How does connection pooling works? i want to know that if i set max. pool size = 20 so are only 20 users able to connect to the web app. at a same time and make a transaction ? What happens to the large websites like Amazon where thousands of users log in at same time throughout the world i.e what pool size do they keep? i am not getting the core concept. I know that a connection pool keeps open connections and users reuse the open connections but i want my first question to be answered.
There is no such document where you can find the maximum size of the pool.Default value of max pool size is 100
Check out MSDN
There can be maximum 32767 connections to the database at a time. That is, at a single point of time only 32767 users can make transactions to database via web app. Not even one more than that. A pool size is not mentioned anywhere only default is there(100). But SQL Server will only accept 32767 connections from user. Proof: Select ##MAX_CONNECTIONS . If misunderstood please correct me.
The user connections option specifies the maximum number of simultaneous user connections that are allowed on an instance of SQL Server. The actual number of user connections allowed also depends on the version of SQL Server that you are using, and also the limits of your application or applications and hardware. SQL Server allows a maximum of 32,767 user connections. Because user connections is a dynamic (self-configuring) option, SQL Server adjusts the maximum number of user connections automatically as needed, up to the maximum value allowable.
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We have a big application that uses 40 microservices (Spring boot) that each have about 5 database connections to a mariadb server. That causes too many connection errors on our mariadb server. Default is 151 however I was thinking of just setting the max connections to 1000 to be on the safe side. I cant find anywhere on the Internet if this is possible or even wise. Our MariaDB is running standalone on a VPS with 8GB memory. It is not running in a docker container or something like that. It is run directly on the VPS.
What is the maximum connections advisable taking into consideration that we might scale up with our microservices?
You can scale up your max_connections just fine. Put a line like
max_connections=250
in your MariaDB my.cnf file. But don't just set it to a very high number; each potential connection consumes RAM, and with only 8GiB you need to be a bit careful about that.
If you give this command you'll get a bunch of data about your connections.
SHOW STATUS LIKE '%connect%';
The important ones to watch:
Connection_errors_max_connections The number of connection attempts that failed because you ran out of connection slots.
Connections The total number of connections ever handled
Max_used_connections The largest number of simultaneous connections used.
Max_used_connections_time The date and time when the server had its largest number of connections.
The numbers shown are cumulative since the last server boot or the most recent FLUSH STATUS; statement.
Keep an eye on these. If you run short you can always add more. If you have to add many more connections as you scale up, you probably will need to provision your VPS with more RAM. The last two are cool because you can figure out whether you're getting hammered at a particular time of day.
And, in your various microservices be very careful to use connection pools of reasonable maximum size. Don't let your microservices grab more than ten connections unless you run into throughput trouble. You didn't say what client tech you use (nodejs? dotnet? php? Java?) so it's hard to give you specific advice how to do that.
In my IIS Server, I have many application pools (like 6 to 7) and there are many ASP.NET applications running on each of them (ex. 25 applications per pool). They all are connected with Oracle database by using ADO.NET.
All applications are just working fine, but sometimes we get error like
Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
I know the possibilities for this like we are not closing our database connections properly. So here is my headache... I don't want to go each and every project to see where we forget to close connections it is very time taking task for us.
So is there any way to identify from which application connections are remaining opened? Can we see from IIS itself? Can we make some kind of utility to track from which project connection are remaining opened?
I'm not sure that it's a probleme of the connection to database. I think that you application are not disposing the context then the garbage collector can't clear memory. you can try to reduce the time for recylcling your application pools then check if you memory usage is decreasing or not.
I am trying to implement the Connection Pool in my project. I need to count the number of connection that i need at a particular time so that i can set the maximum limit of connection for connection pool. Can any one guide me how can i check, how many connections are using at a particular time.
I am creating a .net application, with a Sql Server db engine. I would like my site to be accessed by thousands of users per second. What does the number of connections rely on?
How many connection can IIS hold, and Sql Server?
First, there is a difference between connections and connection pools. Is it good to look into that, as it makes a huge difference in performance. If you need a reference, I can dig one up, but google/bing is your friend here. The key takeaway is: keep the number of connections pool to a minimum.
With that said, the number of connection depends on two things.
Are you using Windows Auth? If so, every distinct user will cause a distinct connection/connection pool
If you are using SQL Auth, then each different connection string will cause a new pool to be created (even a single space difference will cause a new pool).
In regards to the scaling question, both IIS and SQL Server can handle an very high number of connections. If you are running into connection limits, you should probably take a look at the application design.
Erick
The number of connections is really dependent on the physical makeup and optimization of your server and how far you can push it. You can down-throttle the number of concurrent connections in the IIS configuration as well as in SQL if you want to put a limit on how many connections should be allowed.
That is no problem for Windows and or SQL Server:
Windows is configured by default to handle 1000 to 2000 concurrent tcpip connections.
For SQL Server, it will also depend on the licenses and or hardware which you did not specify. What kind of hardware is SQL going on ?
You can set a limit yourself, or find out what limit has already been put in place in your IIS server settings.
http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/b2b550de-f655-4fb6-9bed-dfc9583b6700.mspx?mfr=true
Does the same connection string used on two different physical servers hosting different web applications that talk to the same database draw connections from the same connection pool? Or are pooled connections confined to at the application level?
I ask because I inherited a 7 year old .NET 1.1 web application which is riddled with in-line SQL, unclosed and undisposed sql connection and datareader objects. Recently, I was tasked to write a small web app that is hosted on another server and talks to the same database and therefore used the same database connection string. I created a LINQ object to read and write the one table required by the app. Now the original .NET 1.1 app is throwing exceptions like
"Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached."
Maybe these are unreleated, but wanted to get your opinions to make sure I cover all my bases.
Thanks!
There is no way connections can be pooled between two separate machines. Your SQL Server will have a connection limit for total connections however.
This error is most likely occurring because the application is not returning connections to the connection pool. This can happen because the connection is not being disposed of correctly. This can happen due to poor code (does it use a using block, or a try catch finally?) or if using a SQLDataReader can cause the connection to stay open after the code to execute the SQL has exited.
Connection Pools are kept in your App Pool, so it shouldn't be possible for a separate machine to steal out of a separate boxes App Pool. Have a look here for some info on the connection pool. I'd also recommend slapping the performance counters on see bottom of this article to see what's going on in there a bit more.
Also might want to check the max number of connections on SQL Server. In management Studio
Right click on the Server name --> Properties --> Connections
look for "Maximum number of concurrent connections (0 = unlimited)"