How to determine if the Entity Framework is waiting on a connection from the connection pool?

问题

I’m seeing some intermittent slowdown \ sql timeout errors that I’m having trouble determining the cause. I’ve pieced together some clues but I need some help figuring out possible next steps.

The Problem

We have a table that has 10+ million records that we run an async count from our web application. The table is written to often. Occasionally the count takes 2 minutes, sometime it timeouts, and sometimes it returns under a second all from the same generated sql.

I have a theory that the all the connections in the connection pool are busy so it's waiting... but I don't know of a way to prove it.

Our Setup

SQL 2012, Entity Framework 5.0, and the MVC Web API.

Clues

During the slow response times I can run the same sql via sql management studio and it returns under a second.
During the slow response times all other functionality of the site performs fine, slowness is confined to this area.
Problem only occurs on Production database. I've tried to reproduce it on development without any luck.

What I've tried so far

We had a problem where the count was locking the table and timing
out. Because the table was locked for such a long time it caused
havoc with our application. We changed the scope to “read
un-committed” and that seems to have fixed locking problem but not
the timeout.
Profiled the queries generated by entity framework

Details

Looking at SQL Profiler here are the queries run.

-- network protocol: LPC
set quoted_identifier on
set arithabort off
set numeric_roundabort off
set ansi_warnings on
set ansi_padding on
set ansi_nulls on
set concat_null_yields_null on
set cursor_close_on_commit off
set implicit_transactions off
set language us_english
set dateformat mdy
set datefirst 7
set transaction isolation level read uncommitted



 exec sp_executesql N'SELECT 
    [GroupBy1].[A1] AS [C1]
    FROM ( SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[CampaignSendResults] AS [Extent1]
        WHERE ([Extent1].[CampaignId] = @p__linq__0) AND (0 =  CAST( [Extent1].[ResultType] AS int))
    )  AS [GroupBy1]',N'@p__linq__0 uniqueidentifier',@p__linq__0='0BACD499-A665-4721-902A-37EAB49A8A8C'


exec sp_executesql N'SELECT 
[GroupBy1].[A1] AS [C1]
FROM ( SELECT 
    COUNT(1) AS [A1]
    FROM [dbo].[CampaignSendResults] AS [Extent1]
    WHERE ([Extent1].[CampaignId] = @p__linq__0) AND (0 =  CAST( [Extent1].[ResultType] AS int)) AND ( CAST( [Extent1].[SendDate] AS datetime2) >= @p__linq__1)
)  AS [GroupBy1]',N'@p__linq__0 uniqueidentifier,@p__linq__1 datetime2(7)',@p__linq__0='0BACD499-A665-4721-902A-37EAB49A8A8C',@p__linq__1='2013-07-23 00:35:12.6930000'

回答1:

The problem could be

set arithabort off

it should be

set arithabort on

来源：https://stackoverflow.com/questions/17816472/how-to-determine-if-the-entity-framework-is-waiting-on-a-connection-from-the-con

标签

sql-server

entity-framework-5