For some days I have searched for a working solution to an error
Error: EMFILE, too many open files
It seems that many people have the same problem. The usual answer involves increasing the number of file descriptors. So, I've tried this:
sysctl -w kern.maxfiles=20480
,
The default value is 10240. This is a little strange in my eyes, because the number of files I'm handling in the directory is under 10240. Even stranger, I still receive the same error after I've increased the number of file descriptors.
Second question:
After a number of searches I found a work around for the "too many open files" problem:
var requestBatches = {};
function batchingReadFile(filename, callback) {
// First check to see if there is already a batch
if (requestBatches.hasOwnProperty(filename)) {
requestBatches[filename].push(callback);
return;
}
// Otherwise start a new one and make a real request
var batch = requestBatches[filename] = [callback];
FS.readFile(filename, onRealRead);
// Flush out the batch on complete
function onRealRead() {
delete requestBatches[filename];
for (var i = 0, l = batch.length; i < l; i++) {
batch[i].apply(null, arguments);
}
}
}
function printFile(file){
console.log(file);
}
dir = "/Users/xaver/Downloads/xaver/xxx/xxx/"
var files = fs.readdirSync(dir);
for (i in files){
filename = dir + files[i];
console.log(filename);
batchingReadFile(filename, printFile);
Unfortunately I still recieve the same error. What is wrong with this code?
For when graceful-fs doesn't work... or you just want to understand where the leak is coming from. Follow this process.
(e.g. graceful-fs isn't gonna fix your wagon if your issue is with sockets.)
From My Blog Article: http://www.blakerobertson.com/devlog/2014/1/11/how-to-determine-whats-causing-error-connect-emfile-nodejs.html
This command will output the number of open handles for nodejs processes:
lsof -i -n -P | grep nodejs
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
...
nodejs 12211 root 1012u IPv4 151317015 0t0 TCP 10.101.42.209:40371->54.236.3.170:80 (ESTABLISHED)
nodejs 12211 root 1013u IPv4 151279902 0t0 TCP 10.101.42.209:43656->54.236.3.172:80 (ESTABLISHED)
nodejs 12211 root 1014u IPv4 151317016 0t0 TCP 10.101.42.209:34450->54.236.3.168:80 (ESTABLISHED)
nodejs 12211 root 1015u IPv4 151289728 0t0 TCP 10.101.42.209:52691->54.236.3.173:80 (ESTABLISHED)
nodejs 12211 root 1016u IPv4 151305607 0t0 TCP 10.101.42.209:47707->54.236.3.172:80 (ESTABLISHED)
nodejs 12211 root 1017u IPv4 151289730 0t0 TCP 10.101.42.209:45423->54.236.3.171:80 (ESTABLISHED)
nodejs 12211 root 1018u IPv4 151289731 0t0 TCP 10.101.42.209:36090->54.236.3.170:80 (ESTABLISHED)
nodejs 12211 root 1019u IPv4 151314874 0t0 TCP 10.101.42.209:49176->54.236.3.172:80 (ESTABLISHED)
nodejs 12211 root 1020u IPv4 151289768 0t0 TCP 10.101.42.209:45427->54.236.3.171:80 (ESTABLISHED)
nodejs 12211 root 1021u IPv4 151289769 0t0 TCP 10.101.42.209:36094->54.236.3.170:80 (ESTABLISHED)
nodejs 12211 root 1022u IPv4 151279903 0t0 TCP 10.101.42.209:43836->54.236.3.171:80 (ESTABLISHED)
nodejs 12211 root 1023u IPv4 151281403 0t0 TCP 10.101.42.209:43930->54.236.3.172:80 (ESTABLISHED)
....
Notice the: 1023u (last line) - that's the 1024th file handle which is the default maximum.
Now, Look at the last column. That indicates which resource is open. You'll probably see a number of lines all with the same resource name. Hopefully, that now tells you where to look in your code for the leak.
If you don't know multiple node processes, first lookup which process has pid 12211. That'll tell you the process.
In my case above, I noticed that there were a bunch of very similar IP Addresses. They were all 54.236.3.###
By doing ip address lookups, was able to determine in my case it was pubnub related.
Use this syntax to determine how many open handles a process has open...
I used this command to test the number of files that were opened after doing various events in my app.
lsof -i -n -P | grep "8465" | wc -l
# lsof -i -n -P | grep "nodejs.*8465" | wc -l
28
# lsof -i -n -P | grep "nodejs.*8465" | wc -l
31
# lsof -i -n -P | grep "nodejs.*8465" | wc -l
34
ulimit -a
The line you want will look like this:
open files (-n) 1024
In case you are expecting to open many connections (websockets is a good example), you can permanently increase the limit:
file: /etc/pam.d/common-session (add to the end)
session required pam_limits.so
file: /etc/security/limits.conf (add to the end, or edit if already exists)
root soft nofile 40000
root hard nofile 100000
restart your nodejs and logout/login from ssh.
this may not work for older NodeJS you'll need to restart server
use instead of if your node runs with different uid.