Sometmes it would be necessery to identify which priority classes are used in each pod in a kubernetes environment, specially to plan and reorganize priorities in apps deployed. Let's look at a query to view pods with priority classes using kubectl.
Below command will get all pods in all namespaces with their priority classes name and priority value. The highest priority number value is the highet priority.
We have discussed "Windows AKS Scaled Jobs Handle Graceful Termination for dotnet App using IHostedService When Preemption" previously. However, for Linux scaled jobs we have to handle the graceful termination, using a bash script intead of a PowerShell script.
We can create a script with bash as shown below.
We have discussed "Gracefully Shut Down dotnet 8 IHostedService App - Deployed as a Windows Container in AKS - While Scale In or Pod Deallocations" previously. The approach works fine for pods deployed as a deployment in kubernetes. Similary to the deployment pods, scaled job pod can be terminated abruptly due to preemption in kubernetes, if a high priority pod is scheduled. One way to reolve abrupt termination of scaled job pod due to preemption, would be to assign all scaled jobs to highest possible priority. However, setting highest prority to all scaled jobs is not a good solution, as the job may not require highest priority and job should be able to scheduled after other high priority app pods. Let's look at a better solution that can be implented with pre stop hook for scaled jobs running with base docker image Windows server core 2022.
The pods deployed to AKS gets terminated due to reschduling, low priority evictions as well as during scaled in. We can add a termination grase period and pre stop sleep time as shown below in Linux and Windows containers to allow, sufficient time to ingress services to get updated about terminating pods. However, Windows nanoserver does not support PowerShell. Therefore, we need to use a specific mechanism to pre stop hook for nanoserver images. For nanoserver images shutdown signal is correctly get sent to the dotnet app. So we can just setup a sllep time for pre stop hook as necessary.
Applications implemented with IHostedService in dotnet, deployed to Azure Kubernetes Services (AKS) as containers in pods get terminated when pod recheduling happens or scaling-in opertaions happen. However, unlike Linux containers, the Windows containers does not receive the signal (similar to SIGTERM or SIGINT) to graceful shutdown. Once the pre stop hook is done the container is immediatly killed disregarding the value set in the terminationgraceperiod. Since, the Windows container did not receive a message to start a graceful shut down, and it is killed abruptly, the in flight operations in the Windows app container are abandoned. Such abadoning of operations cause inconsitency in system data and cause system failures. Therefore, it is mandatory to implement a proper graceful shutdown for Windows containers as well. Let's explore the issue in detail and how to implement a proper solution to enable graceful Windows container shut down, for dotent apps implemented with IHostedService. The issue is happening in mcr.microsoft.com/dotnet/runtime:8.0-windowsservercore-ltsc2022 images and the solution is tested with the same.
Windows app pod scaled-in or pod rescedule
Azure Kubernetes Services (AKS) pod restarts can be obtained from the KubePodInventory of the connected log analytics workspace. This data can be depicted in a graph in grafana as described in the post "Pod Restart Counts Grafana Chart with Azure Monitor for AKS". Let's explore how to use same information to create an alert using Grafana to notify when pod restarts are happening in apps in a given kubernetes namespace.
The expectation is to fire alerts from Grafana as shwon below. Note that the alerts can target to send emails, slack notficaition etc. which is not discussed in this post.
kubectl logs command helps us to inspect logs of pods in AKS/kubernetes and useful to diagnose issues. However, when there is too much logs it is harder to read through and find out errors easily. Further, filtering out logs for a given timestamp may be useful at times to identify the issues. In this post let's explore usage of grep with kubectl logs command to filter logs.
Let's take first example to filter for a timestamp in keda operator pod logs. Here -i says to ignore case in logs.
kubectl logs keda-operator-79d756dd66-69gsc -n keda | grep -i '2025-03-04T07:20:24'
Setting up an Azure File Share capacity alert is useful to know when you reach at least 80% of allocated quota for the file share. This will give the teams ample time to increase the allocation to avoid out of space issues. If we are using standard tier for storage account then we need to use one storage account for each file share, to get the correct alert. Sending the alert to slack channel is a useful way to get properly alerted to take action on time. Let's use an example learn how to setup alerts for multiple Azure file shares uing terraform.
Expectation is to get the alerts to slack channel as shown below.
