Fixed DNS slow request; added DNS timeout option

backend/SiteStatus/SiteStatus/Business/DnsBusiness.cs

 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
-using System.Runtime.CompilerServices;
+using System.Threading;
 using System.Threading.Tasks;
 using ARSoft.Tools.Net.Dns;
 using Microsoft.Extensions.Options;
                 ServerStatus = new List<DnsZoneServerStatusDbo>()
             };
 
+            var cancellationTokenSource = new CancellationTokenSource();
             var list = new List<KeyValuePair<string, Task<List<SoaRecord>>>>();
             var tasks = new List<Task<List<SoaRecord>>>();
             foreach (var server in servers)
                 try
                 {
                     var resolver = new DnsStubResolver(new []{IPAddress.Parse(server)});
-                    var recordsTask = resolver.ResolveAsync<SoaRecord>(zone, RecordType.Soa);
+                    var recordsTask = resolver.ResolveAsync<SoaRecord>(zone, RecordType.Soa, RecordClass.INet, cancellationTokenSource.Token);
                     list.Add(new KeyValuePair<string, Task<List<SoaRecord>>>(server, recordsTask));
                     tasks.Add(recordsTask);
                 }
-                catch (Exception e)
+                catch (Exception)
                 {
                     tasks.Add(Task.FromResult<List<SoaRecord>>(null));
                 }
             }
 
-            await Task.WhenAll(tasks.ToArray());
+            try
+            {
+                var allTasks = Task.WhenAll(tasks.ToArray());
+                if (await Task.WhenAny(allTasks, Task.Delay(Options.Dns.Resolve.Timeout)) == allTasks) {
+                    await allTasks;
+                } else {
+                    cancellationTokenSource.Cancel();
+                }
+            }
+            catch (Exception)
+            {
+                // Ignore, errors will be handled later
+            }
 
             foreach (var recordResult in list)
             {
                         Soa = record?.ToString()
                     });
                 }
-                catch (Exception e)
+                catch (Exception)
                 {
                     dnsStatus.ServerStatus.Add(new DnsZoneServerStatusDbo
                     {
 
         public DnsStatusDbo GetDnsStatus()
         {
-            var status = new DnsStatusDbo
+            var allTasks = new Dictionary<SettingsDnsViewDbo, IList<Task<DnsZoneStatusDbo>>>();
+            foreach (var view in Options.Dns.Views)
             {
-                Views = Options.Dns.Views.Select(view =>
-                {
-                    var servers = view.Servers.Select(server => server.Ip).ToList();
-                    var tasks = view.Zones.Select(zone => GetZoneStatusAsync(zone.Name, servers)).ToArray();
+                var servers = view.Servers.Select(server => server.Ip).ToList();
+                var tasks = view.Zones.Select(zone => GetZoneStatusAsync(zone.Name, servers)).ToArray();
+
+                allTasks.Add(view, tasks);
+            }
 
-                    Task.WaitAll(tasks);
+            Task.WaitAll(allTasks.SelectMany(x => x.Value).ToArray());
 
-                    var results = tasks.Select(task => task.Result).ToList();
+            var status = new DnsStatusDbo
+            {
+                Views = allTasks.Select(pair =>
+                {
+                    var results = pair.Value.Select(task => task.Result).ToList();
 
                     return new DnsStatusViewDbo
                     {
-                        Name = view.Name,
+                        Name = pair.Key.Name,
                         Zones = results
                     };
                 }).ToList()

backend/SiteStatus/SiteStatus/Dbo/SettingsDnsDbo.cs

 {
     public class SettingsDnsDbo
     {
+        public SettingsDnsResolveDbo Resolve { get; set; }
+
         public IList<SettingsDnsViewDbo> Views { get; set; }
     }
 }

backend/SiteStatus/SiteStatus/Dbo/SettingsDnsResolveDbo.cs

+namespace SiteStatus.Dbo
+{
+    public class SettingsDnsResolveDbo
+    {
+        public int Timeout { get; set; }
+    }
+}