[t] Indicate Tailscale install requirement #2845

[phillxnet]

Introduces tailscale binary os.path.isfile sensitivity to inform the associated Web-UI errors: enabling more context regarding our NOT pre-installing tailscale.

Fixes #2845

[phillxnet]

Testing

Behaviour appear as-was with a "Tailscale install" as per our recent how-to: https://rockstor.com/docs/howtos/tailscale_install.html

Without Tailscale installed

1. Fresh-install (rpm origin)
2. Enable Tailscale

Result is display of Tailscale config dialog

3 Submit defaults:

Houston, we've had a problem.
Tailscale is NOT installed by default. See docs How-tos & guides: `Tailscale install` https://rockstor.com/docs/howtos/tailscale_install.html

            Traceback (most recent call last):
  File "/opt/rockstor/src/rockstor/smart_manager/views/tailscaled_service.py", line 101, in post
    systemctl(self.name, "stop")
  File "/opt/rockstor/src/rockstor/system/services.py", line 107, in systemctl
    return run_command(arg_list, log=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/rockstor/src/rockstor/system/osi.py", line 290, in run_command
    raise CommandException(cmd, out, err, rc)
system.exceptions.CommandException: Error running a command. cmd = /usr/bin/systemctl stop tailscaled. rc = 5. stdout = ['']. stderr = ['Failed to stop tailscaled.service: Unit tailscaled.service not loaded.', '']

Close all dialogs

1. Tailscale configure (spanner)
2. Submit defaults

Result is as above.

N.B. I was expecting a FileNotFound in one of the above. Looking into this now.

However: Ready for review as does catch and inform folks:

Tailscale is NOT installed by default. etc

and given, info on how to install. A link would be better: but we do have a doc link via the I icon in the config dialog: which in turn links to the same how-to.

[phillxnet]

N.B. I was expecting a FileNotFound in one of the above. Looking into this now.

In order to trigger this we look to the code comment:

       # Account for install with restored Tailscale config, but no Tailscale installed.

With a fresh install there is no config: and we error out with the prior exception when initially trying to adding one (with no Tailscale install) as per the last comments details.

1. Install Tailscale as per How-to in error message: https://rockstor.com/docs/howtos/tailscale_install.html
2. Tailscale spanner - submit config defaults: On/Off replaced by Login button.
3. zypper --non-interactive remove tailscale
4. Tailscale "Login" button is replaced by On/OFF (auto-refresh active on services page).
5. Switch service On (not blocked by config due to above arrangements) - but we trigger the missing tailscale binary fence: FileNotFoundError.

Houston, we've had a problem.
Tailscale is NOT installed by default. See docs How-tos & guides: `Tailscale install` https://rockstor.com/docs/howtos/tailscale_install.html

            Traceback (most recent call last):
  File "/opt/rockstor/src/rockstor/smart_manager/views/tailscaled_service.py", line 130, in post
    tailscale_up(config=config)
  File "/opt/rockstor/src/rockstor/system/tailscale.py", line 69, in tailscale_up
    tailscale_not_found()
  File "/opt/rockstor/src/rockstor/system/tailscale.py", line 58, in tailscale_not_found
    raise FileNotFoundError
FileNotFoundError

[phillxnet]

An rpm originating install was setup on both a 15.5 and 15.6 (both X86_64) install and both were Web-UI configured & enabled to participate in a Tailscale network. They were then able to ping one-another using the Tailscale assigned IPs. Serving as a test to ensure we still have successful Tailscale default config / enable / Login capability via the Web-UI only.

Thanks again to @FroggyFlox for this Tailscale UI implementation/addition. I'm not entirely happy with my modifications here: but they serve an informational purpose which was the aim of the linked issue. We can re-address the in-elegance of only catching exceptions here once we have begun our HTMX 2.0 introduction and enabled SSEs to more interactively/proactively indicate a service's installed state. Enabling far smaller install options in the future. But for now we needed to inform folks of this services non-default install status: our first service of this kind.

[FroggyFlox]

@phillxnet,
I won't have time to test it myself but your extensive testing and report make me confident it's all good!
I do agreed it's still not the best user experience but it is definitely a big improvement over the current situation and it lays the foundation for a much better and dynamic user experience down the road once we have a proper messaging/notification system in place.

Thanks for taking care of this one too!