Diagnosing Native Errors in .NET Apps Running in the Linux Containers (exit code 139) in AKS

 We might have to sometimes use native assembiles such Aspose.Slides.NET6.CrossPlatform as for specific needs.

 <PackageReference Include="Aspose.Slides.NET6.CrossPlatform" Version="26.9.0" />

However, when there is a native exception which is not propagating the exceptions to .NET app, but fails due to native errors and restart cotianers with exit code 139. 

Exit code 139 in a Linux container means the process was terminated due to a Segmentation Fault (SIGSEGV). The operating system killed the container because it attempted to access a memory location it wasn't allowed to touch. 

Linux calculates this exit code using the formula 128 + Signal Number. Because SIGSEGV is signal 11, the result is: (128+11=139)

Setup Valkey (Open Source Redis) Prerequisites in AKS

 Valkey is the open source redis alternative. We have discussed getting AKS instance ready for Valkey in the post "Create AKS Cluster to Setup Valkey Cluster (Open Source Redis)". Let's look at the prerequisites for setting up Valkey.

First step is setting up a namespace for valkey in the AKS cluster.

# Namespace in aks_vnet for Valkey

---

apiVersion: v1

kind: Namespace

metadata:

  name: valkey

  labels:

    shared-gateway-access: "true"

Identifying VM Sizes Available for AKS in a Given Azure Region

 We sometimes come across issues such as shown below while trying to deploy AKS clusters. It could be due to diffrent reasons. One such case is the below one where there is no availability for the VM size in zone 2 in the region but it has availability in other two regions.

performing CreateOrUpdate: unexpected status 400 (400 Bad Request) with response: {

│   "code": "AvailabilityZoneNotSupported",

│   "details": null,

│   "message": "The zone(s) '2' for resource 'vkdefault' is not supported. The supported zones for location 'eastus2' are '1,3'",

│   "subcode": "",

│   "target": "agentPoolProfile.availabilityZone"

│  }

Get Pod Counts via Kubectl in WSL

 It would be usefull to figure out how many pods running in a given AKS cluster sometimes for various diagnostic needs. In this post let's see how we can use kubectl command to get pod count in diffrent combinations.

Below are some examples.

Create AKS Cluster to Setup Valkey Cluster (Open Source Redis)

 Since bitnami redis images have gone commercial now the best open source redis cluster setup option is to use Valkey, which is guranteed to be open source forever. The source code repos for Valkey is here. We have discussed deploying redis cluster on AKS with bitnami in "Setup Redis Cluster with JSON and Search Modules on AKS with Binami Redis Using Custom Image" However, if we want to deploy Valkey/Redis in cluster in AKS and want to access the Valkey/Redis from outside the AKS cluster, we have to setup AKS networking in a way that each pod is allocated with an IP from the Azure virtual network subnet. In this post let's explore how to setup such an AKS cluster correctly.

Why we need pods in AKS to have IPs from virtual network subnet to deploy Valkey?

When we connect to a Valkey/Redis cluster it always provide diffrent IPs of master nodes to client. Therefore, clients need to acess to IPs of Valkey node pods.

We cannot use Azure CNI overlay for this AKS cluster as it would setup internal network CIDR for pod IPs. Such IPs are not visible outside of AKS. Therefore it is not possible use Azure CNI overlay for AKS clsuter, if we are to deploy Valkey clsuter that should be allowed to access outside of AKS.

We can Azure node subnet mode. But this is not ideal as we have to have a large subnet planned to support boith the node needs as well as pods IP requirement.

The best option is to use Azure CNI Pod Subnet, which would be really useful for this need.

Mount Per Pod Managed Disk to AKS Pod to Provide Isolated Disk Space for Processing Large Files

 In AKS processing files on AKS node disk by application pod is not a recommended approach. It could lead to issues in stability of the AKS node itself. Therefore, we have two options. Either mount an Azure fileshare to the pod as described in "Mount Azure Storage Fileshare Created with Terraform on AKS". The other option is to setup a per pod disk, specially when the need is to process larger files. This option is really useful when we have pods running a single job and when it lives for the lifetime of the job. Example case is use of KEDA scale object with per single message processing from rabbitmq as described in "RabbitMQ KEDA Trigger for AKS Deployed Apps to Scale Out the Apps Accurately".

Expentation is to get a per pod disk attached as shown below.

RabbitMQ KEDA Trigger for AKS Deployed Apps to Scale Out the Apps Accurately

 We have discussed "Setting Up RabbitMQ Cluster in AKS Using RabbitMQ Cluster Operator" in a previous post. Baed on rabbitmq messages we may want to setup a trigger to auto scale our apps to handle the workloads similar to what we have done with eventhubs, azure service bus etc, as described in below posts.

• Setting Up (KEDA) Authentication Trigger for Azure Storage Queue/Service Bus in AKS
• Scale Pods in AKS with Kubernetes Event Driven Autoscaling (KEDA) ScaledJob Based on Azure Service Bus Queue as a Trigger
• Multiple KEDA Triggers for a Scaled Job with Event Hubs in AKS

In this post, let's look at usage of keda scale objects and how we can setup to trigger scaling with rabbit mq messages accurately for AKS deployed apps. The expectation is to scale out apps based on number of messgaes in rabbitmq queues and effective process the the work, while scaling in when there is not much workload on the system.

Depending on above message loads the consumer apps scale out and in accrdingly.

Enable Updating GitHub Environment Variables via GitHub Actions Workflow

 To update environment  variables defined in GitHub environment, via a GitHub action workflow we cannot use the default GITHUB_TOKEN .

✅ GITHUB_TOKEN can interact with repository contents (depending on permissions), create releases, comment on PRs, update issues, etc.

❌ GITHUB_TOKEN cannot update repository environments, environment secrets, or environment variables via the GitHub REST API.