Communicate with Web2 app via terminal?

Targets Web
1

When I’m rolling out an update to a Web2 app, I have an administrator UI button that I can click which finds active sessions and sends them to a “Sorry, website is being rebooted” page. It works great. The only problem is I have to remember to log in and click the button.

My question is - is there a way to communicate with the WebApp via the command line? That way I could write a shell script to deploy the update, something like:

  1. tell the WebApp to notify users it’s going down
  2. kill the WebApp
  3. copy the new WebApp to the server
  4. launch the new WebApp

I’m thinking maybe I could use the kill command with a different signal?
kill -signal_name INT /path/to/my/webApp

is it possible to catch these signals in a WebApp?
(this is on macOS)

2

If you use SIGKILL the app should quit cleanly.

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3

You could catch the incoming commandline in the app.opening event, and if there’s an existing mutex, pass the command line over to the already running version of the webapp (and a 2nd instance doesn’t open). You could then take the incoming command line, use it as a trigger against user Sessions to prompt the app will be going down, and begin the back-side script to terminate, download, replace, and restart your application?

Alternatively - you could add an admin interface to the webapp or an admin-only url that causes the same events to happen? I use this method with one of our web 1.0 apps. The app knows of all remote instances and begins requesting the admin-only url to trigger each instance to begin updating at the remote-end. It then pings each application after X amount of time to ensure the app updated and restarted, otherwise, sending a notice to the instance account holder to look into the issue or manually restart their system (have only had it happen only once honestly, - due to a user caused breaking event in a linux upgrade by the user using experimental APT sources)

4

SIGKILL is too Killy. I need a few seconds to notify the sessions before the App actually quits. I might try using SIGHUP Or another signal first and then follow it later was SIGKILL

The idea of using a Mutex is interesting, but wouldn’t the second app launched be unable to bind the server port? Not sure how that would work

5

do a curl call to a special (local only) rest-call, handle it in app.handleUrl and see the host header (must be 127.0.0.1 for example)

You can do such in a script…:wink:

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6

**I would give it a test - in that case, it would cause an unhandledexception - where you could then handle the exception appropriately without a hard-crash to the mutex, do what’s needed, and end gracefully :slight_smile:

7

Alternatively - you could make the webapp port dependent on it’s opening commandline setting the port in the “restarting command line commands” that get sent - which would also prevent any port conflicts? There’s a few options available to avoid port conflicts to achieve the same.

ie)
MyApp --port=9000

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8

The app just terminates with the message it couldn’t bind to the port. I have an app that runs a cleanup cron job using the same webapp but receiving params via command line. Once Open(ing) completes it quits because of the port in use, but I personally feel safer adding a Quit to the end of the cleanup routine.

9

I think this is my favorite solution, as it would be cross-platform (assuming the ‘curl’ utility exists on your platform - does Windows have this?) I’m using macOS which definitely does.

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10

You would need to include a redistributable OpenSSL installation (contains the needed curl items for Windows machines). Current version viewable at: curl for Windows

11

I have it on windows, not sure its there by default…

12

Just confirmed with a fellow Microsoft employee that CURL as well as TAR became native to Windows 10 starting in 2018 - you should be ok! :slight_smile: Any systems/os’s prior to that, that are windows-based will require OpenSSL to be installed.

13

The curl approach is pretty easy.

In my deployment Bash script:

echo "############################################################"
echo "# Sending go_offline to WebApp"
echo "############################################################"
# note: this sends a special URL to HandleURL so we can alert all sessions that the server is going down
curl https:/example.com/go_offline?token=EAFCDEDA
sleep 1

In App.HandleURL:

select case request.Path
  case "go_offline"
    dim c as string = request.Parameter("token")
    c = c.DefineEncoding(Encodings.UTF8)

    if c = "EAFCDEDA" then
      response.MIMEType = "text/html"
      response.Write "<html><body>Going offline</body></html>"
      response.Status = 200
      call ForceUsersOffline(true)  // A method which iterates through all sessions and sends them to the "offline" webpage
      return true
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