Continuously run powershell to get disk free space

[lukebakken]

Much faster than starting it every time.

Fixes #4140.

Update: this has been superseded by #5241.

[michaelklishin]

Free disk space monitoring on Windows, again 😢

[lukebakken]

Marking as a draft again, I just thought of something.

[lukebakken]

Here's how I built the windows packages from Linux:

make FULL=1 RABBITMQ_PACKAGING_REPO="$HOME/development/rabbitmq/rabbitmq-packaging" UNIX_TO_DOS=unix2dos package-windows

I had to use UNIX_TO_DOS since I don't have the usual todos package.

Then, extract the zip file and start up RabbitMQ. In powershell, I did this:

Config file:

log.console = true
log.console.level = debug
log.file.level = debug

Commands:

$env:RABBITMQ_ALLOW_INPUT='true'
$env:RABBITMQ_CONFIG_FILE='C:\Users\bakkenl\conf\rabbitmq.conf'
.\sbin\rabbitmq-server.bat

In the interactive Erlang terminal, you can run the following to see that the free disk space has been retrieved:

rabbit_disk_monitor:get_disk_free().

You can bring up a program like Task Manager or Process Explorer to see the running powershell instance:

Go ahead and kill it and you will see it be restarted.

[dumbbell]

I tested this branch on a Windows 10 and it worked as advertised. Killing the PowerShell process also worked and rabbit_disk_monitor:get_disk_free() continued to report the correct value.

[dumbbell]

Well done! This is really cool

[lukebakken]

Thanks @dumbbell for the review!

[lukebakken]

@dumbbell @michaelklishin my next step was to look into disksup in Erlang/OTP itself. Currently, you can only enable disk monitoring down to the minute, BUT, if you start os_mon, look at what you can get:

Eshell V13.0.2  (abort with ^G)
1> os_mon_sysinfo:get_disk_info().
** exception exit: {noproc,{gen_server,call,[os_mon_sysinfo,get_disk_info]}}
     in function  gen_server:call/2 (gen_server.erl, line 367)
2> application:ensure_all_started(os_mon).
{ok,[sasl,os_mon]}
3> os_mon_sysinfo:get_disk_info().        
["C:\\ DRIVE_FIXED 720577376256 1013310287872 720577376256\n"

AHA! Much better than Powershell. It uses a port program called win32sysinfo.exe:

https://github.com/erlang/otp/blob/master/lib/os_mon/c_src/win32sysinfo.c

Expect an updated set of changes for free disk on Win32.

[inikulshin]

@lukebakken @michaelklishin is this PR (and #5241) planned to be merged into 3.9?