Problem Our applications are using a high number of connections and the server is very busy. How do I check whether the application is using connection pooling correctly when connecting to SQL Server? Is there an easy way to see which connections are using connection pooling and which ones are not? In this tip, I will go over how to capture this information for each logon, so you can see which connections are taking advantage of connection polling.
Solution SQL Server 2005 introduced DDL Triggers and this solution takes advantage of the DDL Logon trigger along with the EVENTDATA() function to determine if the connections are using connection pool or NOT.
Identifying this fact is very important to every DBA as the cost of opening a connection every time data is requested is expensive. The cost of each user connection is approximately (3 * network_packet_size + 94 KB) where the default network packet size is 4 KB. That means each user connection cost is approximately 130 KB. In addition, the time it takes to make the connection can also slow down processing.
Here is the script to create a table to store the data and a DDL Logon trigger to capture this data. This should be created in the master database.
--Create the dbo.ServerLogonHistory Table
CREATE TABLE dbo.ServerLogonHistory
(
EventType VARCHAR(512),
PostTime DATETIME,
SPID INT,
ServerName VARCHAR(512),
LoginName VARCHAR(512),
LoginType VARCHAR(512),
SID VARCHAR(512),
ClientHost VARCHAR(512),
IsPooled BIT
)
GO
--Create the Logon Trigger Trigger_ServerLogon
CREATE TRIGGER Trigger_ServerLogon
ON ALL SERVER WITH EXECUTE AS 'sa' FOR LOGON
AS
BEGIN
DECLARE @data XML
SET @data = EVENTDATA()
INSERT INTO dbo.ServerLogonHistory
SELECT @data.value('(/EVENT_INSTANCE/EventType)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/PostTime)[1]', 'datetime')
, @data.value('(/EVENT_INSTANCE/SPID)[1]', 'nvarchar(4)')
, @data.value('(/EVENT_INSTANCE/ServerName)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/LoginName)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/LoginType)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/SID)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/ClientHost)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/IsPooled)[1]', 'nvarchar(1)')
END
GO
In order for users to write to this table, that do not have rights to this table, I am using the EXECUTE AS clause in the trigger to run the code using the equivalent of the "sa" account. If you do not want to use the "sa" account another option is to create a new login, grant insert permissions to this table for this login and then use this login in the EXECUTE AS clause in the trigger.
Here is another way to do this by giving GRANT INSERT permissions to PUBLIC for table master.dbo.ServerLogonHistory.
--Create the dbo.ServerLogonHistory Table
CREATE TABLE dbo.ServerLogonHistory
(
EventType VARCHAR(512),
PostTime DATETIME,
SPID INT,
ServerName VARCHAR(512),
LoginName VARCHAR(512),
LoginType VARCHAR(512),
SID VARCHAR(512),
ClientHost VARCHAR(512),
IsPooled BIT
)
GO
--Grant insert rights to public for this table
GRANT INSERT ON dbo.ServerLogonHistory TO PUBLIC
--Create the Logon Trigger Trigger_ServerLogon
CREATE TRIGGER Trigger_ServerLogon
ON ALL SERVER FOR LOGON
AS
BEGIN
DECLARE @data XML
SET @data = EVENTDATA()
INSERT INTO dbo.ServerLogonHistory
SELECT @data.value('(/EVENT_INSTANCE/EventType)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/PostTime)[1]', 'datetime')
, @data.value('(/EVENT_INSTANCE/SPID)[1]', 'nvarchar(4)')
, @data.value('(/EVENT_INSTANCE/ServerName)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/LoginName)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/LoginType)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/SID)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/ClientHost)[1]', 'nvarchar(512)')
, @data.value('(/EVENT_INSTANCE/IsPooled)[1]', 'nvarchar(1)')
END
GO
Here is a sample result from the data that was collected using the above DDL trigger.
You can look at the IsPooled column to check if the connections are pooled.
1 = pooled and
0 = non-pooled connections.
Next Steps:
Here is another approach for finding connection pool information by James Rowland-Jones
In the next steps section it states there is another approach by Jamie Thompson, however the link is to James Rowland-Jones's blog :-) You should change the text to give credit to the right person.
Sankar Reddy is a Database Engineer/DBA and SQL Server MVP. He has been working with SQL Server since 2003 in a variety of roles.
