private void StartLoop(IScheduler scheduler)
{
//delegate allocations below - but that's fine as it's not really on the "critical path" (polled relatively infrequently) - and it's much more readable this way
scheduler.Schedule(repeatAction => _httpListener.BeginGetContext(ar =>
{
try
{
var httpListenerContext = _httpListener.EndGetContext(ar);
var request = httpListenerContext.Request;
var response = httpListenerContext.Response;
response.StatusCode = 200;
var acceptHeader = request.Headers.Get("Accept");
var acceptHeaders = acceptHeader == null ? null : acceptHeader.Split(',');
var contentType = ScrapeHandler.GetContentType(acceptHeaders);
response.ContentType = contentType;
using (var outputStream = response.OutputStream)
{
var collected = _registry.CollectAll();
ScrapeHandler.ProcessScrapeRequest(collected, contentType, outputStream);
}
response.Close();
}
catch (Exception e)
{
Trace.WriteLine(string.Format("Error in MetricsServer: {0}", e));
}
repeatAction.Invoke();
}, null));
}
public void Configure(IApplicationBuilder app)
{
app.Run(context => {
var response = context.Response;
var request = context.Request;
response.StatusCode = 200;
var acceptHeader = request.Headers["Accept"];
var contentType = ScrapeHandler.GetContentType(acceptHeader);
response.ContentType = contentType;
using (var outputStream = response.Body) {
var collected = _registry.CollectAll();
ScrapeHandler.ProcessScrapeRequest(collected, contentType, outputStream);
};
return(Task.FromResult(true));
});
}
public async Task Invoke(HttpContext context)
{
// We just handle the root URL (/metrics or whatnot).
if (!string.IsNullOrWhiteSpace(context.Request.Path.Value))
{
await _next(context);
return;
}
var request = context.Request;
var response = context.Response;
var acceptHeaders = request.Headers["Accept"];
var contentType = ScrapeHandler.GetContentType(acceptHeaders);
response.ContentType = contentType;
IEnumerable <MetricFamily> metrics;
try
{
metrics = _registry.CollectAll();
}
catch (ScrapeFailedException ex)
{
response.StatusCode = 503;
if (!string.IsNullOrWhiteSpace(ex.Message))
{
using (var writer = new StreamWriter(response.Body))
await writer.WriteAsync(ex.Message);
}
return;
}
response.StatusCode = 200;
using (var outputStream = response.Body)
ScrapeHandler.ProcessScrapeRequest(metrics, contentType, outputStream);
}
protected override Task StartServer(CancellationToken cancel)
{
// This will ensure that any failures to start are nicely thrown from StartServerAsync.
_httpListener.Start();
// Kick off the actual processing to a new thread and return a Task for the processing thread.
return(Task.Factory.StartNew(delegate
{
try
{
while (!cancel.IsCancellationRequested)
{
// There is no way to give a CancellationToken to GCA() so, we need to hack around it a bit.
var getContext = _httpListener.GetContextAsync();
getContext.Wait(cancel);
var context = getContext.Result;
var request = context.Request;
var response = context.Response;
try
{
IEnumerable <MetricFamily> metrics;
try
{
metrics = _registry.CollectAll();
}
catch (ScrapeFailedException ex)
{
response.StatusCode = 503;
if (!string.IsNullOrWhiteSpace(ex.Message))
{
using (var writer = new StreamWriter(response.OutputStream))
writer.Write(ex.Message);
}
continue;
}
var acceptHeader = request.Headers.Get("Accept");
var acceptHeaders = acceptHeader?.Split(',');
var contentType = ScrapeHandler.GetContentType(acceptHeaders);
response.ContentType = contentType;
response.StatusCode = 200;
using (var outputStream = response.OutputStream)
ScrapeHandler.ProcessScrapeRequest(metrics, contentType, outputStream);
}
catch (Exception ex) when(!(ex is OperationCanceledException))
{
Trace.WriteLine(string.Format("Error in MetricsServer: {0}", ex));
try
{
response.StatusCode = 500;
}
catch
{
// Might be too late in request processing to set response code, so just ignore.
}
}
finally
{
response.Close();
}
}
}
finally
{
_httpListener.Stop();
_httpListener.Close();
}
}, TaskCreationOptions.LongRunning));
}
