Keepalive

Manage idle and stale connections with TCP and HTTP keepalive.

About keepalive

With keepalive, the kernel sends probe packets with only an acknowledgement flag (ACK) to the TCP or HTTP/2 socket of the destination after the connection was idle for a specific amount of time. This way, the connection does not have to be re-established repeatedly, which could otherwise lead to latency spikes. If the destination returns the packet with an acknowledgement flag (ACK), the connection is determined to be alive. If not, the probe can fail a certain number of times before the connection is considered stale. Agentgateway can then close the stale connection, which can help avoid longer timeouts and retries on broken or stale connections.

Before you begin

1. Set up an agentgateway proxy.
2. Install the httpbin sample app.

TCP keepalive

Keep the TCP connection alive by sending out probes after the connection has been idle for a specific amount of time.

Set up TCP keepalive

1. Create an AgentgatewayPolicy that applies TCP keepalive settings to the httpbin service.

   kubectl apply -f- <<EOF
   apiVersion: agentgateway.dev/v1alpha1
   kind: AgentgatewayPolicy
   metadata:
     name: httpbin-keepalive
     namespace: httpbin
   spec:
     targetRefs:
     - kind: Gateway
       name: agentgateway-proxy
       group: gateway.networking.k8s.io
     frontend:
       tcp:
         keepalive:
           retries: 3
           time: 30s
           interval: 5s
   EOF

   Setting	Description
   retries	The maximum number of keep-alive probes to send without a response before a connection is considered stale.
   time	The number of seconds a connection is idle before the first keep-alive probe is sent.
   interval	The number of seconds between keep-alive probes.

2. Port-forward the gateway proxy on port 15000.

   kubectl port-forward deployment/agentgateway-proxy -n agentgateway-system 15000

3. Get the config dump and verify that the keepalive policy is set as you configured it.

   Example jq command:

   curl -s http://localhost:15000/config_dump | jq '[.policies[] | select(.policy.frontend != null and .policy.frontend.tCP != null and .policy.frontend.tCP.keepalives != null)] | .[0]'

   Example output:

   http://localhost:15000/config_dump

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

   { "key": "frontend/httpbin/httpbin-keepalive:frontend-tcp:httpbin/agentgateway-proxy", "name": { "kind": "AgentgatewayPolicy", "name": "httpbin-keepalive", "namespace": "httpbin" }, "target": { "gateway": { "gatewayName": "agentgateway-proxy", "gatewayNamespace": "httpbin", "listenerName": null } }, "policy": { "frontend": { "tCP": { "keepalives": { "enabled": true, "time": "30s", "interval": "5s", "retries": 3 } } } } }

Cleanup

kubectl delete AgentgatewayPolicy httpbin-keepalive -n httpbin

HTTP keepalive

Keep the HTTP connection alive by sending out probes after the connection has been idle for a specific amount of time.

Set up HTTP keepalive

1. Create an AgentgatewayPolicy that applies HTTP keepalive settings on the agentgateway proxy.

   kubectl apply -f- <<EOF
   apiVersion: agentgateway.dev/v1alpha1
   kind: AgentgatewayPolicy
   metadata:
     name: httpbin-keepalive
     namespace: httpbin
   spec:
     targetRefs:
     - kind: Gateway
       name: agentgateway-proxy
       group: gateway.networking.k8s.io
     frontend:
       http:
         http2KeepaliveInterval: 5s
         http2KeepaliveTimeout: 30s
   EOF

   Setting	Description
   http2KeepaliveInterval	The number of seconds between keep-alive probes.
   http2KeepaliveTimeout	The number of seconds a connection is idle before the first keep-alive probe is sent.

2. Port-forward the gateway proxy on port 15000.

   kubectl port-forward deployment/agentgateway-proxy -n agentgateway-system 15000

3. Get the config dump and verify that the keepalive policy is set as you configured it.

   Example jq command:

   curl -s http://localhost:15000/config_dump | jq '[.policies[] | select(.policy.frontend != null and .policy.frontend.hTTP != null and .policy.frontend.hTTP.http2KeepaliveInterval != null)] | .[0]'

   Example output:

   http://localhost:15000/config_dump

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

   { "key": "frontend/httpbin/httpbin-keepalive:frontend-http:httpbin/agentgateway-proxy", "name": { "kind": "AgentgatewayPolicy", "name": "httpbin-keepalive", "namespace": "httpbin" }, "target": { "gateway": { "gatewayName": "agentgateway-proxy", "gatewayNamespace": "httpbin", "listenerName": null } }, "policy": { "frontend": { "hTTP": { "maxBufferSize": 2097152, "http1MaxHeaders": null, "http1IdleTimeout": "10m0s", "http2WindowSize": null, "http2ConnectionWindowSize": null, "http2FrameSize": null, "http2KeepaliveInterval": "5s", "http2KeepaliveTimeout": "30s" } } } }

Cleanup

kubectl delete AgentgatewayPolicy httpbin-keepalive -n httpbin