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README.md

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+# cray-istio Upgrade Notes
+
+## Description
+Cray-Istio is a customized version of the Istio service mesh tailored for HPE's Cray supercomputers and high-performance computing (HPC) workloads. It optimizes Istio's performance to minimize overhead and maximize speed for demanding HPC tasks. Cray-Istio integrates seamlessly with HPE's HPC ecosystem, allowing coordinated management with schedulers and resource managers. It might also include additional security features relevant to HPC environments. This runs after cray-istio-deploy which creates the Istio CRDs that
+are used by this chart (Gateways, VirtualServices, etc.).<br>
+Understanding Cray-Istio builds upon the foundation of Istio, an open-source service mesh. Istio provides features like traffic management, security, and observability for microservices, making it valuable for managing complex HPC deployments.
+
+## Pre-requisites
+- As part of upgrading to a new version, make sure the latest version images are added to artifactory.
+- Helm does not support upgrading CRDs during chart upgrade. They need to be upgraded explicitly which is handled as part of the templates.
+- Make sure to update the latest CRDs in following:
+    - <a href="https://github.com/Cray-HPE/cray-istio/tree/master/kubernetes/cray-istio-operator">cray-istio-operator</a>
+    - <a href="https://github.com/Cray-HPE/cray-istio/tree/master/kubernetes/cray-istio-deploy">cray-istio-deploy</a>
+    - <a href="https://github.com/Cray-HPE/cray-istio/tree/master/kubernetes/cray-istio">cray-istio</a>
+
+## Upgrade
+Once the changes are done, a tag can be pushed so that the helm charts are added to artifactory in stable directory. These charts can be deployed on a cluster using standard loftsman commands after applying the customizations over them.<br>
+
+## STEPS:
+
+### Create sysmgmt.yaml like the following:
+
+```yaml
+apiVersion: manifests/v1beta1
+metadata:
+  name: sysmgmt
+spec:
+  charts:
+  - name: cray-istio-operator
+    source: csm-algol60
+    version: 1.27.0
+    namespace: istio-system
+    timeout: 10m
+  - name: cray-istio-deploy
+    source: csm-algol60
+    version: 1.30.0
+    namespace: istio-system
+    timeout: 10m
+  - name: cray-istio
+    source: csm-algol60
+    version: 2.11.1
+    namespace: istio-system
+    timeout: 20m
+```
+
+### Apply the following command to applying the customizations over them:
+
+```sh
+manifestgen -c customizations.yaml -i sysmgmt.yaml -o sysmgmt-cust.yaml 
+```
+
+### Upgrade the charts using loftsman:
+
+```sh 
+loftsman ship --charts-path <tgz-charts-path> --manifest-path sysmgmt-cust.yaml 
+```
+
+## Contributing
+See the <a href="https://github.com/Cray-HPE/cray-istio/blob/master/CONTRIBUTING.md">CONTRIBUTING.md</a> file for how to contribute to this project.
+
+## License
+This project is copyrighted by Hewlett Packard Enterprise Development LP and is distributed under the MIT license. See the <a href="https://github.com/Cray-HPE/cray-istio/blob/master/LICENSE">LICENSE</a> file for details.