@hypertegrity/node-red-contrib-k8s-helper/health-checks.doc.html

Node-RED tools for use in a containerized environment.

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<p>This node offers health checks for flow(s) running in a containerized environment.</p>
When added to a flow, this node will start an HTTP server, listening on the defined port providing three paths: <code>/started</code>, <code>/ready</code> and <code>/alive</code>.<br>
It let's you define <strong>conditions</strong> that must be fulfilled in order to let one or more probes succeed.<br>
<br><div class="infoBoxS">Please note that only one health checks node can be defined within ALL flows and subflows!</div><br>
<h3>Integration</h3>
This node offers three paths: <code>/started</code>, <code>/ready</code> and <code>/alive</code> at a configured port.<br>
These paths can be used as HTTP probes in a containerized environment.<br>
Each of the paths will check for one or more of the defined <strong>conditions</strong> and return a <code>200 OK</code> or <code>500 Internal Error</code> if at least one of the conditions is not fulfilled. Additionally, the body will list the condition(s) that failed.
<p>Read more about kubernetes Probes <a href="https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes">here</a>.</p>
<h3>Example</h3>
Let's think about a flow, subscribing to an MQTT message broker (using an <strong>mqtt in node</strong>).<br>
A <strong>health checks node</strong> will then define a condition, named for example  'MQTT connected' and add this condition to all 3 probes.<br>
A watchdog will check for the <strong>mqtt in node's</strong> status (one of 'connected', 'connecting' or 'disconnected') and its color ("green" if connected) in particular. On a status change (triggered by a <strong>status node</strong>), the health checks node's condition will be set accordingly using a <strong>switch node</strong>: Condition fulfilled if the color is "green", not fulfilled otherwise.<br>
Eventually, the container framework will frequently call the container's HTTP probes and decide what to do, if a check fails.<br>
An appropriate example flow can be found in the Editor (via <strong>Menu->Import->Examples->@hypertegrity/node-red-contrib-k8s-helper</strong>).