updated design images

Signed-off-by: Aswin A <[email protected]>

083-stretch-cluster.md

@@ -1,14 +1,14 @@
 # Stretch Kafka cluster
 
-The Strimzi Kafka operator currently manages Kafka clusters within a single Kubernetes environment. This proposal aims to extend support to stretch Kafka clusters, where brokers and controllers are distributed across multiple Kubernetes clusters.
+The Strimzi Kafka operator currently manages Kafka clusters within a single Kubernetes cluster. This proposal aims to extend support to stretch Kafka clusters, where brokers and controllers of a single Kafka cluster are distributed across multiple Kubernetes clusters.
 
 ## Current situation
 
 At present, the availability of Strimzi-managed Kafka clusters is directly tied to the availability of the underlying Kubernetes cluster. If a Kubernetes cluster experiences an outage, the entire Kafka cluster becomes unavailable, disrupting all connected Kafka clients.
 
 ## Motivation
 
-By distributing Kafka nodes across multiple clusters, a stretch Kafka cluster can tolerate outages of individual Kubernetes clusters and will continue to serve clients seamlessly even if one of the clusters goes down. 
+By evenly distributing Kafka nodes across multiple Kubernetes clusters, a stretch Kafka cluster can tolerate outages of individual Kubernetes clusters, and continue to serve clients seamlessly.
 
 ## Proposal
 
@@ -29,10 +29,10 @@ The cluster operator will be deployed in all Kubernetes clusters and will manage
 This approach will allow users to specify/manage the definition of stretch Kafka cluster in a single location. The operators will then create necessary resources in target Kubernetes clusters, which can then be reconciled/managed by operators on those clusters.
 
 ### Reconciling Kafka and KafkaNodePool resources
-<img width="1321" alt="image" src="https://media.github.ibm.com/user/473362/files/0a1a4e7f-8227-47da-86b1-4b27a83fdb9d">
+![Reconciling Kafka and KafkaNodePool resources](./images/083-reconciling-kafka-knp.png)
 
 ### Reconciling StrimziPodSet resources
-<img width="1317" alt="image" src="https://media.github.ibm.com/user/473362/files/f4524847-3c9c-4a8c-a5fd-4a76b6ec0bf4">
+![Reconciling SPS](./images/083-reconciling-sps.png)
 
 #### KafkaNodePool changes
 A new optional field (`target`) will be introduced in the KafkaNodePool resource specification, to allow users to specify the details of the Kubernetes cluster where the node pool should be deployed. This section will include the target cluster's URL (Kubernetes cluster where resources for this node pool will be created) and the secret containing the kubeconfig data for that cluster. 
@@ -101,7 +101,7 @@ In a stretch Kafka cluster, we'll need bootstrap and broker services to be prese
 #### Cross-cluster communication
 Kafka controllers/brokers are distributed across multiple Kubernetes environments and will need to communicate with each other. Currently, the Strimzi Kafka operator defines Kafka listeners for internal communication (controlplane and replication) between brokers/controllers (Kubernetes services using ports 9090 and 9091). The user is not able to influence how these services are set up and exposed outside the cluster. We would remove this limitation and allow users to define how these internal listeners are configured in the Kafka resource, just like they do for Kafka client listeners.
 
-Users will also be able to override listener configurations in each KafkaNodePool resource, if the listeners need to be exposed in different ways (ingress host names, Ingress annotations etc.) for each Kubernetes cluster. This will be similar to how KafkaNodePools are used to override other configuration like storage etc. To override a listener, KafkaNodePool will define configuration with same listner name as in Kafka resource.
+Users will also be able to override listener configurations in each KafkaNodePool resource, if the listeners need to be exposed in different ways (ingress host names, Ingress annotations etc.) for each Kubernetes cluster. This will be similar to how KafkaNodePools are used to override other configuration like storage etc. To override a listener, KafkaNodePool will define configuration with same listener name as in Kafka resource.
 
 #### Resource cleanup on remote Kubernetes clusters
 As some of the Kubernetes resources will be created on a remote cluster, we will not be able to use standard Kubernetes approaches for deleting resources based on owner references. The operator will need to delete remote resources explicitly when the owning resource is deleted. 
@@ -135,7 +135,7 @@ This proposal only impacts strimzi-kafka-operator project.
 - Use network technologies like skupper, submariner etc to allow internal services to be visible on other clusters
   -  introduces additional dependencies and complexity to the Strimzi project
 
-<img width="1057" alt="image" src="https://media.github.ibm.com/user/473362/files/9a9720f9-9ccf-4d4f-a56c-9a35917af711">
+![Synchronized ClusterOperator](./images/083-synchronized-clusteroperator.png)
 
 
 An alternative approach considered was setting up a stretch Kafka cluster with synchronized `KafkaStretchCluster` and `Kafka` custom resources (CRs). The idea was to introduce a new CR called `KafkaStretchCluster`, which would contain details of all the clusters involved in the stretch Kafka deployment. The spec would include information such as cluster names, secrets for connecting to each Kubernetes cluster, and a list of node pools across the entire stretch cluster.