Lessons learned with Add-In update execution

In our intranet we have Add-In instances installed throughout the site hierarchy. The content owners of subsites are enabled to utilize any of the provided set to their own will. In a release, IT takes care of automatic update of all the installed instances of Add-In(s) included in the release. This is done in a 2-fold approach:

• Add the updated Add-In(s) to the SharePoint Add-In catalog;
• Then first manual update ('Get It') the installed Add-In on the rootweb, for immediate result visible to end-users;
• Next, via powershell script, update all the Add-In instances in the site hierarchy: traverse through the hierarchy, and on each hostweb that has the Add-In installed, execute 'Update-SPAppInstance'. Under the SharePoint hood, this delegates the Add-In update(s) to execution via a timerjob.

We've learned 3 important lessons with this Add-In update approach:

1. The completion of the Add-In update throughout the site hierarchy is very time-consuming. In our intranet we've experienced elapse time of over 10 hours.
2. Until the full completion of the Add-In update, it is not possible to manual update the same Add-In. Situation in which you want / need to do that - and we encountered one - is when in the release it is observed that after the Add-In update, the updated Add-In has an issue. As Add-In rollback is then not longer possible (once a Add-In update is executed), the remedy is to deploy a fix (on the update/fix).
3. Most surprising: until the full completion of update of Add-In 'X', also the manual update of any other Add-In 'Y' is blocked for completion.

Lessons we took from these observations is that in intranet releases, we first complete all manual Add-In updates. This includes the potential additional installation of required 'fix' on 'updated Add-In'. And only once all manual Add-In updates are completed, and we have ascertained the effect of each is as expected; then execute the long-running Add-In update(s) via powershell maintenance script throughout the entire site hierarchy.