<!-- don't edit here, it's from https://@github.com/arangodb/kube-arangodb.git / docs/Manual/ -->
# Start ArangoDB Cluster to Cluster Synchronization on Kubernetes

This tutorial guides you through the steps needed to configure
an ArangoDB datacenter to datacenter replication between two ArangoDB
clusters running in Kubernetes.

{% hint 'info' %}
This feature is only available in the
[**Enterprise Edition**](https://www.arangodb.com/why-arangodb/arangodb-enterprise/)
{% endhint %}

## Requirements

1. This tutorial assumes that you have 2 ArangoDB clusters running in 2 different Kubernetes clusters.
1. Both Kubernetes clusters are equipped with support for `Services` of type `LoadBalancer`.
1. You can create (global) DNS names for configured `Services` with low propagation times. E.g. use Cloudflare.
1. You have 4 DNS names available:
   - One for the database in the source ArangoDB cluster. E.g. `src-db.mycompany.com`
   - One for the ArangoDB syncmasters in the source ArangoDB cluster. E.g. `src-sync.mycompany.com`
   - One for the database in the destination ArangoDB cluster. E.g. `dst-db.mycompany.com`
   - One for the ArangoDB syncmasters in the destination ArangoDB cluster. E.g. `dst-sync.mycompany.com`

## Step 1: Enable Datacenter Replication Support on source ArangoDB cluster

Set your current Kubernetes context to the Kubernetes source cluster.

Edit the `ArangoDeployment` of the source ArangoDB clusters.

Set:

- `spec.tls.altNames` to `["src-db.mycompany.com"]` (can include more names / IP addresses)
- `spec.sync.enabled` to `true`
- `spec.sync.externalAccess.masterEndpoint` to `["https://src-sync.mycompany.com:8629"]`
- `spec.sync.externalAccess.accessPackageSecretNames` to `["src-accesspackage"]`

## Step 2: Extract access-package from source ArangoDB cluster

Run:

```bash
kubectl get secret src-accesspackage --template='{{index .data "accessPackage.yaml"}}' | \
  base64 -D > accessPackage.yaml
```

## Step 3: Configure source DNS names

Run:

```bash
kubectl get service
```

Find the IP address contained in the `LoadBalancer` column for the following `Services`:

- `<deployment-name>-ea` Use this IP address for the `src-db.mycompany.com` DNS name.
- `<deployment-name>-sync` Use this IP address for the `src-sync.mycompany.com` DNS name.

The process for configuring DNS names is specific to each DNS provider.

## Step 4: Enable Datacenter Replication Support on destination ArangoDB cluster

Set your current Kubernetes context to the Kubernetes destination cluster.

Edit the `ArangoDeployment` of the source ArangoDB clusters.

Set:

- `spec.tls.altNames` to `["dst-db.mycompany.com"]` (can include more names / IP addresses)
- `spec.sync.enabled` to `true`
- `spec.sync.externalAccess.masterEndpoint` to `["https://dst-sync.mycompany.com:8629"]`

## Step 5: Import access package in destination cluster

Run:

```bash
kubectl apply -f accessPackage.yaml
```

Note: This imports two `Secrets`, containing TLS information about the source cluster,
into the destination cluster

## Step 6: Configure destination DNS names

Run:

```bash
kubectl get service
```

Find the IP address contained in the `LoadBalancer` column for the following `Services`:

- `<deployment-name>-ea` Use this IP address for the `dst-db.mycompany.com` DNS name.
- `<deployment-name>-sync` Use this IP address for the `dst-sync.mycompany.com` DNS name.

The process for configuring DNS names is specific to each DNS provider.

## Step 7: Create an `ArangoDeploymentReplication` resource

Create a yaml file (e.g. called `src-to-dst-repl.yaml`) with the following content:

```yaml
apiVersion: "replication.database.arangodb.com/v1alpha"
kind: "ArangoDeploymentReplication"
metadata:
  name: "replication-src-to-dst"
spec:
  source:
    masterEndpoint: ["https://src-sync.mycompany.com:8629"]
    auth:
      keyfileSecretName: src-accesspackage-auth
    tls:
      caSecretName: src-accesspackage-ca
  destination:
    deploymentName: <dst-deployment-name>
```

## Step 8: Wait for DNS names to propagate

Wait until the DNS names configured in step 3 and 6 resolve to their configured
IP addresses.

Depending on your DNS provides this can take a few minutes up to 24 hours.

## Step 9: Activate replication

Run:

```bash
kubectl apply -f src-to-dst-repl.yaml
```

Replication from the source cluster to the destination cluster will now be configured.

Check the status of the replication by inspecting the status of the `ArangoDeploymentReplication` resource using:

```bash
kubectl describe ArangoDeploymentReplication replication-src-to-dst
```

As soon as the replication is configured, the `Add collection` button in the `Collections`
page of the web UI (of the destination cluster) will be grayed out.