Skip to content

sp_BlitzFirst: add Top 5 server/login/app breakdown to High Number of Connections #3921

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
BrentOzar merged 3 commits into from
Apr 15, 2026
Merged

sp_BlitzFirst: add Top 5 server/login/app breakdown to High Number of Connections #3921

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
dbf2ecf
sp_BlitzFirst: add Top 5 server/login/app breakdown to High Number of…
BrentOzar Apr 15, 2026
cd914b7
Revert version/date bump on line 50
BrentOzar Apr 15, 2026
dc10aef
sp_BlitzFirst CheckID 49: fix XPath and missing line break in Details…
BrentOzar Apr 15, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
168 changes: 159 additions & 9 deletions sp_BlitzFirst.sql
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2664,15 +2664,165 @@ If one of them is a lead blocker, consider killing that query.'' AS HowToStopit,

IF @max_worker_threads > 0
BEGIN
INSERT INTO #BlitzFirstResults (CheckID, Priority, FindingsGroup, Finding, URL, Details)
SELECT 49 AS CheckID,
210 AS Priority,
'Potential Upcoming Problems' AS FindingGroup,
'High Number of Connections' AS Finding,
'https://www.brentozar.com/archive/2014/05/connections-slow-sql-server-threadpool/' AS URL,
'There are ' + CAST(SUM(1) AS VARCHAR(20)) + ' open connections, which would lead to ' + @LineFeed + 'worker thread exhaustion and THREADPOOL waits' + @LineFeed + 'if they all ran queries at the same time.' AS Details
FROM sys.dm_exec_connections c
HAVING SUM(1) > @max_worker_threads;
/* Count connections first so we only build the Top 5 breakdowns when the
alert actually fires. See issue #3903 for the feature request. */
DECLARE @TotalConnections INT;
SET @TotalConnections = (SELECT COUNT(*) FROM sys.dm_exec_connections);

Comment thread
BrentOzar marked this conversation as resolved.
IF @TotalConnections > @max_worker_threads
BEGIN
/* Load connection + session attributes into a table variable once so we can
aggregate it three different ways (by host, login, and app) without
re-reading the DMVs. sys.dm_exec_sessions.last_request_end_time defaults
to 1900-01-01 for sessions that have never run a request - treat that
sentinel as NULL so it renders as "unknown" rather than "45000 days ago". */
DECLARE @ConnSessions TABLE
(
HostName NVARCHAR(128) NOT NULL,
LoginName NVARCHAR(128) NOT NULL,
AppName NVARCHAR(128) NOT NULL,
LastFinish DATETIME NULL
);

INSERT INTO @ConnSessions (HostName, LoginName, AppName, LastFinish)
SELECT
COALESCE(NULLIF(s.host_name, N''), N'(unknown host)'),
COALESCE(NULLIF(s.login_name, N''), N'(unknown login)'),
COALESCE(NULLIF(s.program_name, N''), N'(unknown app)'),
NULLIF(s.last_request_end_time, CONVERT(DATETIME, '1900-01-01'))
FROM sys.dm_exec_connections c
LEFT JOIN sys.dm_exec_sessions s ON s.session_id = c.session_id;

DECLARE @TopServers NVARCHAR(MAX),
@TopLogins NVARCHAR(MAX),
@TopApps NVARCHAR(MAX);

SELECT @TopServers = STUFF((
SELECT @LineFeed
+ g.ConnectionGroup + ' - ' + CAST(g.ConnectionCount AS VARCHAR(20)) + ' connections'
+ ', most recent query finished '
+ CASE
WHEN g.MostRecentSec IS NULL THEN 'unknown'
WHEN g.MostRecentSec < 60 THEN CAST(g.MostRecentSec AS VARCHAR(10)) + ' seconds ago'
WHEN g.MostRecentSec < 3600 THEN CAST(g.MostRecentSec / 60 AS VARCHAR(10)) + ' minutes ago'
WHEN g.MostRecentSec < 86400 THEN CAST(g.MostRecentSec / 3600 AS VARCHAR(10)) + ' hours '
+ CAST((g.MostRecentSec % 3600) / 60 AS VARCHAR(10)) + ' minutes ago'
ELSE CAST(g.MostRecentSec / 86400 AS VARCHAR(10)) + ' days '
+ CAST((g.MostRecentSec % 86400) / 3600 AS VARCHAR(10)) + ' hours ago'
END
+ ', oldest query finished '
+ CASE
WHEN g.OldestSec IS NULL THEN 'unknown'
WHEN g.OldestSec < 60 THEN CAST(g.OldestSec AS VARCHAR(10)) + ' seconds ago'
WHEN g.OldestSec < 3600 THEN CAST(g.OldestSec / 60 AS VARCHAR(10)) + ' minutes ago'
WHEN g.OldestSec < 86400 THEN CAST(g.OldestSec / 3600 AS VARCHAR(10)) + ' hours '
+ CAST((g.OldestSec % 3600) / 60 AS VARCHAR(10)) + ' minutes ago'
ELSE CAST(g.OldestSec / 86400 AS VARCHAR(10)) + ' days '
+ CAST((g.OldestSec % 86400) / 3600 AS VARCHAR(10)) + ' hours ago'
END
FROM (
SELECT TOP (5)
ConnectionGroup = HostName,
ConnectionCount = COUNT(*),
MostRecentSec = DATEDIFF(SECOND, MAX(LastFinish), GETDATE()),
OldestSec = DATEDIFF(SECOND, MIN(LastFinish), GETDATE())
FROM @ConnSessions
GROUP BY HostName
ORDER BY COUNT(*) DESC, HostName
) g
ORDER BY g.ConnectionCount DESC, g.ConnectionGroup
FOR XML PATH(''), TYPE
).value(N'.[1]', N'NVARCHAR(MAX)'), 1, LEN(@LineFeed), N'');

SELECT @TopLogins = STUFF((
SELECT @LineFeed
+ g.ConnectionGroup + ' - ' + CAST(g.ConnectionCount AS VARCHAR(20)) + ' connections'
+ ', most recent query finished '
+ CASE
WHEN g.MostRecentSec IS NULL THEN 'unknown'
WHEN g.MostRecentSec < 60 THEN CAST(g.MostRecentSec AS VARCHAR(10)) + ' seconds ago'
WHEN g.MostRecentSec < 3600 THEN CAST(g.MostRecentSec / 60 AS VARCHAR(10)) + ' minutes ago'
WHEN g.MostRecentSec < 86400 THEN CAST(g.MostRecentSec / 3600 AS VARCHAR(10)) + ' hours '
+ CAST((g.MostRecentSec % 3600) / 60 AS VARCHAR(10)) + ' minutes ago'
ELSE CAST(g.MostRecentSec / 86400 AS VARCHAR(10)) + ' days '
+ CAST((g.MostRecentSec % 86400) / 3600 AS VARCHAR(10)) + ' hours ago'
END
+ ', oldest query finished '
+ CASE
WHEN g.OldestSec IS NULL THEN 'unknown'
WHEN g.OldestSec < 60 THEN CAST(g.OldestSec AS VARCHAR(10)) + ' seconds ago'
WHEN g.OldestSec < 3600 THEN CAST(g.OldestSec / 60 AS VARCHAR(10)) + ' minutes ago'
WHEN g.OldestSec < 86400 THEN CAST(g.OldestSec / 3600 AS VARCHAR(10)) + ' hours '
+ CAST((g.OldestSec % 3600) / 60 AS VARCHAR(10)) + ' minutes ago'
ELSE CAST(g.OldestSec / 86400 AS VARCHAR(10)) + ' days '
+ CAST((g.OldestSec % 86400) / 3600 AS VARCHAR(10)) + ' hours ago'
END
FROM (
SELECT TOP (5)
ConnectionGroup = LoginName,
ConnectionCount = COUNT(*),
MostRecentSec = DATEDIFF(SECOND, MAX(LastFinish), GETDATE()),
OldestSec = DATEDIFF(SECOND, MIN(LastFinish), GETDATE())
FROM @ConnSessions
GROUP BY LoginName
ORDER BY COUNT(*) DESC, LoginName
) g
ORDER BY g.ConnectionCount DESC, g.ConnectionGroup
FOR XML PATH(''), TYPE
).value(N'.[1]', N'NVARCHAR(MAX)'), 1, LEN(@LineFeed), N'');

SELECT @TopApps = STUFF((
SELECT @LineFeed
+ g.ConnectionGroup + ' - ' + CAST(g.ConnectionCount AS VARCHAR(20)) + ' connections'
+ ', most recent query finished '
+ CASE
WHEN g.MostRecentSec IS NULL THEN 'unknown'
WHEN g.MostRecentSec < 60 THEN CAST(g.MostRecentSec AS VARCHAR(10)) + ' seconds ago'
WHEN g.MostRecentSec < 3600 THEN CAST(g.MostRecentSec / 60 AS VARCHAR(10)) + ' minutes ago'
WHEN g.MostRecentSec < 86400 THEN CAST(g.MostRecentSec / 3600 AS VARCHAR(10)) + ' hours '
+ CAST((g.MostRecentSec % 3600) / 60 AS VARCHAR(10)) + ' minutes ago'
ELSE CAST(g.MostRecentSec / 86400 AS VARCHAR(10)) + ' days '
+ CAST((g.MostRecentSec % 86400) / 3600 AS VARCHAR(10)) + ' hours ago'
END
+ ', oldest query finished '
+ CASE
WHEN g.OldestSec IS NULL THEN 'unknown'
WHEN g.OldestSec < 60 THEN CAST(g.OldestSec AS VARCHAR(10)) + ' seconds ago'
WHEN g.OldestSec < 3600 THEN CAST(g.OldestSec / 60 AS VARCHAR(10)) + ' minutes ago'
WHEN g.OldestSec < 86400 THEN CAST(g.OldestSec / 3600 AS VARCHAR(10)) + ' hours '
+ CAST((g.OldestSec % 3600) / 60 AS VARCHAR(10)) + ' minutes ago'
ELSE CAST(g.OldestSec / 86400 AS VARCHAR(10)) + ' days '
+ CAST((g.OldestSec % 86400) / 3600 AS VARCHAR(10)) + ' hours ago'
END
FROM (
SELECT TOP (5)
ConnectionGroup = AppName,
ConnectionCount = COUNT(*),
MostRecentSec = DATEDIFF(SECOND, MAX(LastFinish), GETDATE()),
OldestSec = DATEDIFF(SECOND, MIN(LastFinish), GETDATE())
FROM @ConnSessions
GROUP BY AppName
ORDER BY COUNT(*) DESC, AppName
) g
ORDER BY g.ConnectionCount DESC, g.ConnectionGroup
FOR XML PATH(''), TYPE
).value(N'.[1]', N'NVARCHAR(MAX)'), 1, LEN(@LineFeed), N'');

INSERT INTO #BlitzFirstResults (CheckID, Priority, FindingsGroup, Finding, URL, Details)
VALUES (
49,
210,
'Potential Upcoming Problems',
'High Number of Connections',
'https://www.brentozar.com/archive/2014/05/connections-slow-sql-server-threadpool/',
'There are ' + CAST(@TotalConnections AS VARCHAR(20)) + ' open connections, which would lead to ' + @LineFeed
+ 'worker thread exhaustion and THREADPOOL waits' + @LineFeed
+ 'if they all ran queries at the same time.'
+ @LineFeed + @LineFeed + 'Top 5 Servers:' + @LineFeed + ISNULL(@TopServers, '(none)')
+ @LineFeed + @LineFeed + 'Top 5 Logins:' + @LineFeed + ISNULL(@TopLogins, '(none)')
+ @LineFeed + @LineFeed + 'Top 5 Apps:' + @LineFeed + ISNULL(@TopApps, '(none)')
);
END
END
END

Expand Down