Using NodeJS 100% cpu - epoll_wait

Question

Im trying to keep track of why the nodejs application is suddenly using a 100% processor. The application has about 50 simultaneous connections and runs on an ec2 micro instance.

Below is the result: strace -c node server.js

 ^C% time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 87.32 0.924373 8 111657 epoll_wait 6.85 0.072558 3 22762 pread 2.55 0.026965 0 146179 write 0.92 0.009733 0 108434 1 futex 0.44 0.004661 0 82010 7 read 0.44 0.004608 0 223317 clock_gettime 0.31 0.003244 0 172467 gettimeofday 0.31 0.003241 35 93 brk 0.20 0.002075 0 75233 3 epoll_ctl 0.19 0.002052 0 23850 11925 accept4 0.19 0.001997 0 12302 close 0.19 0.001973 7 295 mmap 0.06 0.000617 4 143 munmap 

And here is the conclusion: node-tick-processor

  [Top down (heavy) profile]: Note: callees occupying less than 0.1% are not shown. inclusive self name ticks total ticks total 669160 97.4% 669160 97.4% /lib/x86_64-linux-gnu/libc-2.15.so 4834 0.7% 28 0.0% LazyCompile: *Readable.push _stream_readable.js:116 4750 0.7% 10 0.0% LazyCompile: *emitReadable _stream_readable.js:392 4737 0.7% 19 0.0% LazyCompile: *emitReadable_ _stream_readable.js:407 1751 0.3% 7 0.0% LazyCompile: ~EventEmitter.emit events.js:53 1081 0.2% 2 0.0% LazyCompile: ~<anonymous> _stream_readable.js:741 1045 0.2% 1 0.0% LazyCompile: ~EventEmitter.emit events.js:53 960 0.1% 1 0.0% LazyCompile: *<anonymous> /home/ubuntu/node/node_modules/redis/index.js:101 948 0.1% 11 0.0% LazyCompile: RedisClient.on_data /home/ubuntu/node/node_modules/redis/index.js:541 

This is my first node app debugging. Are there any conclusions that can be drawn from the above debug output? Where could there be a mistake?

Edit

My node version: v0.10.25

Edit 2

After upgrading node to: v0.10.33

Here is the conclusion

 ^C% time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 91.81 1.894522 8 225505 45 epoll_wait 3.58 0.073830 1 51193 pread 1.59 0.032874 0 235054 2 write 0.98 0.020144 0 1101789 clock_gettime 0.71 0.014658 0 192494 1 futex 0.57 0.011764 0 166704 21 read 

Answer 1

Looks like a Node JS v0.10.25 error with an event loop, look here .

Note: this github pull request:

If the same file description is open in two different processes, then closing the file descriptor is not enough to undo it from the epoll instance (as described in epoll (7)), which leads to false events that cause the event loop to rotate repeatedly. Therefore, always explicitly cancel it.

So, as a solution, you can try updating your OS or updating Node JS.