Add Documentation for Recommendation

docs/guides/elasticsearch/cli/cli.md

@@ -5,7 +5,7 @@ menu:
     identifier: es-cli-cli
     name: Quickstart
     parent: es-cli-elasticsearch
-    weight: 100
+    weight: 110
 menu_name: docs_{{ .version }}
 section_menu_id: guides
 ---

docs/guides/elasticsearch/recommendation/_index.md

@@ -0,0 +1,10 @@
+---
+title: Elasticsearch Recommendation
+menu:
+  docs_{{ .version }}:
+    identifier: es-recommendation-elasticsearch
+    name: Recommendation
+    parent: es-elasticsearch-guides
+    weight: 100
+menu_name: docs_{{ .version }}
+---

docs/guides/elasticsearch/recommendation/overview.md

@@ -0,0 +1,45 @@
+---
+title: Elasticsearch Recommendation
+description: Elasticsearch Recommendation Overview
+menu:
+  docs_{{ .version }}:
+    identifier: es-recommendation-overview
+    name: Overview
+    parent: es-recommendation-elasticsearch
+    weight: 10
+menu_name: docs_{{ .version }}
+section_menu_id: guides
+---
+
+> New to KubeDB? Please start [here](/docs/README.md).
+
+# Recommendation for KubeDB managed Elasticsearch
+
+Databases on Kubernetes in production grade infrastructure often need to go through several administrative operations depending on specific resource requirements. Such operations include vertical scaling (cpu, memory) and storage expansion. Autoscaling support for KubeDB managed databases takes care of it. However, databases also need to go through some maintenance operations in order to ensure security, enhance performance, getting bug fixes and new features etc. Such operations mostly require organization's manual intervention. Even if these operations are automated, they need to be done in surveillance. KubeDB simplifies this by generating K8s Native Recommendations. 
+
+## Overview
+
+Recommendation is a custom resource definition object which is created by KubeDB ops-manager controller and managed by supervisor. So, You need to have KubeDB and Supervisor installed first. You can simply install supervisor along with other KubeDB components using `--set supervisor.enabled=true` flag while installing KubeDB via helm chart.
+
+<p align="center">
+<img alt="Recommendation Generation"  src="/docs/guides/elasticsearch/recommendation/images/recommendation-generation.png">
+</p>
+
+KubeDB provisioner watches user provided database custom resource spec and creates/sync all the necessary DB resources. Once the Database is ready KubeDB Ops-manager watches the DB and creates Recommendation if it requires. KubeDB Supervisor then watches the Recommendation, updates status of the recommendation, creates recommended operation via OpsRequest if deadline reaches or manually triggered and watches the OpsRequest status to update accordingly in Recommendation custom resource.
+
+KubeDB provides Three types of recommendation for Elasticsearch and Opensearch.
+
+1. [Version Update Recommendation](./version-update-recommendation.md)
+2. TLS Certificate Rotation Recommendation
+3. Authentication Secret Rotation Recommendation
+
+The next page describes these recommendations, how to enable/disable them, their generation mechanism and usability.
+
+## Next Steps
+
+- Learn how to monitor Elasticsearch database with KubeDB using [builtin-Prometheus](/docs/guides/elasticsearch/monitoring/using-builtin-prometheus.md) and using [Prometheus operator](/docs/guides/elasticsearch/monitoring/using-prometheus-operator.md).
+- Learn how to monitor PostgreSQL database with KubeDB using [builtin-Prometheus](/docs/guides/postgres/monitoring/using-builtin-prometheus.md) and using [Prometheus operator](/docs/guides/postgres/monitoring/using-prometheus-operator.md).
+- Learn how to monitor MySQL database with KubeDB using [builtin-Prometheus](/docs/guides/mysql/monitoring/builtin-prometheus/index.md) and using [Prometheus operator](/docs/guides/mysql/monitoring/prometheus-operator/index.md).
+- Learn how to monitor MongoDB database with KubeDB using [builtin-Prometheus](/docs/guides/mongodb/monitoring/using-builtin-prometheus.md) and using [Prometheus operator](/docs/guides/mongodb/monitoring/using-prometheus-operator.md).
+- Learn how to monitor Redis server with KubeDB using [builtin-Prometheus](/docs/guides/redis/monitoring/using-builtin-prometheus.md) and using [Prometheus operator](/docs/guides/redis/monitoring/using-prometheus-operator.md).
+- Learn how to monitor Memcached server with KubeDB using [builtin-Prometheus](/docs/guides/memcached/monitoring/using-builtin-prometheus.md) and using [Prometheus operator](/docs/guides/memcached/monitoring/using-prometheus-operator.md).

docs/guides/elasticsearch/recommendation/version-update-recommendation.md

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+---
+title: Elasticsearch Version Update Recommendation
+menu:
+  docs_{{ .version }}:
+    identifier: es-version-update-recommendation
+    name: Version Update Recommendation
+    parent: es-recommendation-elasticsearch
+    weight: 20
+menu_name: docs_{{ .version }}
+section_menu_id: guides
+---
+
+> New to KubeDB? Please start [here](/docs/README.md).
+
+# Elasticsearch Version Update Recommendation
+
+Database versions often need to be updated due to several reasons. Older database versions may have vulnerabilities that hackers can exploit. New versions often include optimizations for query execution, indexing, and storage mechanisms. Modern databases frequently introduce new features, such as better data types, improved indexing methods, or advanced analytics capabilities. Database vendors release patches and updates to address these issues and introduce new features.
+
+`Recommendation` is a Kubernetes `Custom Resource Definitions` (CRD). It provides a declarative recommendation for KubeDB managed databases like [Elasticsearch](https://www.elastic.co/products/elasticsearch) and [OpenSearch](https://opensearch.org/) in a Kubernetes native way. KubeDB generates Elasticsearch/Opensearch Version Update recommendation regarding three particular cases. 
+
+1. There's been an update in the current version image
+2. There's a new version available with a minor/patch fix.
+3. There's a new major version available
+
+Let's go through a demo to see version update recommendations being generated. First, get the available Elasticsearch versions provided by KubeDB.
+
+```bash
+$ kubectl get elasticsearchversions | grep xpack
+xpack-6.8.23        6.8.23    ElasticStack   ghcr.io/appscode-images/elastic:6.8.23                        17h
+xpack-7.13.4        7.13.4    ElasticStack   ghcr.io/appscode-images/elastic:7.13.4                        17h
+xpack-7.14.2        7.14.2    ElasticStack   ghcr.io/appscode-images/elastic:7.14.2                        17h
+xpack-7.16.3        7.16.3    ElasticStack   ghcr.io/appscode-images/elastic:7.16.3                        17h
+xpack-7.17.15       7.17.15   ElasticStack   ghcr.io/appscode-images/elastic:7.17.15                       17h
+xpack-7.17.23       7.17.23   ElasticStack   ghcr.io/appscode-images/elastic:7.17.23                       17h
+xpack-7.17.25       7.17.25   ElasticStack   ghcr.io/appscode-images/elastic:7.17.25                       16h
+xpack-8.11.1        8.11.1    ElasticStack   ghcr.io/appscode-images/elastic:8.11.1                        17h
+xpack-8.11.4        8.11.4    ElasticStack   ghcr.io/appscode-images/elastic:8.11.4                        17h
+xpack-8.13.4        8.13.4    ElasticStack   ghcr.io/appscode-images/elastic:8.13.4                        17h
+xpack-8.14.1        8.14.1    ElasticStack   ghcr.io/appscode-images/elastic:8.14.1                        17h
+xpack-8.14.3        8.14.3    ElasticStack   ghcr.io/appscode-images/elastic:8.14.3                        17h
+xpack-8.15.0        8.15.0    ElasticStack   ghcr.io/appscode-images/elastic:8.15.0                        17h
+xpack-8.15.4        8.15.4    ElasticStack   ghcr.io/appscode-images/elastic:8.15.4                        16h
+xpack-8.16.0        8.16.0    ElasticStack   ghcr.io/appscode-images/elastic:8.16.0                        16h
+xpack-8.2.3         8.2.3     ElasticStack   ghcr.io/appscode-images/elastic:8.2.3                         17h
+xpack-8.5.3         8.5.3     ElasticStack   ghcr.io/appscode-images/elastic:8.5.3                         17h
+xpack-8.6.2         8.6.2     ElasticStack   ghcr.io/appscode-images/elastic:8.6.2                         17h
+xpack-8.8.2         8.8.2     ElasticStack   ghcr.io/appscode-images/elastic:8.8.2                         17h
+```
+
+Let's deploy an Elasticsearch cluster with version `xpack-8.15.0`.
+
+```yaml
+apiVersion: kubedb.com/v1
+kind: Elasticsearch
+metadata:
+  name: es
+  namespace: demo
+spec:
+  version: xpack-8.15.0
+  storageType: Durable
+  deletionPolicy: WipeOut
+  topology:
+    master:
+      replicas: 2
+      storage:
+        storageClassName: "standard"
+        accessModes:
+        - ReadWriteOnce
+        resources:
+          requests:
+            storage: 1Gi
+    data:
+      replicas: 2
+      storage:
+        storageClassName: "standard"
+        accessModes:
+        - ReadWriteOnce
+        resources:
+          requests:
+            storage: 1Gi
+    ingest:
+      replicas: 1
+      storage:
+        storageClassName: "standard"
+        accessModes:
+        - ReadWriteOnce
+        resources:
+          requests:
+            storage: 1Gi
+```
+
+
+
+## Next Steps
+
+- Learn about [backup & restore](/docs/guides/elasticsearch/backup/stash/overview/index.md) Elasticsearch database using Stash.
+- Learn how to configure [Elasticsearch Topology Cluster](/docs/guides/elasticsearch/clustering/topology-cluster/simple-dedicated-cluster/index.md).
+- Monitor your Elasticsearch database with KubeDB using [`out-of-the-box` Prometheus operator](/docs/guides/elasticsearch/monitoring/using-prometheus-operator.md).
+- Use [private Docker registry](/docs/guides/elasticsearch/private-registry/using-private-registry.md) to deploy Elasticsearch with KubeDB.
+- Want to hack on KubeDB? Check our [contribution guidelines](/docs/CONTRIBUTING.md).