NPoco and PostgreSQL: PostgresException: 53300: sorry, too many clients already
I'm getting this error when I browse my own website allverse.co for a while. Here's the project: https://github.com/claysmith/allverse
and typical NPoco connection code in each Controller...
private IDatabase _db = new Database(new NpgsqlConnection(Startup.Configuration["PostgresConn"]), DatabaseType.PostgreSQL, NpgsqlFactory.Instance);
private IDatabase GetDB()
{
return _db;
}
public SomeFunc()
{
using(IDatabase db = GetDB())
{
try
{
article.id = (long)db.Insert(article);
}
catch(Exception ex)
{
string m = ex.Message;
string im = ex.InnerException.ToString();
}
}
}
Do I need to increase my postgresql connections or am I not closing connections somewhere? Thanks.
Related
We wrote our own simple execution strategy to retry saving any data using our DbContext when it runs into a table lock timeout.
public class RetryTransactionExecutionStrategy : DbExecutionStrategy
{
public RetryTransactionExecutionStrategy() : base()
{
}
protected override bool ShouldRetryOn(Exception exception)
{
while (exception != null)
{
if (exception is MySqlException ex
&& ex.Number == 1205) // Deadlock error code
{
return true;
}
exception = exception.InnerException;
}
return false;
}
}
We register it by using the DbConfig class, in the same folder as the context class.
public class DbConfig : DbConfiguration
{
public DbConfig()
{
SetExecutionStrategy(MySqlProviderInvariantName.ProviderName, () => new RetryTransactionExecutionStrategy());
}
}
Now most regular usage of the context will use the retry execution strategy. However, transactions are a more special case. Microsoft mentions usage of them in their documentation, and tells the user to manually call the execution strategy, like this:
var executionStrategy = new RetryTransactionExecutionStrategy();
executionStrategy.Execute(() =>
{
using (PigDbAccountEntities pigDbAccountEntities = new PigDbAccountEntities())
{
using (var dbtransaction = pigDbAccountEntities.Database.BeginTransaction())
{
try
{
//work on some data
pigDbAccountEntities.SaveChanges();
//work on some more data
pigDbAccountEntities.SaveChanges();
//work on even more data
pigDbAccountEntities.SaveChanges();
dbtransaction.Commit();
isSaved = true;
}
catch (Exception ex)
{
dbtransaction.Rollback();
Logger.Instance.Log(LogLevel.ERROR, LogSource.DB, "error in AccountEntityManager.SaveApplicationUser", ex);
}
}
}
});
And yet we still get this error message:
The configured execution strategy 'RetryTransactionExecutionStrategy' does not support user initiated transactions. See http://go.microsoft.com/fwlink/?LinkId=309381 for additional information.
Any idea on what to do/check?
we are trying to upgrade to CSLA 6.
now, we are getting a message:
"ConnectionManager is obsolete, use dependency injection ... use ApplicationContext.LocalContext"
for this code:
using (var ctx = ConnectionManager<OracleConnection>.GetManager("dbEndpoint", true))
We've tried this code snippet but all connections is NULL.
Could you please help us to correctly get Connection?
var services = new ServiceCollection();
services.AddCsla();
var provider = services.BuildServiceProvider();
DataPortalFactory = provider.GetRequiredService<IDataPortalFactory>();
var appContext = provider.GetRequiredService<Csla.ApplicationContext>();
var conn1 = appContext.LocalContext.GetValueOrNull("dbEndpoint");
var conn2 = appContext.LocalContext.GetValueOrNull("__db:default-dbEndpoint");
var conn3 = appContext.LocalContext["dbEndpoint"];
var conn4 = appContext.LocalContext["__db:default-dbEndpoint"];
another experiment:
....
var CONNECTION_ORACLE = new OracleConnection(ConfigurationManager.ConnectionStrings["dbEndpoint"].ConnectionString);
services.AddScoped<IDbConnection>(o => CONNECTION_ORACLE);
....
var provider = services.BuildServiceProvider();
...
var connectionResolved = provider.GetRequiredService<IDbConnection>();
appContext.LocalContext.Add("dbEndpoint", connectionResolved);
then connection is not null;
and inside of Factory is successfully resolved by DI:
public DocFactory(ApplicationContext appContext, IDbConnection connection) : base(
appContext)
{
_connection = connection;
}
then
[Fetch]
public Doc_Fetch(DocCriteria criteria)
{
bool cancel = false;
OnFetching(criteria, ref cancel);
if (cancel) return null;
Doc item = null;
OracleConnection connection = _connection as OracleConnection;
connection is Closed (but NOT null!!). it's possible to open it but if close it, somebody else consuming it will face with a problem or child objects also will face problem with closed connection.
so, making ConnectionManager as Obsolete may be not so obvious way to go. But ConnectionManager was very useful for counting open connection, supporting transactions etc
Could you please provide a workaround for it.
more attempts:
var connectionString =
ConfigurationManager.ConnectionStrings["dbEndpoint"].ConnectionString;
..
appContext.ClientContext.Add("DBConnectionString", connectionString );
...
Factory
using (var connection = new OracleConnection(ApplicationContext.ClientContext["DBConnectionString"].ToString()))
{
connection.Open();
Your DAL should require that a database connection be injected.
public class MyDal : IDisposable
{
public MyDal(OracleConnection connection)
{
Connection = connection;
}
private OracleConnection Connection { get; set; }
public MyData GetData()
{
// use Connection to get the data
return data;
}
public void Dispose()
{
Connection.Dispose();
}
}
Then in the app server startup code, register your DAL type(s) and also register your connection type.
services.AddScoped(typeof(OracleConnection), () =>
{
// initialize the connection here
return connection;
});
services.AddScoped<MyDal>();
Then, in your data portal operation method (such as create, fetch, etc.), inject your DAL:
[Fetch]
private void Fetch([Inject] MyDal dal)
{
var data = dal.GetData();
}
I am trying to connect my Android Application to Postgres but seems not to work.
The Exception Message is: Exception while Connecting
This is my Code Behind,
private void Login_Clicked(object sender, EventArgs e)
{
DBInterface<DBLogicInput, DBLogicResult> dbLoginLogic = new DBLoginLogic();
DBLogicInput userInput = new DBLogicInput();
DBLogicResult DBResult = new DBLogicResult();
LoginModel useCredentials = new LoginModel()
{
userName = txtUsername.Text,
passWord = txtPassword.Text
};
userInput[typeof(LoginModel).FullName] = useCredentials;
try
{
DBResult = dbLoginLogic.DoProcess(userInput);
bool userExisting = DBResult.ResultCode != DBLogicResult.RESULT_CODE_ERR_DATA_NOT_EXIST;
if (userExisting)
{
Application.Current.MainPage = new NavigationPage(new IndexPage());
}
else
{
_ = DisplayAlert("Login Error", "User does not exist", "Ok");
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
This is the Class I created to connect the DB.
public abstract class DBLogic : DBInterface<DBLogicInput, DBLogicResult>
{
public string connectionString = "Server=localhost;Port=5432;User Id=postgres;Password=postgres;Database=proyektoNijuan";
public DBLogicResult DoProcess(DBLogicInput inOut)
{
//throw new NotImplementedException();
DBLogicResult result = default(DBLogicResult);
NpgsqlConnection connection = null;
NpgsqlTransaction transaction = null;
try {
connection = new NpgsqlConnection(connectionString);
if (connection.State != System.Data.ConnectionState.Open)
{
connection.Open();
}
transaction = connection.BeginTransaction();
result = Process(connection, inOut);
transaction.Commit();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
transaction.Rollback();
} finally {
if (connection != null)
{
connection.Close();
}
}
return result;
}
protected abstract DBLogicResult Process(NpgsqlConnection conn, DBLogicInput InOuT);
}
The error exists after the debugger hits the code connection.Open();.
Should I add a web services to connect the postgres to my android app built in xamarin forms?
I am only a beginner in Xamarin Forms. I am just trying to create a self application. And need a little help for me to learn a new platform in programming.
Thank you and Regards,
How to fix it?
Well, I think I am doing it wrong.
Maybe the Right way to Connect the PostgreSQL is to have a WEB API.
Calling that web API to the Xamarin forms.
I really don't know if it is correct, but I will give it a try.
I will update the correct answer after I finish the development of that WEB API so that other beginners will found this answer helpful.
I am developing a stand alone application, using sql server compact 3.5 sp2 which runs in process. No Database writes involved. Its purely a reporting application. Read many articles about reusing open db connections in case of sql compact(connection pooling) due to its different behavior from sql server.
Quoting the comments from a quiz opened by Erik Ejlskov Jensen Link, where its discussed an open early close late strategy for sql server compact databases. Based on this, with my limited experience I have implemented a not so complex Connection handling+Data access layer. Basically I am unsure if i am writing it in a recommended way. Please could any one point me in the right direction with rooms for improvement in this connection handling approach i have written?
The DbConnection class
public class FkDbConnection
{
private static SqlCeConnection conn;
private static DataTable table;
private static SqlCeCommand cmd;
~FkDbConnection() { conn = null; }
//This will be called when the main winform loads and connection will be open as long as the main form is open
public static string ConnectToDatabase()
{
try {
conn = new SqlCeConnection(ConfigurationManager.ConnectionStrings["Connstr"].ConnectionString);
if (conn.State == ConnectionState.Closed || conn.State == ConnectionState.Broken)
{
conn.Open();
}
return "Connected";
}
catch(SqlCeException e) { return e.Message; }
}
public static void Disconnect()
{
if (conn.State == ConnectionState.Open || conn.State == ConnectionState.Connecting || conn.State == ConnectionState.Fetching)
{
conn.Close();
conn.Dispose();
//conn = null; //does conn have to be set to null?
}
//else the connection might be already closed due to failure in opening it
else if (conn.State == ConnectionState.Closed) {
conn.Dispose();
//conn = null; //does conn have to be set to null?
}
}
/// <summary>
/// Generic Select DataAccess
/// </summary>
/// <param name="sql"> the sql query which needs to be executed by command object </param>
public static DataTable ExecuteSelectCommand(SqlCeCommand comm)
{
if (conn != null && conn.State == ConnectionState.Open)
{
#region block using datareader
using (table = new DataTable())
{
//using statement needed for reader? Its closed below
using (SqlCeDataReader reader = comm.ExecuteReader())
{
table.Load(reader);
reader.Close(); //is it needed?
}
}
#endregion
# region block using dataadpater
//I read DataReader is faster?
//using (SqlCeDataAdapter sda = new SqlCeDataAdapter(cmd))
//{
// using (table = new DataTable())
// {
// sda.Fill(table);
// }
//}
#endregion
//}
}
return table;
}
/// <summary>
/// Get Data
/// </summary>
/// <param name="selectedMPs"> string csv, generated from a list of selected posts(checkboxes) from the UI, which forms the field names used in SELECT </param>
public static DataTable GetDataPostsCars(string selectedMPs)
{
DataTable dt;
//i know this it not secure sql, but will be a separate question to pass column names to select as parameters
string sql = string.Format(
"SELECT " + selectedMPs + " "+
"FROM GdRateFixedPosts");
using (cmd = new SqlCeCommand(sql,conn))
{
cmd.CommandType = CommandType.Text;
//cmd.Parameters.Add("#fromDateTime",DbType.DateTime);
//cmd.Parameters.Add("#toDateTime",DbType.DateTime);
dt = ExecuteSelectCommand(cmd);
}
return dt;
}
}
The Main UI (Form) in which connection opened, for connection to be open through out. 2 other reporting forms are opened from here. Closing main form closes all, at which point connection is closed and disposed.
private void FrmMain_Load(object sender, EventArgs e)
{
string str = FkDbConnection.ConnectToDatabase();
statStDbConnection.Items[0].Text = str;
}
private void FrmMain_FormClosing(object sender, FormClosingEventArgs e)
{
FkDbConnection.Disconnect();
}
Comments, improvements on this connection class much appreciated. See my questions also inline code
Thank you.
Updated classes as per Erik's suggestion. with a correction on ExecuteSelectCommand() and an additional class which will instantiate command objs in "using" and pass data to the UI. I intent to add separate GetDataForFormX() methods since the dynamic sql for each form may differ. Hope this is ok?
Correction to Erik's code:
public static DataTable ExecuteSelectCommand(SqlCeCommand comm)
{
var table = new DataTable();
if (conn != null && conn.State == ConnectionState.Open)
{
comm.Connection = conn;
using (SqlCeDataReader reader = comm.ExecuteReader())
{
table.Load(reader);
}
}
return table;
}
New FkDataAccess class for passing Data to UI
public class FkDataAccess
{
public static DataTable GetDataPostsCars(string selectedMPs)
{
var table = new DataTable();
string sql = string.Format(
"SELECT " + selectedMPs + " " +
"FROM GdRateFixedPosts");
if (FkDbConnection.conn != null && FkDbConnection.conn.State == ConnectionState.Open)
{
using (SqlCeCommand cmd = new SqlCeCommand(sql, FkDbConnection.conn))
{
cmd.CommandType = CommandType.Text;
//cmd.Parameters.Add("#fromDateTime",DbType.DateTime);
table = FkDbConnection.ExecuteSelectCommand(cmd);
}
}
return table;
}
//public static DataTable GetDataXY(string selectedvals)
// and so on
}
Too much code in your data access class, makes it unreadable and hard to maintain
The SqlCeonnection object will be disposed when you close it (and when the app closes)
You cannot dispose the DataTable if you want to use it elsewhere, and it is an completely managed object anyway.
It is a good pattern to limit your classes to a single responsibility
public class FkDbConnection
{
private static SqlCeConnection conn;
~FkDbConnection() { conn = null; }
//This will be called when the main winform loads and connection will be open as long as the main form is open
public static void ConnectToDatabase()
{
// Handle failure to open in the caller
conn = new SqlCeConnection(ConfigurationManager.ConnectionStrings["Connstr"].ConnectionString);
conn.Open();
}
public static void Disconnect()
{
if (conn != null)
{
conn.Close();
}
}
public static DataTable ExecuteSelectCommand(SqlCeCommand comm)
{
var table = new DataTable();
if (conn != null && conn.State == ConnectionState.Open)
{
comm.Connection = conn;
using (SqlCeDataReader reader = comm.ExecuteReader())
{
table.Load(reader);
}
}
return table;
}
private void FrmMain_Load(object sender, EventArgs e)
{
try
{
FkDbConnection.ConnectToDatabase();
statStDbConnection.Items[0].Text = "Connected";
}
catch (Exception ex)
{
//Inform use that we canot proceed, what she can do to remedy, and exit
}
}
private void FrmMain_FormClosing(object sender, FormClosingEventArgs e)
{
FkDbConnection.Disconnect();
}
This is the error which arises when I tried to debug an application under Visual C# 2010
I write that code to retrieve some rows from a database table, I already attached the two well known databases Pubs and Northwind to the db explorer, but the error remains
class Author
{
SqlConnection _pubConnection;
string _connString;
public Author()
{
_connString = "Data Source=./INSTANCE2;Initial Catalog=pubs;Integrated Security=True";
_pubConnection = new SqlConnection();
_pubConnection.ConnectionString = _connString;
}
public int CountAuthors()
{
try
{
SqlCommand pubCommand = new SqlCommand();
pubCommand.Connection = _pubConnection;
pubCommand.CommandText = "Select Count(au_id) from authors";
_pubConnection.Open();
return (int)pubCommand.ExecuteScalar();
}
catch (SqlException ex)
{
throw ex;
}
finally
{
if (_pubConnection != null)
{
_pubConnection.Close();
}
}
}
}
static void Main(string[] args)
{
try
{
Author author = new Author();
Console.WriteLine(author.CountAuthors());
Console.ReadLine();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
Console.ReadLine();
}
}
the Connection string isn't ok , i correct it and it works fine