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POHow to debug Node + Socket.io CPU Issues
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  1. POHow to debug Node + Socket.io CPU Issues
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    copied!<p>We are running a Node Socket.io server with Express 3. The server is monitored using <a href="https://github.com/nodejitsu/forever" rel="noreferrer">Forever</a>. The service is running well, but the CPU grows throughout the day, until it reaches 90%+ and then suddenly drops back down to ~20%, as shown in the graphs below. I believe that the drop is caused by Forever restarting the app.</p> <p><img src="https://i.stack.imgur.com/jZhAt.png" alt="CPU Behaviour"></p> <p>What I would like to know is;</p> <ul> <li>What are the typical factors that could cause a Node.js app to behave like this? </li> <li>What tools / methods are available to debug memory leaks / cpu hogging in node apps?</li> </ul> <p>I think it could be something to do with Socket.io not cleaning up resources once users have disconnected, although the docs say that Socket.io will manage this automatically.</p> <p>Any help would be greatly appreciated, this issue is making managing our server very difficult. I have posted this question on Serverfault a week ago, but did not receive a response, so I think it may be better here.</p> <p><strong>Update:</strong> After more research, it appears that the CPU does not directly correlate with the number of connections. Our critical mass seems to be around ~1500 concurrent connections split up like so:</p> <ul> <li>xhr-polling: 767</li> <li>websocket: 692</li> <li>jsonppolling: 80</li> </ul> <p>Sometimes we could be at 100% CPU with only 500 connections, other times its 1500 connections. I'm aware that the rate of messages sent has a big affect, however the rate is fairly consistent.</p>
 

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