Listener connection

Configure connection settings between downstream services and a gateway listener.

You can configure the following listener connection settings:

• Change the number of bytes for the read/write buffer
• Configure TCP keepalive

If an upstream service is unavailable, the service is removed from the load balancing pool until health is re-established.

For more information, see the following resources.

• Gloo Mesh Gateway API docs

About

Learn more about the listener connection settings that you can modify.

About read and write buffer limits

By default, Gloo Gateway is set up with 1MiB of request read and write buffer for each gateway listener. For large requests that must be buffered and that exceed the default buffer limit, Gloo Gateway either disconnects the connection to the downstream service if headers were already sent, or returns a 500 HTTP response code. To make sure that large requests can be sent and received, you can specify the maximum number of bytes that you want to allow to be buffered between the gateway and the downstream service.

About TCP keepalive settings for downstream apps

Configure TCP keepalive for downstream services to keep a connection to the gateway open during long idle periods. A typical use case for this setting is deploying an AWS NLB instance in front of Gloo Gateway. The AWS NLB has an idle timeout of 350 seconds that cannot be changed. Without TCP keepalive, the connection from the gateway to the AWS NLB silently closes after 350 seconds of idle time. However, the connection from the client to the AWS NLB remains intact. When the client sends a request to the AWS NLB, the request cannot be forwarded to the gateway anymore and the NLB returns a reset packet (RST). Because the client cannot interpret the RST packet, the connection to the AWS NLB is closed.

To make sure that the connection from the AWS NLB to the gateway remains open, even during long idle periods, you can configure TCP keepalive for a listener.

For more information, see the following resources.

• Gloo listener connection policy API docs

Before you begin

1. Set up Gloo Mesh Gateway in a single cluster.
2. Install Bookinfo and other sample apps.

3. Configure an HTTP listener on your gateway and set up basic routing for the sample apps.

Configure listener connection policies

You can apply a connection policy at the gateway listener level. For more information, see Applying policies.

apiVersion: resilience.policy.gloo.solo.io/v2
kind: ListenerConnectionPolicy
metadata:
  name: listener-connection
  namespace: httpbin
spec:
  applyToListeners:
  - virtualGateway:
      name: istio-ingressgateway
      namespace: bookinfo
      cluster: $CLUSTER_NAME
    port:
      number: 80
  config:
    perConnectionBufferLimitBytes: 16384

apiVersion: resilience.policy.gloo.solo.io/v2
kind: ListenerConnectionPolicy
metadata:
  name: http-buffer
  namespace: bookinfo
spec:
  applyToListeners:
  - port:
      number: 443
    virtualGateway:
      cluster: cluster-1
      name: istio-ingressgateway
      namespace: bookinfo
  config:
    tcpKeepalive:
      interval: 1m
      probes: 5
      time: 240s

Verify listener connection policies

Verify that the listener connection settings are updated in the Envoy filter.

1. Apply the listener connection policy in your cluster.

   kubectl apply -f- <<EOF 
   apiVersion: resilience.policy.gloo.solo.io/v2
   kind: ListenerConnectionPolicy
   metadata:
     name: listener-connection
     namespace: bookinfo
   spec:
     config:
       perConnectionBufferLimitBytes: 16384
       tcpKeepalive:
         interval: 1m
         probes: 5
         time: 240s
     applyToListeners:
     - virtualGateway:
         name: istio-ingressgateway
         namespace: bookinfo
         cluster: $CLUSTER_NAME
       port:
         number: 80
   EOF

2. Check that the configuration is applied in the Envoy filter.

   kubectl get envoyfilter istio-ingressgateway-listener-8080-listener-connection -n istio-ingress -o yaml

   Example output:

   apiVersion: networking.istio.io/v1alpha3
   kind: EnvoyFilter
   metadata:
     creationTimestamp: "2023-06-05T18:05:26Z"
     generation: 1
     labels:
       context.mesh.gloo.solo.io/cluster: gloo-gateway-docs-mgt
       context.mesh.gloo.solo.io/namespace: istio-ingress
       context.mesh.gloo.solo.io/workspace: gloo-gateway-docs-mgt
       gloo.solo.io/parent_cluster: gloo-gateway-docs-mgt
       gloo.solo.io/parent_group: networking.gloo.solo.io
       gloo.solo.io/parent_kind: VirtualGateway
       gloo.solo.io/parent_name: istio-ingressgateway
       gloo.solo.io/parent_namespace: bookinfo
       gloo.solo.io/parent_version: v2
       reconciler.mesh.gloo.solo.io/name: translator
     name: istio-ingressgateway-listener-8080-listener-connection
     namespace: istio-ingress
     resourceVersion: "18104008"
     uid: 962d88bf-7373-45f9-98bc-510de612d3ec
   spec:
     configPatches:
     - applyTo: LISTENER
       match:
         listener:
           portNumber: 8080
       patch:
         operation: MERGE
         value:
           per_connection_buffer_limit_bytes: 16384
     - applyTo: LISTENER
       match:
         listener:
           portNumber: 8080
       patch:
         operation: MERGE
         value:
           socket_options:
           - description: enable keep-alive
             int_value: 1
             level: 1
             name: 9
             state: STATE_PREBIND
           - description: idle time before first keep-alive probe is sent
             int_value: 240
             level: 6
             name: 4
             state: STATE_PREBIND
           - description: keep-alive interval
             int_value: 60
             level: 6
             name: 5
             state: STATE_PREBIND
           - description: keep-alive probes count
             int_value: 5
             level: 6
             name: 6
             state: STATE_PREBIND
     workloadSelector:
       labels:
         istio: ingressgateway

Cleanup

kubectl delete listenerconnectionpolicy listener-connection -n bookinfo