Simple Heartbeat

appsettings.json

{
  "Heartbeat": {
    "Enabled": true,
    "IntervalSeconds": 60,
    "LogFile": "C:\\logs\\heartbeat.log",
    "HealthUrl": "https://localhost/health",
    "ConnectionString": "Server=localhost;Database=AppDb;Trusted_Connection=True;"
  }
}

HeartbeatService.cs

public class HeartbeatService : IDisposable
{
    private readonly HeartbeatSettings _cfg;
    private Timer _timer;
    private bool _running;

    public HeartbeatService(HeartbeatSettings cfg)
    {
        _cfg = cfg;
    }

    public void Start()
    {
        if (!_cfg.Enabled)
            return;

        _timer = new Timer(
            async _ => await ExecuteAsync(),
            null,
            TimeSpan.Zero,
            TimeSpan.FromSeconds(_cfg.IntervalSeconds));
    }

    private async Task ExecuteAsync()
    {
        if (_running) return;
        _running = true;

        try
        {
            await CheckAppAsync();
            await CheckDbAsync();
        }
        finally
        {
            _running = false;
        }
    }

    private async Task CheckAppAsync()
    {
        var time = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");

        try
        {
            using var http = new HttpClient
            {
                Timeout = TimeSpan.FromSeconds(5)
            };

            var r = await http.GetAsync(_cfg.HealthUrl);
            Log($"{time} | APP | UP | {(int)r.StatusCode}");
        }
        catch (Exception ex)
        {
            Log($"{time} | APP | DOWN | {ex.Message}");
        }
    }

    private async Task CheckDbAsync()
    {
        var time = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");

        try
        {
            using var conn = new SqlConnection(_cfg.ConnectionString);
            await conn.OpenAsync();

            using var cmd = new SqlCommand("SELECT 1", conn);
            await cmd.ExecuteScalarAsync();

            Log($"{time} | DB | UP");
        }
        catch (Exception ex)
        {
            Log($"{time} | DB | DOWN | {ex.Message}");
        }
    }

    private void Log(string msg)
    {
        Directory.CreateDirectory(Path.GetDirectoryName(_cfg.LogFile));
        File.AppendAllText(_cfg.LogFile, msg + Environment.NewLine);
    }

    public void Dispose()
    {
        _timer?.Dispose();
    }
}

HeartbeatSettings.cs

public class HeartbeatSettings
{
    public bool Enabled { get; set; }
    public int IntervalSeconds { get; set; }
    public string LogFile { get; set; }
    public string HealthUrl { get; set; }
    public string ConnectionString { get; set; }
}

Start.cs

var config = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json")
    .Build();

var settings = config.GetSection("Heartbeat").Get<HeartbeatSettings>();

using var hb = new HeartbeatService(settings);
hb.Start();

Console.ReadLine();