private async Task <bool> DispatchProjection(ProjectionDescriptor projection, MessageEnvelope envelope, ProjectingContext context)
{
while (true)
{
try
{
await TryDispatch(projection, envelope, context).NotOnCapturedContext();
return(true);
}
catch (ProjectingException ex)
{
ProjectingError(ex);
if (context.ExceptionSolution == ExceptionSolutions.Ignore)
{
return(true);
}
if (context.ExceptionSolution == ExceptionSolutions.Drop)
{
projection.Drop();
return(false);
}
if (!context.CanRetry())
{
projection.Drop();
throw;
}
context.NextRetry();
}
}
}
public ProjectingException(ProjectionDescriptor descriptor, MessageEnvelope envelope, ProjectingContext context, Exception exception)
: base($"Projecting '{descriptor.ContractName}' with message '{envelope.Meta.MessageContractName}' exception.", exception)
{
Descriptor = descriptor;
Envelope = envelope;
Context = context;
}
private DispatchingResult(ProjectionDescriptor descriptor, Statuses status, int envelopesCount, long elapsedMilliseconds, bool anyDispatched, Exception exception = null)
: this(descriptor, status)
{
EnvelopesCount = envelopesCount;
ElapsedMilliseconds = elapsedMilliseconds;
AnyDispatched = anyDispatched;
Exception = exception;
}
private async Task TryDispatch(ProjectionDescriptor descriptor, MessageEnvelope envelope, ProjectingContext context)
{
try
{
var instance = ProjectionFactory.CreateProjectionInstance(descriptor.ProjectionType);
if (instance == null)
{
throw new NullReferenceException($"Projection instance {descriptor.ProjectionType.FullName} is null.");
}
await descriptor.Invoke(instance, envelope.Message, envelope.Meta, context);
}
catch (Exception e)
{
throw new ProjectingException(descriptor, envelope, context, e);
}
}
private async Task <DispatchingResult> Dispatch(ProjectionDescriptor descriptor, List <MessageEnvelope> envelopes, CancellationToken token)
{
if (descriptor.IsDropped())
{
return(DispatchingResult.StillDropped(descriptor));
}
var sw = new Stopwatch();
var context = new ProjectingContext(MaxProjectingRetries, descriptor.Checkpoint.Position);
var anyDispatched = false;
try
{
sw.Start();
using (var scope = this.NewTransactionScope())
{
foreach (var envelope in envelopes)
{
if (!descriptor.CanDispatch(envelope.Message.GetType(), envelope.Meta.MessagePosition))
{
continue;
}
context.Reset();
if (await DispatchProjection(descriptor, envelope, context).NotOnCapturedContext())
{
descriptor.Checkpoint.Position = envelope.Meta.MessagePosition;
anyDispatched = true;
}
}
await UpdateCheckpoint(descriptor.Checkpoint, descriptor.UndropRequested, token).NotOnCapturedContext();
scope.Complete();
}
sw.Stop();
return(DispatchingResult.Dispatched(descriptor, envelopes.Count, sw.ElapsedMilliseconds, anyDispatched));
}
catch (Exception e) // error in batch
{
sw.Stop();
descriptor.Checkpoint.Position = context.StartingBatchAtPosition; // restoring position
await UpdateCheckpoint(descriptor.Checkpoint, descriptor.UndropRequested, token).NotOnCapturedContext();
return(DispatchingResult.DroppedOnException(descriptor, envelopes.Count, sw.ElapsedMilliseconds, e));
}
}
public DispatchingContext(ProjectionDescriptor descriptor, List <MessageEnvelope> envelopes)
{
Descriptor = descriptor;
Envelopes = envelopes;
}
private DispatchingResult(ProjectionDescriptor descriptor, Statuses status)
{
Descriptor = descriptor;
Status = status;
}
internal static DispatchingResult DroppedOnException(ProjectionDescriptor descriptor, int envelopesCount, long elapsedMilliseconds, Exception exception)
{
return(new DispatchingResult(descriptor, Statuses.DroppedOnException, envelopesCount, elapsedMilliseconds, false, exception));
}
internal static DispatchingResult Dispatched(ProjectionDescriptor descriptor, int envelopesCount, long elapsedMilliseconds, bool anyDispatched)
{
return(new DispatchingResult(descriptor, Statuses.Dispatched, envelopesCount, elapsedMilliseconds, anyDispatched));
}
internal static DispatchingResult StillDropped(ProjectionDescriptor descriptor) => new DispatchingResult(descriptor, Statuses.StillDropped);
