Deploying extractor as windows servie

The installer template has built in support for creating a windows service using the same executable as the standalone version. This requires some setup, as the extractor must report its status to windows.

This setup requires the following packages:

• Microsoft.Extensions.Hosting
• Microsoft.Extensions.Hosting.WindowsServices
• Microsoft.Extensions.Logging.EventLog

It might also be useful to use System.CommandLine for parsing command line arguments, though that will not be covered here.

The idea is to launch the extractor as a service if passed a specific command line argument, like --service, and launch it as standalone otherwise. The code could be as follows:

public class Worker : BackgroundService
{
    private readonly ILogger<Worker> _eventLog;
    
    public Worker(ILogger<Worker> eventLog)
    {
        _eventLog = eventLog;
    }
    
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await ExtractorRunner.Run(
            "config.yml",
            null,
            "myExtractor",
            "myExtractor/1.0.0",
            false,
            true,
            true,
            true, // We don't really want the service to die too quickly
            stoppingToken,
            null,
            null,
            null,
            _eventLog // Pass the eventlog as startup logger
        );
    }
}

public static class Program
{
    static void Main(string[] args)
    {
        if (args[0] == '--service')
        {
            RunService();
        }
        else
        {
            RunStandalone();
        }
    }
    
    private static void RunService()
    {
        var builder = Host.CreateDefaultBuilder()
            .ConfigureServices((hostContext, services) =>
            {
                services.AddHostedService<Worker>();
            });
        if (OperatingSystem.IsWindows())
        {
            builder = builder
                .ConfigureLogging(loggerFactory => loggerFactory.AddEventLog())
                // It is very important that this is equal to "product_short_name" in the installer template
                .UseWindowsService(options => options.ServiceName == "MyExtractor");
        }
        builder.Build().Run();
    }
    
    private static void RunStandalone()
    {
        // Run extractor as usual.
    }
}

In the installer template config file, set

• product_short_name equal to "MyExtractor" (the same as you used for the service name)
• service to true
• service_args to --service (the argument to run as service)

Running multiple service instances

The easiest way to run multiple service instances is to add an argument --working-dir which indicates where the extractor should look for the config file, then pass that to Run.

Services can then be created using something like

sc create myextractor1 binPath="path/to/exe --service --working-dir path/to/config" DisplayName="My Extractor 1"

Running services on Linux.

Technically any application can run as a service with no extra setup, but it is good practice to run the extractor as a daemon. Fortunately this is simple using Microsoft.Extensions.Hosting.Systemd. Just add

else if (OperatingSystem.IsLinux())
{
    builder = builder.UseSystemd();
}

to RunService().

Next, add a file my-extractor.service to /etc/systemd/system/ which should look something like this:

[Unit]
Description=MyExtractor Service
After=network.target # Network is a fine dependency for most extractors
StartLimitIntervalSec=0

[Service]
Type=simple
Restart=always
RestartSec=1
ExecStart=/path/to/extractor --service --working-dir path/to/config

[Install]
WantedBy=multi-user.target

To start you should now be able to do sudo systemctl start my-extractor.

Running multiple services on linux

On linux running multiple extractors can be done trivially using service templates.

Add another file to /etc/systemd/system/ named my-extractor@.service.

[Unit]
Description=MyExtractor Service (%I)
After=network.target # Network is a fine dependency for most extractors
StartLimitIntervalSec=0

[Service]
Type=simple
Restart=always
RestartSec=1
ExecStartPre= mkdir -p /path/to/config/%i/
ExecStart=/path/to/extractor --service --working-dir path/to/config/%i/

[Install]
WantedBy=multi-user.target

Very similar to the normal version, except now we take an extra argument as a parameter and create a named folder for each instance of the extractor containing the working directory.

Installing on linux

It is worth mentioning the proper way to install system applications on linux. Unlike windows having a single "working directory" is not considered normal or good practice. Instead, you should use the following directories:

• /etc/company/myextractor for configuration files.
• /var/log/company/myextractor for logs.
• /var/lib/company/myextractor for the working directory, if you need one. This can contain temporary files and symlinks to logs and config files.
• /usr/bin for the executable.

Setup of the extractor might be the following:

mkdir -p /var/lib/company/myextractor/
mkdir -p /var/log/company/myextractor/
mkdir -p /etc/company/myextractor/
ln -sfn /etc/company/myextractor/ /var/lib/company/myextractor/config
ln -sfn /var/log/company/myextractor/ /var/lib/company/myextractor/logs
/usr/bin/my-extractor --service --working-dir /var/lib/company/myextractor/

To actually create installers, you will typically create both RPM and DEB installers, which are the two most common types.