/// <summary>
/// Processes the incoming HTTP call and capture details about
/// the request, the response, the identity of the caller and the
/// call duration to persistent storage.
/// </summary>
/// <param name="context">A reference to the Owin context.</param>
/// <returns />
public override async Task Invoke(IOwinContext context)
{
var request = context.Request;
var response = context.Response;
// capture details about the caller identity
var identity =
request.User != null && request.User.Identity.IsAuthenticated ?
request.User.Identity.Name :
"(anonymous)"
;
var record = new HttpEntry
{
CallerIdentity = identity,
};
// replace the request stream in order to intercept downstream reads
var requestBuffer = new MemoryStream();
var requestStream = new ContentStream(requestBuffer, request.Body);
request.Body = requestStream;
// replace the response stream in order to intercept downstream writes
var responseBuffer = new MemoryStream();
var responseStream = new ContentStream(responseBuffer, response.Body);
response.Body = responseStream;
// add the "Http-Tracking-Id" response header
context.Response.OnSendingHeaders(state =>
{
var ctx = state as IOwinContext;
if (ctx == null) return;
var resp = ctx.Response;
// adding the tracking id response header so that the user
// of the API can correlate the call back to this entry
//resp.Headers.Add(_trackingIdPropertyName, new[] { record.LoggingId.ToString("d"), });
}, context);
// invoke the next middleware in the pipeline
await Next.Invoke(context);
// rewind the request and response buffers
// and record their content
WriteRequestHeaders(request, record);
record.RequestLength = requestStream.ContentLength;
record.Request = await WriteContentAsync(requestStream, record.RequestHeaders, _maxRequestLength);
WriteResponseHeaders(response, record);
record.ResponseLength = responseStream.ContentLength;
record.Response = await WriteContentAsync(responseStream, record.ResponseHeaders, _maxResponseLength);
// persist details of the call to durable storage
await HttpLoggingStore.InsertRecordAsync(record);
}
private static async Task<string> WriteContentAsync(ContentStream stream, IDictionary<string, string[]> headers, long maxLength)
{
var contentType =
headers.ContainsKey(ContentType) ?
headers[ContentType][0] :
null
;
return await stream.ReadContentAsync(contentType, maxLength);
}
