Here is a bit of V2.0 C# code using PerformanceCounters that shows each
appdomain has its own connection pool for SqlClient. Pooling happens in
native code for Odbc & OleDb, so their pooling is per process.
using System;
using System.Data.SqlClient;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;
class CrossDomain : System.MarshalByRefObject {
[DllImport("kernel32.dll")]
private static extern int GetCurrentProcessId();
private static string GetAssemblyName() {
Assembly assembly = Assembly.GetEntryAssembly();
if (null != assembly) {
AssemblyName name = assembly.GetName();
return name.Name;
}
return null;
}
private static string GetInstanceName() {
string instanceName = GetAssemblyName();
if (String.IsNullOrEmpty(instanceName)) {
AppDomain appDomain = AppDomain.CurrentDomain;
if (null != appDomain) {
instanceName = appDomain.FriendlyName;
}
}
int pid = GetCurrentProcessId();
return String.Format("{0}[{1}]", instanceName, pid);
}
public string Start(string constr) {
using(SqlConnection c = new SqlConnection(constr)) {
c.Open();
}
return GetInstanceName();
}
}
class Program {
private static void NumberOfActiveConnectionPools(string name) {
PerformanceCounter instance = new PerformanceCounter();
instance.CategoryName = ".NET Data Provider for SqlServer";
instance.CounterName = "NumberOfActiveConnectionPools";
instance.InstanceName = name;
instance.ReadOnly = true;
Console.WriteLine("{0}: NumberOfActiveConnectionPools={1}",
instance.InstanceName, instance.RawValue);
}
public static void Main(string[] args) {
try {
CrossDomain c0 = new CrossDomain();
AppDomain ad =AppDomain.CreateDomain("Test");
CrossDomain c1 =
(CrossDomain)ad.CreateInstanceFromAndUnwrap(Assembly.GetExecutingAssembly().Location,
typeof(CrossDomain).FullName);
string name1 = c0.Start("Data Source=.;integrated
security=sspi");
string name2 = c1.Start("Data Source=.;integrated
security=sspi");
string name3 = c1.Start("server=.;trusted_connection=sspi");
NumberOfActiveConnectionPools(name1);
NumberOfActiveConnectionPools(name2);
if (name2 != name3) {
NumberOfActiveConnectionPools(name3);
}
}
catch (Exception e) {
Console.WriteLine(e);
}
}
}
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David Browne said:
A Process is divided into one or more App Domain. Connection Pools are
scoped to the App Domain, just like any global/static variable.
David
: David mentioned that it is per database, acutally