If we get an error we'll only hold the deploy lock if it occurs while
trying to switch the running containers.
We'll also move tagging the latest image from when the image is pulled
to just before the container switch. This ensures that earlier errors
don't leave the hosts with an updated latest tag while still running the
older version.
Add a deploy lock for commands that are unsafe to run concurrently.
The lock is taken by creating a `mrsk_lock` directory on the primary
host. Details of who took the lock are added to a details file in that
directory.
Additional CLI commands have been added to manual release and acquire
the lock and to check its status.
```
Commands:
mrsk lock acquire -m, --message=MESSAGE # Acquire the deploy lock
mrsk lock help [COMMAND] # Describe subcommands or one specific subcommand
mrsk lock release # Release the deploy lock
mrsk lock status # Report lock status
Options:
-v, [--verbose], [--no-verbose] # Detailed logging
-q, [--quiet], [--no-quiet] # Minimal logging
[--version=VERSION] # Run commands against a specific app version
-p, [--primary], [--no-primary] # Run commands only on primary host instead of all
-h, [--hosts=HOSTS] # Run commands on these hosts instead of all (separate by comma)
-r, [--roles=ROLES] # Run commands on these roles instead of all (separate by comma)
-c, [--config-file=CONFIG_FILE] # Path to config file
# Default: config/deploy.yml
-d, [--destination=DESTINATION] # Specify destination to be used for config file (staging -> deploy.staging.yml)
-B, [--skip-broadcast], [--no-skip-broadcast] # Skip audit broadcasts
```
If we add support for running multiple deployments on a single server
we'll need to extend the locking to lock per deployment.
`docker image ls` doesn't tell us what the latest deployed image is (e.g
if we've rolled back). Pull the latest image tag through to the server
so we can use it instead.
