Setting up ulimit for ArrayServer

From Array Suite Wiki

When ArrayServer is running a large number of analyses, such as parallel jobs for 200 alignments. You may get Thread creation failed error. The error is caused by the limit in a linux machine. Make sure the ulimit for "max user processes" and "open files" are set to the max value: 65536. You can check the values by typing: ulimit -a.

$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 515184
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65536
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 65536
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

Modify ulimit in two config files following ulimit setup wiki.

Most of time, the error is caused by the process (-u) and open files (-n) limits.

In Linux, ArrayServer is run under Mono platform. Each mono job may occupy up to 20 processes (to open files, loading dll, etc.). Therefore, our recommendation is to change the process limit and file limit from 1024 to 65536 to make sure your server can handle hundreds of jobs.

Note: When ArrayServer is running on a cluster submission machine and with cluster enabled, most of jobs are running on the cluster nodes. ArrayServer will create processes in submission machine to monitor the project progress. For each qsub job, it will have a process to monitor the cluster job progress using qstat/qacct. These jobs are not computational intensive but they will use the quotas. Therefore, the limit on the cluster submission machine will also cause the error.

Change ulimit

Login as root to change system settings.

There are two places where changes need to be recorded:


sysctl.conf is for setting a system wide ceiling:

# max open files (systemic limit)
fs.file-max = 65536

limits.conf is for setting a user space floor and ceiling:


Ensure both a hard limit and a soft limit are set, otherwise the setting will not become active.

For example: to set the number of files and processes any user of the system may have open at a given time to 65536

*        soft    nofile           65536
*        hard    nofile           65536
*        soft    nproc           65536
*        hard    nproc           65536

Note, user * does not include user root. You should additional lines for root.

root        soft    nofile           65536
root        hard    nofile           65536
root        soft    nproc           65536
root        hard    nproc           65536

You have to log out and login again to make these limit effective. Login as ArrayServer admin linux account, double check these limits using ulimit -a before restarting ArrayServer to use the system settings. For more information, please google "Increasing ulimit number of files and processes limit on Linux".

double check the file /etc/security/limits.d/*-nproc.conf as this is likely overriding your settings


One of our super-users also recommended a command to raise the limit temporarily

sudo sh -c "ulimit -n 65536 && exec su $LOGNAME"

Error Message Example

Error occured.
Thread creation failed.@@@
StackTrace=  at System.Threading.Thread.Start () [0x00000] in <filename unknown>:0 
 at System.Threading.Thread.Start (System.Object parameter) [0x00000] in <filename unknown>:0 
 at Omicsoft.JobRunner.Run (ILogger logger, Omicsoft.Job job, Int32 cpuNumber) [0x00000] in <filename unknown>:0