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();
}
Related
We have two .net services (.Net core console applications) which are accessing a postgres db table.
Service 1 inserts some 500 rows every 1 minute. It runs as a background thread.
Service 2 reads data from the same table continuously. There is an MQTT publisher which keeps reading data from this table when any new data is requested. This also happens very frequently i.e atleast 4/5 times a minute.
We are getting "FATAL: sorry, too many clients already " error.
What I am assuming is since write and read is happening simultaneously too frequently, the connection is not getting dispose properly.
Is there a way to avoid read whenever a write is happening.
EDITED
Thanks for the reply.. I know some connection pooling is happening but not sure where.. so my question was how to avoid concurrent access of postgres db..
Was not sure what part of code I can post to make the question clear
I am having using clause on dbcontext and also disposed like the below..
This is retrieval section
using (PlatinumDBContext platinumDBContext = new PlatinumDBContext())
{
try
{
var data = platinumDBContext.TrendPoints.Where(x => ids.Contains(x.TrendPointID) && x.TimeStamp >= DateTime.Now.AddHours(-timeinHours));
result = data.Select(x => new Last24hours
{
Label = x.TrendPointID.ToString(),
Value = (double)x.TrendPointValue,
time = x.TimeStamp.ToString("MM/dd/yyyy HH:mm:ss")
}).ToList();
}
catch (Exception oE)
{
}
finally {
platinumDBContext.Dispose();
}
}
This is the insertion section
using (PlatinumDBContext platinumDBContext = new PlatinumDBContext())
{
try
{
foreach (var point in trendPoints)
{
if (point != null)
{
TrendPoint item = new TrendPoint();
item.CreatedDate = DateTime.Now;
item.ObjectState = ObjectState.Added;
item.TrendPointID = point.TrendID;
item.TrendPointValue = double.IsNaN(point.Value) ? decimal.MinValue : (decimal)point.Value;
item.TimeStamp = new DateTime(point.TimeStamp);
platinumDBContext.Add(item);
}
}
platinumDBContext.SaveChanges();
}
catch (Exception ex)
{
}
finally
{
platinumDBContext.Dispose();
}
}
Regards,
Geervani
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();
}
I am trying to solve situation with rolling back our datacontexts.
We are using one TransactionScope and inside two data contexts of two different databases.
At the end we want to save changes on both databases so we call .SaveChanges but the problem is that when an error occurs on the other database the changes on the first database are still saved.
What am I doing wrong in there that the first database doesn't roll back?
Thank you,
Jakub
public void DoWork()
{
using (var scope = new TransactionScope())
{
using (var rawData = new IntranetRawDataDevEntities())
{
rawData.Configuration.AutoDetectChangesEnabled = true;
using (var dataWareHouse = new IntranetDataWareHouseDevEntities())
{
dataWareHouse.Configuration.AutoDetectChangesEnabled = true;
... some operations with the data - no savechanges() is being called.
// Save changes for all items.
if (!errors)
{
// First database save.
rawData.SaveChanges();
// Fake data to fail the second database save.
dataWareHouse.Tasks.Add(new PLKPIDashboards.DataWareHouse.Task()
{
Description = string.Empty,
Id = 0,
OperationsQueue = new OperationsQueue(),
Queue_key = 79,
TaskTypeSLAs = new Collection<TaskTypeSLA>(),
Tasktype = null
});
// Second database save.
dataWareHouse.SaveChanges();
scope.Complete();
}
else
{
scope.Dispose();
}
}
}
}
From this article http://blogs.msdn.com/b/alexj/archive/2009/01/11/savechanges-false.aspx
try to use
rawData.SaveChanges(false);
dataWareHouse.SaveChanges(false);
//if everything is ok
scope.Complete();
rawData.AcceptAllChanges();
dataWareHouse.AcceptAllChanges();
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;
}
}
See Resolving optimistic concurrency exceptions with Reload (database wins) :
using (var context = new BloggingContext())
{
var blog = context.Blogs.Find(1);
blog.Name = "The New ADO.NET Blog";
bool saveFailed;
do
{
saveFailed = false;
try
{
context.SaveChanges();
}
catch (DbUpdateConcurrencyException ex)
{
saveFailed = true;
// Update the values of the entity that failed to save from the store
ex.Entries.Single().Reload();
}
} while (saveFailed);
}
Why the method SaveChanges() is called after Reload()?
This call will never change the data in the database.
I agree it's not too clear. The intention of this piece of code is in the sentence
The entity is then typically given back to the user in some form and they must try to make their changes again and re-save.
So it would have been better if they had added a comment:
...
// User evaluates current values and may make new changes.
try
{
context.SaveChanges();
}
...