UPS Power Failure Alert

For my server I am using an APC uninterruptible power supply for protection against blackouts and other power related issues. I built on my previous projects with Microsoft Flow to get a notification on my phone when my server loses mains power and when it regains it.

The UPS

The software provided by APC with the UPS allows for basic functionality when power was lost, such as shutting down the computer before all battery power was exhausted. However, it did not provide any more advanced features, such as being able to run a script when mains power was lost or restored.

Fortunately, the software was creating application event logs when these conditions occurred. After some research and trial and error, I was able to deduce an application event with an event ID of 174 was produced when the mains power failed and an application event with an event ID of 61455 was produced when the mains became available again. (Both of these event logs came from the source of “APC UPS Service”)

Scheduling the Alert

To generate a notification in response to one of these events, I created a simple task in Windows inbuilt task scheduler. This task looked for the specified event ID and as an action run my notification PowerShell script that I created previously (see the previous blog post for details about the script).

The procedure goes as follows:

  • Open task scheduler in Windows and click the link to create a basic task
  • Give the new task a name and description and click the next button
  • For the trigger, select the option “When a specific event is logged”
  • Configure the event log for task manager to look for
    • Select “Application” as the log type from the drop down menu
    • In the source box enter “APC UPS Service”
    • In the event ID enter either “174” for a notification on mains power failure or “61455” for a notification on mains power restoration
  • Configure the action to be performed when this task runs
    • Select the radio button for “Start a program”
    • In the “Program/script” section, enter “powershell.exe”
    • In the “Add arguments” enter the full path to the PowerShell notification script created earlier.
    • Note: It is very important that you provide “powershell.exe” as the program to start. If you simply put the path to your script in this box, your PowerShell script will be opened in notepad when your task runs and not actually executed. This is just a feature of Windows and you will notice the same action if you double click on your PowerShell script.
  • Optionally repeat the process for the other event ID so notification will be generated for both power failure and power restoration.

JSON Web POST with PowerShell

An alternative to my previous method of using Python to make web requests for the notifications is to use PowerShell. The main advantage of using PowerShell is that it is included with Windows systems and therefore does not require the installation of any other packages. Additionally, it is far easier to trigger the script to run using the likes of Window’s task scheduler, allowing notifications to be triggered in response to events on the Windows system.

My Script

  • The first task is to once again define the URL from which the requests will be made
    • This can be found in the Flow interface under the “When HTTP request is received section” and will be unique for each flow
    • In PowerShell, variables are assigned and referenced with the “$” sign in front of them
    • $URL = "https://prod-02.australiasoutheast.logic.azure.com:443/workflows/a7.....
  • Next I define a “Parameters” object to contain the parameters I want to include in the notification
    • Note: The syntax used here is to create a PowerShell object, and not JSON. It will need to be converted to JSON in the next step
    • $Parameters = @{
       "Source"= "Computer"; 
       "Message"= "42";
      }
    • Again I am using “Computer” as the source and “42” as the message, however this will be where you can add your own custom information.
  • Next we get PowerShell to take the parameters object we just created and turn it into a JSON object
    • $JSON = $Parameters | ConvertTo-Json
    • The result is stored in the “JSON” variable
  • Finally, we perform the actual web request
    • Invoke-WebRequest -Uri $URL -Method POST -Body $JSON -ContentType 'application/json'

Device Notification with Microsoft Flow

For a couple of IoT projects I’ve been working on, I wanted to allow scripts to trigger a notification on my phone. I evaluated a number of solutions, but many of them were paid services that only served that particular purpose. Additionally, many of them did not include the ability to customise the notifications.

A solution presented itself when I began to look at creating workflows with Microsoft Flow, which is included in an Office 365 for business subscription. Microsoft Flow basically allows for a trigger event to cause a number of actions. In this case there was a trigger that could be activated when a web request was made to a specific URL and one of the actions was to trigger a notification on a phone. Additionally, by including a JSON POST in the request, it was possible to modify the content of the notification. As a point of interest you could also send an email with almost the same setup if it would better suit the application.

Procedure

  1. Login to your Office 365 portal (portal.office.com)
  2. Click on the Flow link
  3. Click the button for “Create from blank”
  4. Search for the “When a HTTP request is received” trigger and add it to the flow
  5. Create the JSON Schema
    1. This is probably the most complicated part of the whole procedure as you need to define the JSON structure that will be used to provide parameters for your notification
    2. For my notification system, I only wanted to provide two parameters:
      1. A source field for the device or application sending me a message
      2. A message field for the contents of the actual message
    3. The JSON structure for these two fields looked likes the following:
      {
      
      "type": "object",
      
      "properties": {
      
      "Source": {
      
      "type": "string"
      
      },
      
      "Message": {
      
      "type": "string"
      
      }
      
      }
      
      }
    4. Note: You could create a far more advanced structure if you wanted more information in your notifications
  6. Now the trigger is fully configured you will need to add an action
    1. In this case, we will add the “send me a mobile notification” action
    2. It’s important to note that this requires you have the Microsoft Flow app installed on your mobile phone.
  7. Next we need to configure the notification action
    1. The only field we need to populate is the Text field which will be displayed as the body of the notification
    2. We could add an arbitrary text string into the field if we only ever want one message to be displayed, however we can reference the variables we created earlier in the JSON Schema to make the message more meaningful.
    3. For example with regard to my JSON schema, I created the message “Source has said Message”
      1. You will notice that the variables outlined in the JSON schema will appear as different symbols in the text, confirming that flow has recognised them as the variables above.
      2. It should look something like the following:Capture
      3. When the notification is generated the source and message placeholders will be replaced by the information you provide in the web request.
  8. Finally save the workflow
    1. This will generate a unique URL that you will make a web request to and will then trigger the notification.
    2. The whole flow should look something like this one:Capture

You will now have a working notification system. Simply install the flow app on your phone, sign into it using the same Microsoft account and make a request to the specified URL. A future blog post will go into detail about how to make a web request and provide the necessary JSON parameters using a number of scripting languages.