cloudmelon / functions-dotnet-migrating-console-apps

A generic azure function that can be used to convert any console application to an HTTP webservice

services	platforms	author
functions	dotnet	muralivp

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Run Console Apps on Azure Functions

tldr: Here is an easy way of getting any .exe running as a web service. You just specify the input parameters to your exe in a configuration file. You can use binary files as inputs to the exe by specifying a URL to download it from.

More details: This sample is a generic function (.csx file) that can be used to convert any console application to an HTTP webservice in Azure Functions. All you have to do is edit a configuration file and specify what input parameters will be passed as arguments to the .exe.

Azure functions is an offering from Microsoft that allows you to create serverless "compute on demand" applications.

Features

• You can use binary files as input (specify the URL and the binary file will be downloaded to a temporary location on the virtual environment hosting your Azure Function)
• You choose which file is sent back to the user as output
• Here's what the configuration file looks like (more details later)

{
    "name": "consoleAppToFunctions",
    "input": {
        "command": "ffmpeg.exe -i {inputFile} {output1}",
        "arguments": {
            "inputFile": {
                "url": "https://1drv.ms/v/<link-to-file>"
                //binary file input
            },
            "output1": {
                "localfile": "out.mp3"
                //stored in a temp folder
            }
        }
    },
    "output": {
        "folder": "outputFolder",
        "binaryFile": {
            "returnFile": "*.mp3",
            "returnFileName": "yourFile.mp3"
        }
    }
}

Getting Started - Creating a new Function App

1. Login to - Azure Portal
2. Create a function app by specifying an App Name and storage account

3. Go to the function code editor and Create a New Function

4. Select HTTPTrigger - C# and name your function ConsoleAppToFunction with the right Authorization Level

Adding Code

TL;DR
If you don't care about the details, just go to your function's "Your Files > Upload Files" (top right) and upload the 3 files in the code sample along with the .exe (and .dll's it requires)

The following are steps that you should follow if you want to fimiliarinze yourself with the using Azure functions interface.

1. Select the run.csx file under View files

2. Replace the code in Run.csx with ConsoleApp Function Code

3. Since the code uses Json.Net, create a Project.Json file.

Configuring the Sample

We have now created a generic function that can run any console application. You can specify which console app to run in a file called FunctionConfig.json in the following example config we specify the function to run FFMpeg.exe

{
    "name": "consoleAppToFunctions",
    "input": {
        "command": "ffmpeg.exe -i {inputFile} {output1}",
        "arguments": {
            "inputFile": {
                "url": "https://1drv.ms/v/<link-to-file>"
            },
            "output1": {
                "localfile": "out.mp3"
            }
        }
    },
    "output": {
        "folder": "outputFolder",
        "binaryFile": {
            "returnFile": "*.mp3",
            "returnFileName": "yourFile.mp3"
        }
    }
}

We needed a way to pass binary input files to our function. For this we define an argument of type url, where we expect the user to upload a file to Onedrive (or whatever service that hosts a binary file) and provide the link in the query string.

Once these changes are done, the function should have the following files as shown below:

Interacting with the function

1. Upload your test input file(s) to OneDrive
2. Get a link to the file using the OneDrive Share menu - something like https://1drv.ms/v/
3. Interact with the function providing the inputs as querystring. Note that inputFile here is defined in the FunctionConfig.json file above

Example URL:

https://[the URL when you click 'Get Function URL']&inputFile=<link-to-onedrive-file>

The function will process this request by invoking the specified console app and provide the output as a file download.