elsa-core/src/modules/Elsa.Python/HostedServices/PythonGlobalInterpreterManager.cs

using Elsa.Python.Options;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Python.Runtime;

namespace Elsa.Python.HostedServices;

/// <summary>
/// Initializes the Python engine.
/// </summary>
public class PythonGlobalInterpreterManager : IHostedService
{
    private readonly IOptions<PythonOptions> _options;
    private readonly ILogger _logger;
    private IntPtr _mainThreadState;

    /// <summary>
    /// Initializes a new instance of the <see cref="PythonGlobalInterpreterManager"/> class.
    /// </summary>
    public PythonGlobalInterpreterManager(IOptions<PythonOptions> options, ILogger<PythonGlobalInterpreterManager> logger)
    {
        _options = options;
        _logger = logger;
    }

    /// <inheritdoc />
    public Task StartAsync(CancellationToken cancellationToken)
    {
        if (!string.IsNullOrEmpty(_options.Value.PythonDllPath)) 
            Environment.SetEnvironmentVariable("PYTHONNET_PYDLL", _options.Value.PythonDllPath);

        try
        {
            PythonEngine.Initialize();
            _mainThreadState = PythonEngine.BeginAllowThreads();
        }
        catch (Exception e)
        {
            _logger.LogWarning(e, "Failed to initialize Python engine");
        }
        
        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task StopAsync(CancellationToken cancellationToken)
    {
        if(_mainThreadState != IntPtr.Zero)
        {
            PythonEngine.EndAllowThreads(_mainThreadState);
            PythonEngine.Shutdown();
        }
        return Task.CompletedTask;
    }
}