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<div id="app" data-server-rendered="true"><div class="theme-container"><header class="navbar"><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/" class="home-link router-link-active"><img src="/img/fairwinds-logo.svg" alt="Fairwinds Polaris Documentation" class="logo"> <span class="site-name can-hide">Fairwinds Polaris Documentation</span></a> <div class="links"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="https://github.com/FairwindsOps/polaris" target="_blank" rel="noopener noreferrer" class="nav-link external">
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<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div> <!----></nav></div></header> <div class="sidebar-mask"></div> <aside class="sidebar"><nav class="nav-links"><div class="nav-item"><a href="https://github.com/FairwindsOps/polaris" target="_blank" rel="noopener noreferrer" class="nav-link external">
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<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div> <!----></nav> <ul class="sidebar-links"><li><section class="sidebar-group depth-0"><a href="/" class="sidebar-heading clickable router-link-active"><span>Polaris</span> <!----></a> <ul class="sidebar-links sidebar-group-items"><li><a href="/changelog/" class="sidebar-link">Changelog</a></li><li><a href="/code-of-conduct/" class="sidebar-link">Code of Conduct</a></li><li><a href="/contributing/" class="sidebar-link">Contributing</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>Ways to Run Polaris</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/dashboard/" class="sidebar-link">Dashboard</a></li><li><a href="/admission-controller/" class="sidebar-link">Admission Controller</a></li><li><a href="/infrastructure-as-code/" class="sidebar-link">Infrastructure as Code</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>Customization</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/customization/configuration/" class="sidebar-link">Configuration</a></li><li><a href="/customization/checks/" class="sidebar-link">Check Settings</a></li><li><a href="/customization/custom-checks/" class="sidebar-link">Custom Checks</a></li><li><a href="/customization/exemptions/" class="sidebar-link">Exemptions</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading open"><span>Checks</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/checks/security/" class="sidebar-link">Security</a></li><li><a href="/checks/efficiency/" class="sidebar-link">Efficiency</a></li><li><a href="/checks/reliability/" aria-current="page" class="active sidebar-link">Reliability</a></li></ul></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="reliability"><a href="#reliability" class="header-anchor">#</a> Reliability</h1> <p>These checks help to make sure your workloads are always available,
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and are running the correct image.</p> <table><thead><tr><th>key</th> <th>default</th> <th>description</th></tr></thead> <tbody><tr><td><code>reliability.readinessProbeMissing</code></td> <td><code>warning</code></td> <td>Fails when a readiness probe is not configured for a pod.</td></tr> <tr><td><code>reliability.livenessProbeMissing</code></td> <td><code>warning</code></td> <td>Fails when a liveness probe is not configured for a pod.</td></tr> <tr><td><code>reliability.tagNotSpecified</code></td> <td><code>danger</code></td> <td>Fails when an image tag is either not specified or <code>latest</code>.</td></tr> <tr><td><code>reliability.pullPolicyNotAlways</code></td> <td><code>warning</code></td> <td>Fails when an image pull policy is not <code>always</code>.</td></tr> <tr><td><code>reliability.priorityClassNotSet</code></td> <td><code>ignore</code></td> <td>Fails when a priorityClassName is not set for a pod.</td></tr> <tr><td><code>reliability.multipleReplicasForDeployment</code></td> <td><code>ignore</code></td> <td>Fails when there is only one replica for a deployment.</td></tr></tbody></table> <h2 id="background"><a href="#background" class="header-anchor">#</a> Background</h2> <p>Readiness and liveness probes can help maintain the health of applications running inside Kubernetes. By default, Kubernetes only knows whether or not a process is running, not if it's healthy. Properly configured readiness and liveness probes will also be able to ensure the health of an application.</p> <p>Readiness probes are designed to ensure that an application has reached a "ready" state. In many cases there is a period of time between when a webserver process starts and when it is ready to receive traffic. A readiness probe can ensure the traffic is not sent to a pod until it is actually ready to receive traffic.</p> <p>Liveness probes are designed to ensure that an application stays in a healthy state. When a liveness probe fails, the pod will be restarted.</p> <p>Docker's <code>latest</code> tag is applied by default to images where a tag hasn't been specified. Not specifying a specific version of an image can lead to a wide variety of problems. The underlying image could include unexpected breaking changes that break your application whenever the latest image is pulled. Reusing the same tag for multiple versions of an image can lead to different nodes in the same cluster having different versions of an image, even if the tag is identical.</p> <p>Related to that, relying on cached versions of a Docker image can become a security vulnerability. By default, an image will be pulled if it isn't already cached on the node attempting to run it. This can result in variations in images that are running per node, or potentially provide a way to gain access to an image without having direct access to the ImagePullSecret. With that in mind, it's often better to ensure the a pod has <code>pullPolicy: Always</code> specified, so images are always pulled directly from their source.</p> <h2 id="further-reading"><a href="#further-reading" class="header-anchor">#</a> Further Reading</h2> <ul><li><a href="https://vsupalov.com/docker-latest-tag/" target="_blank" rel="noopener noreferrer">What's Wrong With The Docker :latest Tag?<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li> <li><a href="https://medium.com/@trstringer/kubernetes-alwayspullimages-admission-control-the-importance-implementation-and-security-d83ff3815840" target="_blank" rel="noopener noreferrer">Kubernetes’ AlwaysPullImages Admission Control — the Importance, Implementation, and Security Vulnerability in its Absence<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li> <li><a href="https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-probes/" target="_blank" rel="noopener noreferrer">Kubernetes Docs: Configure Liveness and Readiness Probes<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li> <li><a href="https://medium.com/spire-labs/utilizing-kubernetes-liveness-and-readiness-probes-to-automatically-recover-from-failure-2fe0314f2b2e" target="_blank" rel="noopener noreferrer">Utilizing Kubernetes Liveness and Readiness Probes to Automatically Recover From Failure<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li> <li><a href="https://blog.colinbreck.com/kubernetes-liveness-and-readiness-probes-how-to-avoid-shooting-yourself-in-the-foot/" target="_blank" rel="noopener noreferrer">Kubernetes Liveness and Readiness Probes: How to Avoid Shooting Yourself in the Foot<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></div> <footer class="page-edit"><div class="edit-link"><a href="https://github.com/FairwindsOps/polaris/edit/master/docs-md/checks/reliability.md" target="_blank" rel="noopener noreferrer">Help us improve this page</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----></footer> <div class="page-nav"><p class="inner"><span class="prev">
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