Feat: health check probes

app/gateway/traffic-control/health-check-probes.md

@@ -0,0 +1,124 @@
+---
+title: Health check probes
+content_type: reference
+layout: reference
+description: 'Use health check probes to monitor {{site.base_gateaway}} availability.'
+products:
+  - gateway
+breadcrumbs:
+  - /gateway/traffic-control-and-routing/
+works_on:
+  - on-prem
+  - konnect
+tags:
+  - status
+  - monitoring
+  - health
+faqs:
+  - q: What happens if a node is not ready?
+    a: |
+      The `/status/ready` endpoint returns a `503 Service Temporarily Unavailable` response with a `message` field explaining the failure. 
+      This is useful for debugging and monitoring readiness status in real time.
+  - q: What limitations do health check probes have?
+    a: |
+      The health check endpoints do **not** detect:
+      * System performance issues
+      * DNS, cloud, or networking failures
+      * Errors from third-party plugins
+      * Upstream service availability
+related_resources:
+  - text: "Health checks and circuit breakers"
+    url: /gateway/traffic-control/health-checks-circuit-breakers/
+  - text: "Hybrid Mode"
+    url: /gateway/hybrid-mode/
+  - text: Load balancing in {{site.base_gateway}}
+    url: /gateway/load-balancing/
+  - text: Traffic control and routing
+    url: /gateway/traffic-control-and-routing/
+---
+
+The readiness check endpoint has two states: 
+
+* `200 OK`: when {{site.base_gateway}} is ready.
+* `503 Service Temporarily Unavailable`: when {{site.base_gateway}} is not ready. 
+
+The readiness endpoint does not return detailed information about the node status, but it is still useful for load balancers and other tools that need to monitor the readiness of {{site.base_gateway}} instances.
+
+## Enable the node readiness endpoint
+
+To use the [`/status/ready`](/api/gateway/admin-ee/#/operations/get-status) endpoint, enable the status API server in `kong.conf`, and specify the port you want to use. Readiness probes should be enabled on all nodes, including standalone, Control Plane, and Data Plane nodes.
+
+```conf
+status_listen = 0.0.0.0:8100
+```
+
+{:.info}
+> For information on configuring `kong.conf` review the [Managing {{site.base_gateway}} configuration](/gateway/manage-kong-conf/) documentation
+
+## Types of health checks
+
+For each {{site.base_gateway}} node, there are two types of health checks:
+
+* **Liveness**: The `/status` endpoint responds with a `200 OK` status if {{site.base_gateway}} is running. Use:
+
+  ```sh
+  curl -i http://localhost:8100/status
+  ```
+
+* **Readiness**: The `/status/ready` endpoint responds with `200 OK` if {{site.base_gateway}} has a valid config and is ready to serve. Use:
+
+  ```sh
+  curl -i http://localhost:8100/status/ready
+  ```
+
+These endpoints follow the [Kubernetes health check probe patterns](/kubernetes-ingress-controller/service-health-checks/).
+Liveness may return `200 OK` before readiness. Only use readiness probes to determine if a node is ready to receive traffic.
+
+## Readiness by node type
+
+Readiness varies by deployment type. A `200 OK` can mean something different depending on the {{site.base_gateaway}} configuration. 
+
+
+{% navtabs "behaviour" %}
+{% navtab "Traditional mode" %}
+
+In [traditional mode](/gateway/traditional-mode/), readiness returns `200 OK` when:
+
+1. The database is connected
+2. Workers are ready
+3. All plugins are initialized
+
+{% endnavtab %}
+{% navtab "Hybrid mode" %}
+
+In [hybrid mode](/gateway/hybrid-mode/) (`data_plane`) or [DB-less mode](/gateway/db-less-mode/), readiness returns `200 OK` when:
+
+1. A valid, non-empty config is loaded
+2. Workers are ready
+3. All plugins are initialized
+
+{% endnavtab %}
+{% navtab "Hybrid mode (control plane role)" %}
+
+In hybrid mode (`control_plane`), readiness returns `200 OK` when:
+
+1. The database is connected
+
+{% endnavtab %}
+{% endnavtabs %}
+
+
+
+## Kubernetes configuration
+
+Update `readinessProbe` in your deployment:
+
+```yaml
+readinessProbe:
+  httpGet:
+    path: /status/ready
+    port: 8100
+  initialDelaySeconds: 10
+  periodSeconds: 5
+```
+

app/gateway/traffic-control/health-checks-circuit-breakers.md

@@ -27,6 +27,8 @@ related_resources:
   url: /gateway/load-balancing/
 - text: Traffic control and routing
   url: /gateway/traffic-control-and-routing/
+- text: Health check probes
+  url: /gateway/traffic-control/health-checks-probes/
 
 description: |
   {{site.base_gateway}} supports two kinds of health checks, which can be used separately or in conjunction: active and passive (also known as circuit breakers).

tools/track-docs-changes/config/sources.yml

@@ -1181,6 +1181,8 @@ app/gateway/network/dns-config-reference.md:
   - app/_src/gateway/production/networking/dns-considerations.md
 app/gateway/traffic-control/health-checks-circuit-breakers.md:
   - app/_src/gateway/how-kong-works/health-checks.md
+app/gateway/traffic-control/health-check-probes.md:
+  - app/_src/gateway/production/monitoring/healthcheck-probes.md
 app/gateway/traffic-control/load-balancing.md:
   - app/_src/gateway/how-kong-works/load-balancing.md
 app/gateway/traffic-control/blue-green-deployments.md: