Bugs in the way Notifiers use WebClients

[WichardRiezebos]

2016-10-18 13:36:53,648 [98] ERROR OmniaMonitoring - App tick caused a NotificationException.
Nimator.NotificationException: One or more notifiers could not notify. ---> System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
   at System.Net.ScatterGatherBuffers.AllocateMemoryChunk(Int32 newSize)
   at System.Net.ScatterGatherBuffers..ctor(Int64 totalSize)
   at System.Net.WebClient.DownloadBitsState.SetResponse(WebResponse response)
   at System.Net.WebClient.DownloadBits(WebRequest request, Stream writeStream, CompletionDelegate completionDelegate, AsyncOperation asyncOp)
   at System.Net.WebClient.UploadDataInternal(Uri address, String method, Byte[] data, WebRequest& request)
   at System.Net.WebClient.UploadString(Uri address, String method, String data)
   at System.Net.WebClient.UploadString(String address, String data)
   at Nimator.Util.SimpleRestUtils.PostToRestApiInternal(String url, Object message) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Util\SimpleRestUtils.cs:line 24
   at Nimator.Notifiers.OpsGenieNotifier.SendHeartbeat() in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Notifiers\OpsGenieNotifier.cs:line 37
   at Nimator.Notifiers.OpsGenieNotifier.Notify(INimatorResult result) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Notifiers\OpsGenieNotifier.cs:line 27
   at Nimator.Nimator.<>c__DisplayClass4_0.<Tick>b__0(INotifier notifier) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Nimator.cs:line 82
   --- End of inner exception stack trace ---
   at Nimator.Nimator.Tick() in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Nimator.cs:line 92
   at Nimator.Nimator.TickSafe(ILog logger) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Nimator.cs:line 51
---> (Inner Exception #0) System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
   at System.Net.ScatterGatherBuffers.AllocateMemoryChunk(Int32 newSize)
   at System.Net.ScatterGatherBuffers..ctor(Int64 totalSize)
   at System.Net.WebClient.DownloadBitsState.SetResponse(WebResponse response)
   at System.Net.WebClient.DownloadBits(WebRequest request, Stream writeStream, CompletionDelegate completionDelegate, AsyncOperation asyncOp)
   at System.Net.WebClient.UploadDataInternal(Uri address, String method, Byte[] data, WebRequest& request)
   at System.Net.WebClient.UploadString(Uri address, String method, String data)
   at System.Net.WebClient.UploadString(String address, String data)
   at Nimator.Util.SimpleRestUtils.PostToRestApiInternal(String url, Object message) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Util\SimpleRestUtils.cs:line 24
   at Nimator.Notifiers.OpsGenieNotifier.SendHeartbeat() in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Notifiers\OpsGenieNotifier.cs:line 37
   at Nimator.Notifiers.OpsGenieNotifier.Notify(INimatorResult result) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Notifiers\OpsGenieNotifier.cs:line 27
   at Nimator.Nimator.<>c__DisplayClass4_0.<Tick>b__0(INotifier notifier) in D:\buildAgent\work\a39b915f9d70f079\src\Nimator\Nimator.cs:line 82<---

Nimator uses simple WebClient's in the SimpleRestUtils.cs file, which has two problems:

• the default timeout is kind of big (should e.g. OpsGenie or Slack not be available), 1 minute I believe, this can easily be 5 or 10 seconds, tops
• you might want to turn AllowWriteStreamBuffering to false, see: https://bytes.com/topic/c-sharp/answers/255250-system-net-scattergatherbuffers-memorychuck-allocates-large-byte

public class CustomWebClient : WebClient
{
    private readonly TimeSpan timeout;

    public CustomWebClient(TimeSpan timeout)
    {
        this.timeout = timeout;
    }

    protected override WebRequest GetWebRequest(Uri address)
    {
        HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);

        request.Timeout = (int)this.timeout.TotalMilliseconds;
        request.AllowWriteStreamBuffering = false;

        return request;
    }
}