DOC-4753 added RDI upgrade guide

Author: andy-stark-redis

content/integrate/redis-data-integration/installation/_index.md

@@ -1,5 +1,5 @@
 ---
-Title: Installation
+Title: Install and upgrade
 aliases: /integrate/redis-data-integration/ingest/installation/
 alwaysopen: false
 categories:
@@ -10,14 +10,14 @@ categories:
 description: Learn how to install RDI
 group: di
 hideListLinks: false
-linkTitle: Installation
+linkTitle: Install/upgrade
 summary: Redis Data Integration keeps Redis in sync with the primary database in near
   real time.
 type: integration
 weight: 2
 ---
 
-The guides in this section explain the options you have for installing RDI.
+The guides in this section explain the options you have for installing and upgrading RDI.
 Before you use RDI, you must also configure your source database to use the CDC connector. See the
 [Prepare source databases]({{< relref "/integrate/redis-data-integration/data-pipelines/prepare-dbs" >}})
 section to learn how to do this.

content/integrate/redis-data-integration/installation/upgrade.md

@@ -0,0 +1,150 @@
+---
+Title: Upgrading RDI
+alwaysopen: false
+categories:
+- docs
+- integrate
+- rs
+- rdi
+description: Learn how to upgrade an existing RDI installation
+group: di
+hideListLinks: false
+linkTitle: Upgrade
+summary: Redis Data Integration keeps Redis in sync with the primary database in near
+  real time.
+type: integration
+weight: 3
+---
+
+## Upgrading a VM installation
+
+Follow the steps below to upgrade an existing
+[VM installation]({{< relref "/integrate/redis-data-integration/installation/install-vm" >}})
+of RDI:
+
+1.  Download the RDI installer from the
+    [Redis download center](https://cloud.redis.io/#/rlec-downloads)
+    (under the *Modules, Tools & Integration* dropdown) and extract it to your
+    preferred installation folder.
+
+1.  Go to the installation folder:
+
+    ```bash
+    cd rdi_install/$RDI_VERSION
+    ```
+
+1.  Run the `upgrade` script as a privileged user:
+
+    ```bash
+    sudo ./upgrade.sh
+    ```
+
+### Recovering from failure during a VM upgrade
+
+If the previous version is v1.4.4 or later, go to the `rdi_install/<NEW_VERSION>` directory
+and run `sudo redis-di upgrade`.
+
+If the version you are replacing is earlier than v1.4.4, follow these steps:
+
+1.  Run `redis-di --version` to check the current version.
+
+    If the version is the new one, copy the previous version
+    of the RDI CLI to `/usr/local/bin` with the following command:
+    
+    ```bash
+    sudo cp rdi_install/<PREVIOUS_VERSION>/deps/rdi-cli/<OS>/redis-di usr/local/bin
+    ```
+
+1.  Check that the CLI version is correct by running `redis-di --version`.
+
+    Then, go to the `rdi_install/<PREVIOUS_VERSION>` directory and run the
+    following command;
+
+    ```bash
+    sudo redis-di upgrade --rdi-host <RDI_REDIS_HOST> --rdi-port <RDI_REDIS_PORT>
+    ```
+
+{{< note >}}If the `collector-source` or the `processor` are not in the `Running` state during
+the upgrade, you must run `redis-di deploy` and check again that they are both in the
+`Running` state.
+{{< /note >}}
+
+### Upgrading a VM installation with High availability
+
+If there is an active pipeline, the upgrade process will involve upgrading RDI on the active
+VM first which will cause downtime for the collector-source (see
+[Upgrade a VM installation](#upgrade-a-vm-installation) above). Afterwards, the passive
+VM will be upgraded. Switching over won't eliminate the downtime because switching between
+VMs also requires a about a minute of downtime.
+
+## Upgrading a Kubernetes installation
+
+Follow the steps below to upgrade an existing
+[Kubernetes]({{< relref "/integrate/redis-data-integration/installation/install-k8s" >}})
+installation of RDI:
+
+1. Download the new versions of the images, if you are using a private registry:
+
+    ```bash
+    docker pull redis/rdi-processor:tagname
+    docker pull redis/rdi-operator:tagname
+    docker pull redis/rdi-api:tagname
+    docker pull redis/rdi-monitor:tagname
+    docker pull redis/rdi-collector-initializer
+    ```
+
+1.  Download the RDI helm chart tar file from the 
+    [Redis download center](https://cloud.redis.io/#/rlec-downloads).
+
+1.  Run the `helm upgrade` command:
+    
+    ```bash
+    helm upgrade [RELEASE_NAME] [CHART]
+    ```
+
+    Note that you don't need to
+    [deploy]({{< relref "/integrate/redis-data-integration/data-pipelines/deploy" >}})
+    again after this step.
+
+1.  Download the latest `redis-di`.
+
+### Verifying the upgrade
+
+Check the upgrade with the following command:
+
+```bash
+ sudo k3s kubectl get all -n <namespace>
+```
+
+You should find that all the pods are running (they will have `1/1` in the `READY` column of the
+command's output).
+
+You can also check that the latest version is running using the following command on one of
+the pods:
+
+```bash
+sudo k3s kubectl describe <pod_name> -n <namespace>
+```
+
+Search for the image tag `Image: docker.io/redis/<pod_name>:<version/image_tag>`
+in the command's output to verify the version
+
+### Recovering from failure during a Kubernetes upgrade
+
+If you get an error during the upgrade or some deployments are not OK, then
+run the `helm upgrade` command again, but with the previous version you were upgrading
+from.
+
+## What happens during the upgrade?
+
+The upgrade process replaces the current RDI components with the new versions:
+
+-   Firstly, the control plane components are replaced. At this point, the pipeline
+    is still active but monitoring will be disconnected.
+
+-   Secondly, the pipeline data path components are replaced with the new versions.
+    If a pipeline is active while upgrading, the `collector-source` will be restarted
+    as a result of restarting the `collector-initializer`. The pipeline will pause for
+    about two minutes but it will catch up very quickly after restarting. 
+    The pipeline data and state are both stored in Redis, so data will never normally
+    be lost during the downtime while upgrading.