<p>I am deploying a service to <code>Azure Kubernetes Service</code>.</p>
<p>The <code>Horizontal Pod Autoscaler</code> scales the number of pods, whereas the <code>Cluster Autoscaler</code> scales the number of nodes based on the number of pending pods. If my understanding is correct, if I don't set up autoscaling in my deployment file, the <code>HPA</code> won't get triggered, and only one pod will run; therefore, the <code>CA</code> won't get triggered either.</p>
<p>My question is - is there a scenario in <code>AKS</code> where the <code>CA</code> would get triggered, even without setting autoscaling in my deployment file?</p>

user11081980
<blockquote>
<p>My question is - is there a scenario in AKS where the CA would get triggered, even without setting autoscaling in my deployment file?</p>
</blockquote>
<p>Cluster autoscaler is typically used together with the horizontal pod autoscaler. The Horizontal Pod Autoscaler increases or decreases the number of <strong>pods</strong> based on application demand, and the cluster autoscaler adjusts the number of <strong>nodes</strong> as needed to run those additional pods accordingly.</p>
<p>If your deployment does not have the capacity to automatically scale up or down via the <strong>HPA</strong>, <strong>NOR</strong> you don't manually increase number of pods to the level where no additional pods can run due to insufficient resource in your nodes then the <strong>CA</strong> would not be triggered therefore the answer is <strong>NO</strong>.</p>
<p>You might find <a href="https://learn.microsoft.com/en-us/azure/aks/cluster-autoscaler" rel="nofollow noreferrer">this</a> document from official azure docs helpful also.</p>
