Rolling upgrade

  Written by The Jahia Team
 
Sysadmins
   Estimated reading time:

1. Introduction

Platform upgrade is a key aspect of a platform high availability. While it is essential to ensure that a platform stays up-to-date at all time (for a number of reasons ranging from security, to performance improvements and getting the latest fancy features released in each version), platform upgrade can also mean service downtime. 
The rolling upgrade presented here allows to use the existing servers and update them on a one-by-one basis while serving HTTP traffic with the remaining computation power.

rolling.gif

(click on the image to watch the animation)

2. Prerequisites

The procedure works with the following DX target versions:

  • 7.3.0.0 and later
  • 7.2.3.2 and later

3. Detailed procedure

Let’s consider the following environment: a cluster of 3 nodes in the version X behind a load balancer (represented by the 

nginx.PNG
 logo). The procedure will explain step by step how to migrate it to the version X+1 without service disruption.

It is advised to perform this procedure during a period of low activity and traffic, as it requires to use the full read-only mode and to remove a node from the load balancer at any time during the upgrade procedure.

  1. The environment is in its initial state:
    upgrade-1.png

     
  2. Turn all nodes of the cluster in full read-only mode. The procedure is described here.
     
  3. Create a backup of your environment.
     
  4. Create a copy of the database, in what we’ll call “DB Schema B”
    Your environment is now in the following state:
    upgrade-4.png

     
  5. Remove the processing node from the load balancer, so it does not serve any request:
    upgrade-5.png

     
  6. Stop the processing node.
     
  7. Point the processing node to the copied database “DB Schema B”:
    upgrade-7.png

     
  8. Migrate the processing node.
     
  9. Before restarting the node, create a marker file (empty file) named "rolling-upgrade" in the <digital-factory-data> folder. This will prevent any conflict with the other nodes. The description of this marker is available here.
  10. Restart the node. Note that the node will not be in full read-only mode anymore.
    upgrade-10.png

     
  11. Traffic can be redirected to this node:
    upgrade-11.png

     
  12. Repeat the steps 5 to 12 for the other, non processing, nodes (remove from load balancer, stop, point to migrated database, migrate the node, create backup-restore file and restart):
    upgrade-final.png

     
  13. Your environment is now migrated to the newer version!