I have 2 system which can communicate through API each other.
Here is my code
System A:
using (var transaction = new TransactionScope())
{
var myBook = _bookRepository.Table.FirstOrDefault(x => x.Id == request.bookID);
myBook.AssigneeId = null;
_bookRepository.Update(ticket);
var result = await _anotherBApi.ApproveBookAsync(request.bookID);
if (result.ShStatus != ResponseStatus.Success)
{
result.ErrorType = ErrorType.Error;
return result;
}
transaction.Complete();
}
Function ApproveBookAsync(request.bookID) will call to B system's API. After handling, B system call back A system's API to update Book's information (the same the one above).
Above my code. I cannot transaction.Complete(); because when B system call A system's API it will create new transaction.
Expect: I want to handle step by step as:
Update new information for a Book instance (sample ID = 1)
Call to B system's API (after B system also call A system's A to update Book ID = 1)
When call B system fail, I want to rollback all changes before. If success, commit.
When using async/await in TransactionScope block, you need to opt that you need your transaction to flow accross thread continuations like this:
using (var transaction = new TransactionScope(TransactionScopeAsyncFlowOption.Enabled))
{
// Your code that contains some calls to async method.
transaction.Complete();
}
Related
I am working in a Service Fabric application that uses IReliableQueue. For the uses cases of this system, the IReliableConcurrentQueue makes sense to use and some local testing (i.e. basically by just changing the code to use IReliableConcurrentQueue instead of IReliableQueue - queue name does not change) shows great performance improvements. However, I am worried about the impact of changing this in a production system (i.e. upgrading). I can't find any docs or online questions (unless I just missed them) about these considerations. For example, in this system, the existing IReliableQueue will almost always have items. So what happens to that data when I upgrade the SF application? Will it be available to dequeue in the IReliableConcurrentQueue? Or would data be lost? I know I can "just try it" but wanted to see if someone out there had done the same or could offer pointers to existing resources. Thanks!
Sorry for a late answer (that you probably don't need anymore but still).
When we calling GetOrAddAsync method on IReliableStateManager we aren't retrieving the interface to store values - we actually creating an instance of reliable collection. This basically means that type of the interface we specify is very important.
Taking this into account if we do this:
Service v. 1.0
// Somewhere in RunAsync for example
await this.StateManager.GetOrAddAsync<IReliableQueue<long>>("MyCollection")
Then doing this in the next version:
Service v. 1.1
// Somewhere in RunAsync for example
await this.StateManager.GetOrAddAsync<IReliableConcurrentQueue<long>>("MyCollection")
will throw an exception:
Returned reliable object of type Microsoft.ServiceFabric.Data.Collections.DistributedQueue`1[System.Int64] cannot be casted to requested type Microsoft.ServiceFabric.Data.Collections.IReliableConcurrentQueue`1[System.Int64]
and then:
System.ExecutionEngineException: 'Exception of type 'System.ExecutionEngineException' was thrown.'
The above exception looks like a bug so I have filled one.
UPDATE 2019.06.28
It turned out that appearance of System.ExecutionEngineException isn't a bug but rather an undocumented behavior of Environment.FailFast method in combination with Visual Studio debugger.
Please see my comment to the above issue.
This is what would happen.
There are plenty ways to overcome this.
Here is the most obvious one:
Example
var migrate = false; // This flag indicates whether the migration was already done.
var migrateValues = new List<long>();
var applicationFlags = await this.StateManager
.GetOrAddAsync<IReliableDictionary<string, bool>>("application-flags");
using (var transaction = this.StateManager.CreateTransaction())
{
var flag = await applicationFlags
.TryGetValueAsync(transaction, "queue-to-concurrent-queue-migration");
if (!flag.HasValue || !flag.Value)
{
var queue = await this.StateManager
.GetOrAddAsync<IReliableQueue<long>>("value-collection");
for (;;)
{
var c = await queue.TryDequeueAsync(transaction);
if (!c.HasValue)
{
break;
}
migrateValues.Add(c.Value);
}
migrate = true;
}
}
if (migrate)
{
await this.StateManager.RemoveAsync("value-collection");
using (var transaction = this.StateManager.CreateTransaction())
{
var concurrentQueue = await this.StateManager
.GetOrAddAsync<IReliableConcurrentQueue<long>>("value-collection");
foreach (var i in migrateValues)
{
await concurrentQueue.EnqueueAsync(transaction, i);
}
await applicationFlags.AddOrUpdateAsync(
transaction,
"queue-to-concurrent-queue-migration",
true,
(s, b) => true);
}
await transaction.CommitAsync();
}
Please note that this code is just an illustrative example and should be properly tested before applying it to real life application.
Entity Framework: 6.1.3.
I have a function that reads a simple table for a record and either updates it or first creates a new entity. Either way it then calls AddOrUpdate and SaveChangesAsync. This function has worked for quite some time without any apparent problem.
In my current situation, however, I'm getting a return value of 0 from SaveChangesAsync. I have a break point just before the save and verified that the record doesn't exist. I step through the code and, as expected, a new entity was created. The curious part is that the record is now in the table as desired. If I understand the documentation, 0 should indicate that nothing was written out.
I'm not using transactions for this operation. Other database operations including writes would have already occurred on the context prior to this function being called, however, they should all have been committed.
So how can I get a return of 0 and still have something written out?
Here is a slightly reduced code fragment:
var settings = OrganizationDb.Settings;
var setting = await settings.FirstOrDefaultAsync(x => x.KeyName == key).ConfigureAwait(false);
if (setting == null)
{
setting = new Setting()
{
KeyName = key,
};
}
setting.Value = value;
settings.AddOrUpdate(setting);
if (await OrganizationDb.SaveChangesAsync().ConfigureAwait(false) == 0)
{
//// error handling - record not written out.
}
I have the following Scenario:
I have 2 web api functions, which delete / insert data into a SQL Server database. The data Access is handled via .net entityframework v6. The insert / delete methods were only called from a local running c# program. I am using HttpClient class to call the web api methods. The web methods works as follows, when I call insert all existing records will be deleted and the new ones will be inserted, so there is no real update process.
Here are my 2 functions:
[HttpDelete()]
public async Task<int> DeleteStartlist(int eventid, int run, int heat, string category)
{
_data.dbsStartlistEntries.RemoveRange(_data.dbsStartlistEntries.Where(s => s.Event.Id == eventid && s.RoundOrder == run && s.HeatOrder == heat && s.Category == category));
return await _data.SaveChangesAsync();
}
[HttpPost()]
public async Task<int> UpdateStartlists(int eventid, List<StartlistEntry> en)
{
try
{
if (en.Count == 0)
return 0;
var xdel = await DeleteStartlist(eventid, en[0].RoundOrder, en[0].HeatOrder, en[0].Category);
var ev = await _data.dbsEvents.FindAsync(eventid);
if (ev != null)
{
en.ForEach(e => e.Event = ev);
_data.dbsStartlistEntries.AddRange(en);
}
return await _data.SaveChangesAsync();
}
catch (System.Exception ex)
{
return 1;
}
}
But now I have the following Problem. For example when I call the Update Method 10 times in a row without waiting between the function calls I receive following exception:
Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.
For me this sounds like a concurrency Problem, but I do not really know how to solve it.
So here is my question, is there a way to let the api calls wait for each other server side, or are they always running concurrent or is there a way to lock the database?
We have two different query strategies that we'd ideally like to operate in conjunction on our site without opening redundant connections. One strategy uses the enterprise library to pull Database objects and Execute_____(DbCommand)s on the Database, without directly selecting any sort of connection. Effectively like this:
Database db = DatabaseFactory.CreateDatabase();
DbCommand q = db.GetStoredProcCommand("SomeProc");
using (IDataReader r = db.ExecuteReader(q))
{
List<RecordType> rv = new List<RecordType>();
while (r.Read())
{
rv.Add(RecordType.CreateFromReader(r));
}
return rv;
}
The other, newer strategy, uses a library that asks for an IDbConnection, which it Close()es immediately after execution. So, we do something like this:
DbConnection c = DatabaseFactory.CreateDatabase().CreateConnection();
using (QueryBuilder qb = new QueryBuilder(c))
{
return qb.Find<RecordType>(ConditionCollection);
}
But, the connection returned by CreateConnection() isn't the same one used by the Database.ExecuteReader(), which is apparently left open between queries. So, when we call a data access method using the new strategy after one using the old strategy inside a TransactionScope, it causes unnecessary promotion -- promotion that I'm not sure we have the ability to configure for (we don't have administrative access to the SQL Server).
Before we go down the path of modifying the query-builder-library to work with the Enterprise Library's Database objects ... Is there a way to retrieve, if existent, the open connection last used by one of the Database.Execute_______() methods?
Yes, you can get the connection associated with a transaction. Enterprise Library internally manages a collection of transactions and the associated database connections so if you are in a transaction you can retrieve the connection associated with a database using the static TransactionScopeConnections.GetConnection method:
using (var scope = new TransactionScope())
{
IEnumerable<RecordType> records = GetRecordTypes();
Database db = DatabaseFactory.CreateDatabase();
DbConnection connection = TransactionScopeConnections.GetConnection(db).Connection;
}
public static IEnumerable<RecordType> GetRecordTypes()
{
Database db = DatabaseFactory.CreateDatabase();
DbCommand q = db.GetStoredProcCommand("GetLogEntries");
using (IDataReader r = db.ExecuteReader(q))
{
List<RecordType> rv = new List<RecordType>();
while (r.Read())
{
rv.Add(RecordType.CreateFromReader(r));
}
return rv;
}
}
I need to save to two different databases after some user action. Currently, I have the following:
using (EFEntities1 dc = new EFEntities1())
{
dc.USERS.Add(user);
dc.SaveChanges();
}
using (EFEntities2 dc = new EFEntities2())
{
dc.USERS.Add(user);
dc.SaveChanges();
}
These are two separate code blocks within the same method, so I believe if the second one fails, the first one won't rollback. How do I make sure both transactions rollback if something fails?
You can wrap them in a TransactionScope. Note that this will probably call the DTC.
using (TransactionScope scope = new TransactionScope())
{
using (EFEntities1 dc = new EFEntities1())
{
dc.USERS.Add(user);
dc.SaveChanges();
}
using (EFEntities2 dc = new EFEntities2())
{
dc.USERS.Add(user);
dc.SaveChanges();
}
scope.complete();
}