "/foo",
 "host": "www.example.com",
 "method": "POST",
 "proto": "HTTP/1.1",
 "headers": {
  "Accept": [
   "*/*"
  ],
  "Content-Length": [
   "2"
  ],
  "Content-Type": [
   "application/x-www-form-urlencoded"
  ],
  "User-Agent": [
   "curl/8.7.1"
  ],
  "X-Envoy-External-Address": [
   "127.0.0.1"
  ],
  "X-Forwarded-For": [
   "10.244.0.2"
  ],
  "X-Forwarded-Proto": [
   "http"
  ],
  "X-Request-Id": [
   "daf7067e-a9e5-48da-86d2-6f5d9ccfb57e"
  ]
 },
 "namespace": "default",
 "ingress": "",
 "service": "",
 "pod": "backend-869c8646c5-9vm4l"
}

Next we will try sending a json object that is larger than 4 bytes. We will also write the status code to make it clear.

curl -H "Host: www.example.com" "http://${GATEWAY_HOST}/foo" -XPOST -d '{"key": "value"}' -w "\nStatus Code: %{http_code}"

We will now see that sending a payload of {"key": "value"} which is larger than the request buffer limit of 4 bytes returns a HTTP 413 Payload Too Large response

Payload Too Large
Status Code: 413

Clean-Up

Follow the steps from the Quickstart to uninstall Envoy Gateway and the example manifest.

Delete the BackendTrafficPolicy and HTTPRoute:

kubectl delete httproute/foo
kubectl delete backendtrafficpolicy/request-buffer