What's wrong on using HttpWebRequest this way? - azure

Question

This is the way I do server request to some endpoints from Azure:
public T SingleRead<T>(string url, string method, object entity = null)
{
T returnValue = default(T);
var resp = GetRESTResponse(url, method, entity);
string responseText = GetResponseText(resp);
try
{
returnValue = JsonConvert.DeserializeObject<T>(responseText);
}
catch (Exception ex)
{
return default(T);
}
return returnValue;
}
private HttpWebResponse GetRESTResponse(string url, string method, object entity = null)
{
var address;
if (!url.StartsWith("http"))
{
if (!url.StartsWith("/")) url = $"/{url}";
address = baseAddress + url;
}
else
{
address = url;
}
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(address);
req.Method = method;
if (entity != null)
{
byte[] byteArray = Encoding.Default.GetBytes(JsonConvert.SerializeObject(entity));
req.ContentLength = byteArray.Length;
req.ContentType = "application/json";
Stream dataStream = req.GetRequestStream();
dataStream.Write(byteArray, 0, byteArray.Length);
dataStream.Flush();
dataStream.Close();
}
HttpWebResponse resp;
try
{
resp = (HttpWebResponse)req.GetResponse();
}
catch (WebException e)
{
Log(e.Reponse);
resp = (HttpWebResponse)e.Response;
}
return resp;
}
private static string GetResponseText(HttpWebResponse resp)
{
var encoding = Encoding.ASCII;
string responseText = ".";
using (var reader = new StreamReader(resp.GetResponseStream(), encoding))
{
responseText = reader.ReadToEnd();
}
if (resp.StatusCode == HttpStatusCode.InternalServerError || resp.StatusCode == HttpStatusCode.BadRequest || resp.StatusCode == HttpStatusCode.NotFound)
{
return "";
}
return responseText;
}
It works quite often. Sometimes, it doesn't, and I get the a "A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond" error from the Log.
Is there some wrong in the procedure, or it could be a "timeout" by endpoint?
The called server users says "we don't have any problem, and we don't get the request".
Not sure if its the fault of the code above (maybe some stream not closed?). But I don't see any problem. Do you see any trouble in this?

Answer 1

It can be a network issue, which fails quite often. You need to remember there are several switches until the request goes outside the datacenter, and there are countless requests happening at the same time (you, and all other Azure customers).
This can be a transient fault, which may work if you send another request. You need to implement some retry logic to identify if the failure is transient or not.
More info:
https://learn.microsoft.com/en-us/azure/architecture/patterns/retry
And here's a sample using Polly, which is strongly recommended and even used inside Azure SDKs:
https://stackoverflow.com/a/66554740/1384539
https://learn.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/implement-http-call-retries-exponential-backoff-polly
https://github.com/App-vNext/Polly