/// <summary>
/// Orchestrates an Http/s call to a remote service pointed to by a set of EndpointAssigment objects.
/// This algorithm provides fail-over and circuit breaker functionality built-in.
/// An actual call is performed in a passed-in call body functor.
/// </summary>
/// <typeparam name="TResult">The resulting type of the call, as obtained from call body</typeparam>
/// <param name="assignments">An enumerable of hosts to be tried in sequence. The subsequent host are tried in case of failure</param>
/// <param name="body">Call body functor. May not be null</param>
/// <param name="cancellation">Optional CancellationToken</param>
/// <returns>TResult call result or throws `ClientException` if call eventually failed after all fail-overs tried</returns>
public static async Task <TResult> Call <TResult>(this IEnumerable <EndpointAssignment> assignments,
Func <IHttpTransport, CancellationToken?, Task <TResult> > body,
CancellationToken?cancellation = null)
{
body.NonNull(nameof(body));
var first = assignments.NonNull(nameof(assignments)).FirstOrDefault();
if (!first.IsAssigned)
{
throw new ClientException(StringConsts.HTTP_CLIENT_CALL_ASSIGMENT_ERROR.Args("No assignments provided"));
}
var service = first.Endpoint.Service as IHttpService;
if (service == null)
{
throw new ClientException(StringConsts.HTTP_CLIENT_CALL_ASSIGMENT_ERROR.Args("Wrong service type assignments"));
}
if (!assignments.All(a => a.Endpoint.Service == service &&
a.MappedContract == first.MappedContract &&
a.MappedRemoteAddress == first.MappedRemoteAddress &&
a.Endpoint.Network == first.Endpoint.Network &&
a.Endpoint.Binding == first.Endpoint.Binding))
{
throw new ClientException(StringConsts.HTTP_CLIENT_CALL_ASSIGMENT_ERROR.Args("Inconsistent endpoint assignments"));
}
var tries = 0;
List <Exception> errors = null;
foreach (var assigned in assignments)
{
if (!assigned.Endpoint.IsAvailable)
{
continue; //offline or Circuit tripped todo: instrument
}
tries++;
var ep = assigned.Endpoint as IEndpointImplementation;
var transport = service.AcquireTransport(assigned);
try
{
var http = (transport as IHttpTransport).NonNull("Implementation error: cast to IHttpTransport");
var result = await body(http, cancellation).ConfigureAwait(false);
CallGuardException.Protect(ep, _ => _.NotifyCallSuccess(transport));
return(result);
}
catch (Exception error)
{
//Implementation error
if (error is CallGuardException)
{
throw;
}
//TaskCanceledException gets thrown on simple timeout even when cancellation was NOT requested
if (error is TaskCanceledException && cancellation.HasValue && cancellation.Value.IsCancellationRequested)
{
throw;
}
var errorClass = ep.NotifyCallError(transport, error);
//todo instrument
if (errorClass == CallErrorClass.ServiceLogic)
{
throw; //throw logical errors
}
if (errors == null)
{
errors = new List <Exception>();
}
errors.Add(error);
}
finally
{
service.ReleaseTransport(transport);
}
}//foreach
var toThrow = new ClientException(StringConsts.HTTP_CLIENT_CALL_FAILED.Args(service.GetType().Name, first.MappedRemoteAddress.TakeLastChars(32, "..."), tries),
errors != null ? new AggregateException(errors) :
new AggregateException("No inner errors"));
if (service.ComponentEffectiveLogLevel <= Log.MessageType.Error)
{
service.App.Log.Write(
new Log.Message
{
Topic = service.ComponentLogTopic,
Type = Log.MessageType.Error,
From = "{0}{1}.{2}".Args(service.ComponentLogFromPrefix, nameof(HttpCallExtensions), nameof(Call)),
Text = "Service `{0}` call error: {1}".Args(service.Name, toThrow.ToMessageWithType()),
Exception = toThrow,
RelatedTo = (Ambient.CurrentCallFlow?.ID) ?? Guid.Empty
});
}
throw toThrow;
}
/// <summary>
/// Performs a Http/s call to a remote service pointed to by a EndpointAssigment object.
/// An actual call is performed in a passed-in call body functor.
/// </summary>
/// <typeparam name="TResult">The resulting type of the call, as obtained from call body</typeparam>
/// <param name="assignment">An endpoint assignment to call</param>
/// <param name="body">Call body functor. May not be null</param>
/// <param name="cancellation">Optional CancellationToken</param>
/// <returns>TResult call result or throws `ClientException` if call failed </returns>
public static async Task <TResult> CallOne <TResult>(this EndpointAssignment assignment,
Func <IHttpTransport, CancellationToken?, Task <TResult> > body,
CancellationToken?cancellation = null)
{
body.NonNull(nameof(body));
if (!assignment.IsAssigned)
{
throw new ClientException(StringConsts.HTTP_CLIENT_CALL_ASSIGMENT_ERROR.Args("No assignments provided"));
}
var service = assignment.Endpoint.Service as IHttpService;
if (service == null)
{
throw new ClientException(StringConsts.HTTP_CLIENT_CALL_ASSIGMENT_ERROR.Args("Wrong service type assignments"));
}
Exception cause = null;
if (assignment.Endpoint.IsAvailable)
{
var ep = assignment.Endpoint as IEndpointImplementation;
var transport = service.AcquireTransport(assignment);
try
{
var http = (transport as IHttpTransport).NonNull("Implementation error: cast to IHttpTransport");
var result = await body(http, cancellation).ConfigureAwait(false);
CallGuardException.Protect(ep, _ => _.NotifyCallSuccess(transport));
return(result);
}
catch (Exception error)
{
//Implementation error
if (error is CallGuardException)
{
throw;
}
//TaskCanceledException gets thrown on simple timeout even when cancellation was NOT requested
if (error is TaskCanceledException && cancellation.HasValue && cancellation.Value.IsCancellationRequested)
{
throw;
}
var errorClass = ep.NotifyCallError(transport, error);
//todo instrument
if (errorClass == CallErrorClass.ServiceLogic)
{
throw; //throw logical errors
}
cause = error;
}
finally
{
service.ReleaseTransport(transport);
}
}
else
{
cause = new ClientException("Endpoint !Available");
}
var toThrow = new ClientException(StringConsts.HTTP_CLIENT_CALL_FAILED
.Args(service.GetType().Name,
assignment.MappedRemoteAddress.TakeLastChars(32, "..."),
1),
cause);
if (service.ComponentEffectiveLogLevel <= Log.MessageType.Error)
{
service.App.Log.Write(
new Log.Message
{
Topic = service.ComponentLogTopic,
Type = Log.MessageType.Error,
From = "{0}{1}.{2}".Args(service.ComponentLogFromPrefix, nameof(HttpCallExtensions), nameof(Call)),
Text = "Service `{0}` call error: {1}".Args(service.Name, toThrow.ToMessageWithType()),
Exception = toThrow,
RelatedTo = (Ambient.CurrentCallFlow?.ID) ?? Guid.Empty
});
}
throw toThrow;
}//CallOne