public async Task PersistAsync(T model)
{
var persistedObject = await RetrieveInternalAsync(model.Key);
if (persistedObject == null)
{
await _db.CreateDocumentAsync(new PersistedModel <T>(model));
}
else
{
persistedObject.Current = model;
await _db.UpdateDocumentAsync(persistedObject);
}
}
public async Task PersistAsync(TModel model)
{
//waits untill the previous task has been finished (sort of like a lock but no 100% the same)
await _persistMutex.WaitAsync().ConfigureAwait(false);
try
{
var persistedObject = RetrieveInternal(model.Key);
if (persistedObject == null)
{
SetETag(model);
await _db.CreateDocumentAsync(new PersistedModel <TModel>(model));
//Try catch to handle transaction logic
try
{
await EventSourcingCreateRecordAsync(null, model);
}
catch
{
//Revert the creation of the documentDb doc
await DeleteAsync(model.Key, false);
throw;
}
}
else
{
//When doing a patch, the last one wins since we are only updating a part of the object and probably do not have access to the etag.
//To detect a patch operation, check the e-tag for a null value
if (persistedObject.Current.ETag != null && persistedObject.Current.ETag != model.ETag)
{
throw new Exception("The object has changed between your read action and this update request. We cannot continue with the save.");
}
SetETag(model);
//It's important that this happens before the persistedObject.Current is set to the updated model to get the diff...
var newEventSourcingRecord = await EventSourcingCreateRecordAsync(persistedObject.Current, model);
try
{
persistedObject.Current = model;
await _db.UpdateDocumentAsync(persistedObject);
}
catch
{
//Revert the creation of the event sourcing record
//var entityToDelete = await TableStorage.GetSingleEntity<ITableEntity>(newEventSourcingRecord.PartitionKey, newEventSourcingRecord.RowKey);
await _tableStorage.DeleteAsync(newEventSourcingRecord);
throw;
}
}
}
finally
{
_persistMutex.Release();
}
}