addressed feedback from elamaran11

Author: freschri

docs/patterns/existing-eks-observability-accelerators/existing-eks-mixed-observability.md

@@ -0,0 +1,78 @@
+# Existing EKS Cluster AWS Mixed Observability Accelerator
+
+## Architecture
+
+The following figure illustrates the architecture of the pattern we will be deploying for Existing EKS Cluster AWS Mixed Observability pattern, using AWS native tools such as CloudWatch and X-Ray and Open Source tools such as Amazon Distro for OpenTelmetry (ADOT) and Prometheus Node Exporter.
+
+![Architecture](../images/mixed-diagram.png)
+
+This example makes use of CloudWatch, as a metric and log aggregation layer, while X-Ray is used as a trace-aggregation layer. In order to collect the metrics and traces, we use the Open Source ADOT collector. Fluent Bit is used to export the logs to CloudWatch Logs.
+
+In this architecture, AWS X-Ray provides a complete view of requests as they travel through your application and filters visual data across payloads, functions, traces, services, and APIs. X-Ray also allows you to perform analytics, to gain powerful insights about your distributed trace data.
+
+Utilizing CloudWatch and X-Ray as an aggregation layer allows for a fully-managed scalable telemetry backend. In this example we get those benefits while still having the flexibility and rapid development of the Open Source collection tools.
+
+## Objective
+
+This pattern aims to add Observability on top of an existing EKS cluster, with a mixture of AWS native and open source managed AWS services.
+
+## Prerequisites:
+
+Ensure that you have installed the following tools on your machine:
+
+1. [aws cli](https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html)
+2. [kubectl](https://Kubernetes.io/docs/tasks/tools/)
+3. [cdk](https://docs.aws.amazon.com/cdk/v2/guide/getting_started.html#getting_started_install)
+4. [npm](https://docs.npmjs.com/cli/v8/commands/npm-install)
+
+You will also need:
+
+1. either an existing EKS cluster, or you can setup a new one with  [Single New EKS Cluster Observability Accelerator](./single-new-eks-cluster.md)
+2. an OpenID Connect (OIDC) provider, associated to the above EKS cluster (note: Single EKS Cluster Pattern takes care of that for you)
+
+## Deploying
+
+1. Edit `~/.cdk.json` by setting the name of your existing cluster:
+
+```json
+    "context": {
+        ...
+        "existing.cluster.name": "...",
+        ...
+    }
+```
+
+2. Edit `~/.cdk.json` by setting the kubectl role name; if you used Single New EKS Cluster Observability Accelerator to setup your cluster, the kubectl role name would be provided by the output of the deployment, on your command-line interface (CLI):
+
+```json
+    "context": {
+        ...
+        "existing.kubectl.rolename":"...",
+        ...
+    }
+```
+
+3. Run the following command from the root of this repository to deploy the pipeline stack:
+
+```bash
+make build
+make pattern existing-eks-mixed-observability deploy
+```
+
+## Verify the resources
+
+Please see [Single New EKS Cluster AWS Mixed Observability Accelerator](./single-new-eks-mixed-observability.md).
+
+## Teardown
+
+You can teardown the whole CDK stack with the following command:
+
+```bash
+make pattern existing-eks-mixed-observability destroy
+```
+
+If you setup your cluster with Single New EKS Cluster Observability Accelerator, you also need to run:
+
+```bash
+make pattern single-new-eks-cluster destroy
+```