ACTION REQUIRED: /var/log volume mounts

[Dave Protasowski]

Hey Knative Devs/Users,

Currently, we always mount an empty volume at `/var/log` which gives vendors optionality to collect logs from that location. This volume mount has a side-effect of breaking some off-the-shelf images (knative/serving#3809). 

After some discussion (knative/serving#7881) we settled on only adding the volume mount iff the operator has set logging.enable-var-log-collection to true in config-observability.

For operators:

1. If you're collecting logs make sure you have logging.enable-var-log-collection set to true

2. If you're not collecting logs make sure you have logging.enable-var-log-collection set to false.

3. Inform your app developers whether or not you are collecting these logs.

For application developers:

1. If your installation doesn't collect logs from /var/log please ensure your app/container does not stat/write anything to the old mount location. It will fail since it won't be present.

2. If your installation does collect logs from /var/log then no changes are required on your part.

Unless we hear otherwise on (knative/serving#7881) we hope to make this change in the next release (v0.20 - November 10, 2020).

thanks,

dave protasowski

[Dave Protasowski]

Just following up - I haven't heard any objection so we're continuing as planned.

thanks,

dave