Concurrent Processes Limitation
What Is a Process?
Processes are the execution of a command within the server that completes a specific task. An example would be accessing your email account and responding to a letter. This action is achieved through a series of processes that normally complete within moments of each other. The process limitation depends on the account hosting type.
Shared and Reseller Hosting
Shared and Reseller plans are limited to 25 simultaneous processes per cPanel. Most sites will work perfectly with a 25 concurrent processes limit. Processes open and close so quickly that they hardly ever overlap.
If a user has between 15-19 IMAP processes running, our system automatically kills any process running over 5 minutes. If more than 20 IMAP processes are running, our system will automatically kill any process running for longer than 2 minutes.
SSH access is limited to two simultaneous connections on Shared and Reseller plans.
Dedicated and VPS Hosting
Dedicated Servers and VPS plans allow for an adjustable number of simultaneous processes with no enforced limit.
Check Processes in cPanel
To check processes in cPanel:
- Log into cPanel.
- Scroll Down to the Statistics section.
- Locate the Processes bar, which will display the number of processes running at one time.
The bar should refresh after 60 seconds; however, if you wish to see if the processes update sooner, refresh the page.
Mail Client Exceeding Processes Limit
If you are exceeding the processes limit, this could be caused by your mail client (Thunderbird, Mac Mail, Outlook, etc.) checking for emails too many times in an hour.
Once the limit is reached, the server stores the check as a process to be handled after the 30 checks reset; however, more requests from your mail client keep coming. Therefore, more and more processes are stored until the 25 process limit is reached, bringing your site down with a 500 error message.
How to Determine if Your Mail Client is the Problem
Try the steps below to determine if your mail client is causing your website to exceed the processes limit.
- Close the mail client to clear all the processes. You will then be able to see the site load back up right away.
- After seeing the site pull back up, open the client, and locate the setting for how often your mail client checks the server for emails. The setting should not be less than 10 minutes apart.
If you are still hitting the process limit, you either have too much traffic for a Shared server, or you need to optimize your database for faster queries.
What If My VPS or Dedicated Server is Limiting Me to 25 Processes?
This number can be increased at your discretion by making changes in the following file: /usr/local/apache/conf/includes/pre_main_global.conf
To make the appropriate changes, use the command line:
RLimitNPROC 25 30
- Change the first number to the new limit (in the command above, it is the 25)
- Add 5 to get the second number (in the command above, 30)
- Restart Apache (location: /etc/init.d/httpd, command: restart).
After Apache is restarted, you should be able to see the new process limit functioning accordingly.