Decrease watchtower Polling Interval and Add Orphaned Image Cleanup

[ThorntonMatthewD]

Summary

Adds the following environmental variables to the watchtower service:

Env Var	Description	Value
WATCHTOWER_POLL_INTERVAL	The number of seconds between when watchtower will look for new images.	900 (15 minutes)
WATCHTOWER_CLEANUP	Determines whether or not old images should be removed after they have been updated.	true

[oliviasculley]

Looks good! Docker's free/anonymous pull limit is 100 pulls / 6 hours, but this is well under that, and you can log in with a docker account for 200 pulls / 6 hours as well.

[ThorntonMatthewD]

@oliviasculley I did not know that! I think we'll be running at ~72 pulls/6 hours currently for just the Slack bot setup. I wonder if we should exclude autoheal and watchtower from being polled.

I didn't see any other containers running in the screenshot that Jim posted earlier in the channel, but do you know if there are others? I think watchtower will look for updates for anything running on the same daemon.

[allella]

@ThorntonMatthewD @oliviasculley

With this docker-compose.yml being an example of what the file should look like, are we missing some values in this example that exist in production environment.

For example, the production slack-events bot looks like this, with more than two environment values set in that section.

      - BOT_TOKEN=value
      - SIGNING_SECRET=value
      - PORT=7331
      - TZ=US/Eastern
      # Poll for image updates every 15 minutes
      - WATCHTOWER_POLL_INTERVAL=900
      # Cleans up orphaned images upon pulling new ones
      - WATCHTOWER_CLEANUP=true

[allella]

Nevermind, the GitHub collapsing of the file was confusing me and thinking the "environment" change was part of the environment in the slack-events-bot section.