Fixing the FTL information on settings page after a FTL restart

[rdwebdesign]

What does this PR aim to accomplish?

This PR tries to fix a behavior affecting some installations (docker and bare metal) where the web interface button "Restart DNS resolver" causes an apparent error, while restarting FTL.

This topic from Discourse shows the problem on a bare metal install:
https://discourse.pi-hole.net/t/restart-dns-resolver-is-killing-new-ftl/60693

The real issue:
FTL is restarted, but in some cases the PHP page is reloaded before FTL is completely restarted.
The page uses the function pidofFTL() to read the PID, but the value is not found and "FTL is offline" message is shown.

A few milliseconds after that, FTL finishes the restart process, but in some cases the restart could take seconds to finish.

Screen capture showing the behavior:

How does this PR accomplish the above?

Adding a new message and a countdown to wait for FTL to restart.

Link documentation PRs if any are needed to support this PR

none

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[DL6ER]

FTL is restarted, but in some cases the PHP page is reloaded before FTL is completely restarted.

To me this sounds like the real fix would rather be delaying the reload. This is what others do, too, for instance my router: when I click on the restart button, it shows some 10 seconds countdown before it allows any further actions on the page. The countdown is ticking down so users don't get impatient thinking that maybe nothing is happening and something has frozen.

Mind that FTL may need longer than one second to restart on low end services with very many queries within 24 hours a it has to reload then after a restart.

[rdwebdesign]

Well, this is actually delaying the reload, but only for a few milliseconds.

Reading your comment, I think we could simply add a third state.

The current PHP page shows 2 states:

• FTL service is offline (in case no PID is found) or
• the normal page with all values.

We could introduce a new state using a message "FTL is restarting...".

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/restart-dns-resolver-is-killing-new-ftl/60693/32

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/the-ftl-service-is-offline-on-two-separate-raspi-using-docker-and-unbound/62095/6

[rdwebdesign]

Branch was updated.