Database Connection Counts (Advanced Topic)
PaperCut technical support are sometimes asked “How many database connections will PaperCut need?”
It’s a fairly innocuous question, but giving an exact answer is not easy as there are many variables that contribute to how many database connections PaperCut will use.
For example, the following events can cause one or more database connections to happen:
- Startup and Restarts of the PaperCut Application Server
- Startup and Restarts of Secondary Servers
- Performing a print job
- Making copies/scans at a copier
- Releasing print jobs at a copier
- the PaperCut User Client starting or updating
- Logging into the PaperCut User Web Interface or Admin Interface
- Intranet’s or other external systems using PaperCut’s various API’s
- Payment Gateways
- Using Release Stations
- Running reports
- Overnight maintenance (such as backups and syncing of users)
- Quota allocations
- and more…
As you can see PaperCut has many areas where it will momentarily use a database to either read, update or store new information.
Obviously we have gone to lengths to make sure we’re as efficient as caffinely possible. We make use of Connection Pooling and Connection Reuse algorithms. For example, one connection might be used to update a users balance because they’ve just printed a document, then a few milliseconds later we need to check the email address of another user, we’ll re-use that connection rather than close and reopen one. Once a connection has become idle for a while (configurable) we’ll close the connection.
This means that the total number of database connections can not be directly correlated to the number of print jobs, user sessions or copiers, etc as not all of these processes happen at the same time.
Under normal operating conditions the number of database connections will remain consistently low. The number will increase to meet demand and reduce down afterwards. This can lead to spikes in the number of connections during busy moments, for example a remote office’s internet connection has started working again or a large batch of print jobs is released.
Please note: Unexpected behaviour can occur if a database has been configured to restrict the number of connections that PaperCut can make to an external DBMS. For sites dealing with high print volumes and many users, this number may need to be as high as 400 simultaneous connections.
Keywords: database connection limits, too many connections, how many connections