I received notification this morning at 08:02 that there was an availability error in my application. The App Service could not reach the container via the ip address I had configured, 10.24.2.5. I login to the portal to check and it seems the ip address of my container instances has changed to 10.24.2.4. According to the documentation
If the container group is stopped, started, or restarted, the container group's private IP is subject to change. If this happens, you will need to update the application gateway configuration.
I do not know why my container group was stopped, started or restarted, however I noticed a couple of events in the log which coincide with the time the incident occurred.
This is strange to me, as there was nothing I did overnight to prompt azure container instances to try and fetch a new image. The image it's pulling is hosted in an Azure Container Registry, and from the portal we can see that this image has not changed since June 2020 and so pulling should not cause any stop/start/restart to occur.
Can someone please explain why in the middle of the night, azure container instances takes it upon itself to try and pull a new version of my image, restarts itself and then gets a new ip address?