Add SQL Server Arbiter Node Guide

Signed-off-by: Neaj Morshad <[email protected]>

docs/guides/mariadb/scaling/vertical-scaling/cluster/index.md

@@ -99,7 +99,7 @@ $ kubectl get pod -n demo sample-mariadb-0 -o json | jq '.spec.containers[].reso
 }
 ```
 
-You can see the Pod has the default resources which is assigned by Kubedb operator.
+You can see the Pod has the default resources which is assigned by KubeDB operator.
 
 We are now ready to apply the `MariaDBOpsRequest` CR to update the resources of this database.
 

docs/guides/mongodb/concepts/mongodb.md

@@ -524,7 +524,7 @@ The `spec.podTemplate.spec.containers[].name` field used to specify the name of
 
 Note that, KubeDB does not allow `MONGO_INITDB_ROOT_USERNAME` and `MONGO_INITDB_ROOT_PASSWORD` environment variables to set in `spec.podTemplate.spec.env`. If you want to use custom superuser and password, please use `spec.authSecret` instead described earlier.
 
-If you try to set `MONGO_INITDB_ROOT_USERNAME` or `MONGO_INITDB_ROOT_PASSWORD` environment variable in MongoDB crd, Kubedb operator will reject the request with following error,
+If you try to set `MONGO_INITDB_ROOT_USERNAME` or `MONGO_INITDB_ROOT_PASSWORD` environment variable in MongoDB crd, KubeDB operator will reject the request with following error,
 
 ```ini
 Error from server (Forbidden): error when creating "./mongodb.yaml": admission webhook "mongodb.validators.kubedb.com" denied the request: environment variable MONGO_INITDB_ROOT_USERNAME is forbidden to use in MongoDB spec

docs/guides/mongodb/scaling/vertical-scaling/replicaset.md

@@ -101,7 +101,7 @@ $ kubectl get pod -n demo mg-replicaset-0 -o json | jq '.spec.containers[].resou
 }
 ```
 
-You can see the Pod has the default resources which is assigned by Kubedb operator.
+You can see the Pod has the default resources which is assigned by KubeDB operator.
 
 We are now ready to apply the `MongoDBOpsRequest` CR to update the resources of this database.
 

docs/guides/mongodb/scaling/vertical-scaling/sharding.md

@@ -132,7 +132,7 @@ $ kubectl get pod -n demo mg-sharding-shard0-0 -o json | jq '.spec.containers[].
 }
 ```
 
-You can see all the Pod of mongos, configserver and shard has default resources which is assigned by Kubedb operator.
+You can see all the Pod of mongos, configserver and shard has default resources which is assigned by KubeDB operator.
 
 We are now ready to apply the `MongoDBOpsRequest` CR to update the resources of mongos, configserver and shard nodes of this database.
 

docs/guides/mongodb/scaling/vertical-scaling/standalone.md

@@ -97,7 +97,7 @@ $ kubectl get pod -n demo mg-standalone-0 -o json | jq '.spec.containers[].resou
 }
 ```
 
-You can see the Pod has default resources which is assigned by the Kubedb operator.
+You can see the Pod has default resources which is assigned by the KubeDB operator.
 
 We are now ready to apply the `MongoDBOpsRequest` CR to update the resources of this database.
 

docs/guides/mssqlserver/clustering/arbiter.md

@@ -0,0 +1,146 @@
+---
+title: Arbiter Node for MS SQL Server Cluster with Even Nodes
+menu:
+  docs_{{ .version }}:
+    identifier: arbiter-guides
+    name: Arbiter Node for AG Cluster 
+    parent: ms-arbiter
+    weight: 15
+menu_name: docs_{{ .version }}
+section_menu_id: guides
+---
+
+> New to KubeDB? Please start [here](/docs/README.md).
+
+# Arbiter Node for Microsoft SQL Server Cluster with Even Nodes
+
+Here we will show how to use KubeDB to provision a SQL Server even-sized Availability Group Cluster with Arbiter Node.
+
+## Before You Begin
+
+- You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using [kind](https://kind.sigs.k8s.io/docs/user/quick-start/).
+
+- Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps [here](/docs/setup/README.md). Make sure install with helm command including `--set global.featureGates.MSSQLServer=true` to ensure MSSQLServer CRD installation.
+
+- To configure TLS/SSL in `MSSQLServer`, `KubeDB` uses `cert-manager` to issue certificates. So first you have to make sure that the cluster has `cert-manager` installed. To install `cert-manager` in your cluster following steps [here](https://cert-manager.io/docs/installation/kubernetes/).
+
+
+## Concepts
+We use [Raft Consensus Algorithm](https://raft.github.io/) to determine the leader of SQL Server Availability Group cluster. With each `mssql` container, 
+we run a sidecar container named `mssql-coordinator` which determines the leader of the cluster both on bootstrap and in fail over scenarios. 
+This works very well with the clusters having odd number of nodes. Clusters with even number of nodes still have a chance of split brain problem(Two primary node in the cluster at the same time). To avoid this split brain issue,
+we introduced an extra node named `{{db}}-arbiter`. The job of the 
+arbiter node is to participate solely in leader election.
+It doesn't store any data related to mssqlserver database. However, it needs
+a bare minimum of 1Gi~2Gi Storage for storing WAL and Snapshots that 
+are generated by RAFT. But the generation of WAL are not very frequent.
+So storage space of 2Gi is more than enough for most of the clusters.
+
+## Demo
+
+To keep things isolated, this tutorial uses a separate namespace called `demo` throughout this tutorial.
+
+```bash
+$ kubectl create ns demo
+namespace/demo created
+```
+
+Let's apply the following yaml. 
+
+```yaml
+apiVersion: kubedb.com/v1alpha2
+kind: MSSQLServer
+metadata:
+  name: ms-even-cluster
+  namespace: demo
+spec:
+  version: "2022-cu16"
+  replicas: 2
+  topology:
+    mode: AvailabilityGroup
+    availabilityGroup:
+      databases:
+        - agdb1
+        - agdb2
+  tls:
+    issuerRef:
+      name: mssqlserver-ca-issuer
+      kind: Issuer
+      apiGroup: "cert-manager.io"
+    clientTLS: false
+  podTemplate:
+    spec:
+      containers:
+        - name: mssql
+          env:
+            - name: ACCEPT_EULA
+              value: "Y"
+            - name: MSSQL_PID
+              value: Evaluation
+  storageType: Durable
+  storage:
+    accessModes:
+      - ReadWriteOnce
+    resources:
+      requests:
+        storage: 1Gi
+  deletionPolicy: WipeOut
+```
+A petset with the name `{{ dbName }}-arbiter` should be created once you apply this yaml. 
+
+```bash
+kubectl get petset -n demo
+NAME                  AGE
+ms-even-cluster          72s
+ms-even-cluster-arbiter   55s
+
+```
+
+Following a pod having name `{{ dbName }}-arbiter-0` will be created.
+
+```bash
+kubectl get pods -n demo
+NAME                    READY   STATUS    RESTARTS   AGE
+ms-even-cluster-0           2/2     Running   0          84s
+ms-even-cluster-1           2/2     Running   0          78s
+ms-even-cluster-arbiter-0   1/1     Running   0          68s
+```
+Get the pvc,
+
+```bash
+kubectl get pvc -n demo
+NAME                         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
+data-ms-even-cluster-0           Bound    pvc-8653958e-091c-4c15-8151-4d207c976ad1   1Gi        RWO            standard       2m50s
+data-ms-even-cluster-1           Bound    pvc-afd698cf-22d5-4a66-996e-a8d53198a95f   1Gi        RWO            standard       2m44s
+data-ms-even-cluster-arbiter-0   Bound    pvc-25c413c9-4cb0-4a5c-89f6-9d2208841b07   2Gi        RWO            standard       2m34s
+```
+> Note: Your pvc size for data nodes might be 1000Gi, but for most of the cases you will never need more than 2Gi storage for arbiter node.
+
+
+You can check arbiter pod has only one container by getting the pod yaml.
+```bash
+kubectl get pods -n demo ms-even-cluster-arbiter-0 -oyaml
+```
+
+## Why do we need arbiter node?
+
+Few of our users don't want to run 3 node cluster as this was quite 
+expensive for them, instead they wanted to use 2 node cluster, 
+1 primary and 1 replica. But due to raft implementation, there was chance of split brain. So we introduced this arbiter node so that they can still have 
+1 primary and 1 replica cluster and not have faced split brain problem.
+
+
+## Cleaning up
+
+```bash
+kubectl delete pg -n demo ms-even-cluster
+kubectl delete ns demo
+```
+
+## Next Steps
+- Learn more about [Raft implementation](https://github.com/etcd-io/etcd/blob/main/contrib/raftexample/README.md)
+- Learn about [backup and restore](/docs/guides/mssqlserver/backup/overview/index.md) Microsoft SQL Server database using Stash.
+- Want to set up Microsoft SQL Server cluster? Check how to [configure Highly Available Microsoft SQL Server Cluster](/docs/guides/mssqlserver/clustering/ag_cluster.md)
+- Monitor your Microsoft SQL Server database with KubeDB using [Prometheus operator](/docs/guides/mssqlserver/monitoring/using-prometheus-operator.md).
+- Detail concepts of [Postgres object](/docs/guides/mssqlserver/concepts/mssqlserver.md).
+- Want to hack on KubeDB? Check our [contribution guidelines](/docs/CONTRIBUTING.md).

docs/guides/mssqlserver/scaling/_index.md

@@ -3,7 +3,7 @@ title: Scaling Microsoft SQL Server
 menu:
   docs_{{ .version }}:
     identifier: ms-scaling
-    name: Scaling Microsoft SQL Server
+    name: Scaling SQL Server
     parent: guides-mssqlserver
     weight: 55
 menu_name: docs_{{ .version }}

docs/guides/percona-xtradb/scaling/vertical-scaling/cluster/index.md

@@ -99,7 +99,7 @@ $ kubectl get pod -n demo sample-pxc-0 -o json | jq '.spec.containers[].resource
 }
 ```
 
-You can see the Pod has the default resources which is assigned by Kubedb operator.
+You can see the Pod has the default resources which is assigned by KubeDB operator.
 
 We are now ready to apply the `PerconaXtraDBOpsRequest` CR to update the resources of this database.
 

docs/guides/postgres/arbiter/arbiter.md

@@ -12,7 +12,7 @@ section_menu_id: guides
 
 > New to KubeDB? Please start [here](/docs/README.md).
 
-# Kubedb PostgreSQL - Arbiter node for PostgreSQL cluster with even nodes
+# KubeDB PostgreSQL - Arbiter node for PostgreSQL cluster with even nodes
 
 Here we will show how to use KubeDB to provision a PostgreSQL DB with Arbiter Node.
 

docs/guides/proxysql/scaling/vertical-scaling/cluster/index.md

@@ -133,7 +133,7 @@ $ kubectl get pod -n demo proxy-server-0 -o json | jq '.spec.containers[].resour
 }
 ```
 
-You can see the Pod has the default resources which is assigned by Kubedb operator.
+You can see the Pod has the default resources which is assigned by KubeDB operator.
 
 We are now ready to apply the `ProxySQLOpsRequest` CR to update the resources of this server.
 

docs/guides/rabbitmq/scaling/vertical-scaling/vertical-scaling.md

@@ -97,7 +97,7 @@ $ kubectl get pod -n demo rm-standalone-0 -o json | jq '.spec.containers[].resou
 }
 ```
 
-You can see the Pod has default resources which is assigned by the Kubedb operator.
+You can see the Pod has default resources which is assigned by the KubeDB operator.
 
 We are now ready to apply the `RabbitMQOpsRequest` CR to update the resources of this database.
 

docs/guides/redis/backup/stash/standalone/index.md

@@ -105,7 +105,7 @@ Here, we have to use the service `sample-redis` and secret `sample-redis-auth` t
 
 ### Insert Sample Data
 
-Now, we are going to exec into the database pod and create some sample data. Kubedb has created a secret with access credentials. Let's find out the credentials from the Secret,
+Now, we are going to exec into the database pod and create some sample data. KubeDB has created a secret with access credentials. Let's find out the credentials from the Secret,
 
 ```yaml
 ❯ kubectl get secret -n demo sample-redis-auth -o yaml

docs/guides/zookeeper/scaling/vertical-scaling/vertical-scaling.md

@@ -99,7 +99,7 @@ $ kubectl get pod -n demo zk-quickstart-0 -o json | jq '.spec.containers[].resou
 }
 ```
 
-You can see the Pod has default resources which is assigned by the Kubedb operator.
+You can see the Pod has default resources which is assigned by the KubeDB operator.
 
 We are now ready to apply the `ZooKeeperOpsRequest` CR to update the resources of this database.