When an automatic upgrade completes, or when the user clicks on the upgrade
button in one webapp, but also has it open in another browser window/tab,
we have a problem: The current web server is going to stop running in
minutes, but there is no way to send a redirect to the web browser to the
new url.
To solve this, used long polling, so the webapp is always listening for
urls it should redirect to. This allows globally redirecting every open
webapp. Works great! Tested with 2 web browsers with 2 tabs each.
May be useful for other purposes later too, dunno.
The overhead is 2 http requests per page load in the webapp. Due to yesod's
speed, this does not seem to noticibly delay it. Only 1 of the requests
could possibly block the page load, the other is async.
Made alerts be able to have multiple buttons, so the alerts about upgrading
can have a button that enables automatic upgrades.
Implemented automatic upgrading when the program file has changed.
Note that when an automatic upgrade happens, the webapp displays an alert
about it for a few minutes, and then closes. This still needs work.
Not yet wired up to restart the assistant on upgrade; that needs careful
sanity checking to wait until the upgrade is done before restarting.
Used the DirWatcher here, so it gets events for any changes to the
directory containing the program file. (But not subdirs.) This is necessary
in order to detect when the file is renamed as part of the upgrade, which
an inotify on a single file would not detect. (Also, I have DirWatcher code,
but not FileWatcher code.)
Note that upgrades that remove or rename a whole directory tree containing
the executable will *not* trigger this code. So eg, deleting and replacing
the whole standalone tarball dir tree won't work -- but untarring it
over top will. So should dpkg package upgrades.
Added programPath, using a new GHC feature to find the full path to the
executable. The fallback code for old GHC or unsupported OS is less good;
its worst failure mode would be either failing to find the program, and so
not checking for upgrades, or finding a git-annex that's in PATH, but is
not the one running.
This commit was sponsored by John Roepke.
In 0.9, -v shows version, rather than controlling verbosity.
Still need to port to 0.9, this just avoids massively confusing addurl when
quvi prints its version and exits successfully, on urls that it cannot be
used with.
