MalwareMultiScan/MalwareMultiScan.Scanner/Services/ConsulHostedService.cs

using System;
using System.Collections.Generic;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
using Consul;
using MalwareMultiScan.Backends.Backends.Interfaces;
using Microsoft.Extensions.Hosting;

namespace MalwareMultiScan.Scanner.Services
{
    /// <summary>
    /// Consul registration hosted service.
    /// </summary>
    public class ConsulHostedService : BackgroundService
    {
        private static readonly string ServiceId = Dns.GetHostName();
        private static readonly string CheckId = $"ttl-{ServiceId}";

        private readonly IConsulClient _consulClient;
        private readonly AgentServiceRegistration _registration;
        
        /// <summary>
        /// Initialize consul hosted service.
        /// </summary>
        /// <param name="consulClient">Consul client.</param>
        /// <param name="scanBackend">Scan backend.</param>
        public ConsulHostedService(
            IConsulClient consulClient,
            IScanBackend scanBackend)
        {
            _consulClient = consulClient;

            _registration = new AgentServiceRegistration
            {
                ID = ServiceId,
                Name = "scanner",

                Meta = new Dictionary<string, string>
                {
                    {"BackendId", scanBackend.Id}
                }
            };
        }

        /// <inheritdoc />
        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                await _consulClient.Agent.PassTTL(
                    CheckId, string.Empty, stoppingToken);

                await Task.Delay(TimeSpan.FromSeconds(5), stoppingToken);
            }
        }

        /// <inheritdoc />
        public override async Task StartAsync(CancellationToken cancellationToken)
        {
            await _consulClient.Agent.ServiceDeregister(
                _registration.ID, cancellationToken);

            await _consulClient.Agent.ServiceRegister(
                _registration, cancellationToken);

            await _consulClient.Agent.CheckRegister(new AgentCheckRegistration
            {
                ID = CheckId,
                Name = "TTL",
                ServiceID = ServiceId,
                TTL = TimeSpan.FromSeconds(15),
                DeregisterCriticalServiceAfter = TimeSpan.FromSeconds(60)
            }, cancellationToken);

            await base.StartAsync(cancellationToken);
        }

        /// <inheritdoc />
        public override async Task StopAsync(CancellationToken cancellationToken)
        {
            await _consulClient.Agent.ServiceDeregister(
                _registration.ID, cancellationToken);

            await _consulClient.Agent.CheckDeregister(
                CheckId, cancellationToken);

            await base.StopAsync(cancellationToken);
        }
    }
}