limits (max processes, max file descriptors) setting under Ubuntu 16.04 LTS doesn't take affect for mongod process

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Omry Levy

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Nov 23, 2016, 4:04:36 PM11/23/16
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Hi there,

I have installed Mongo DB 3.2 on AWS replica set, with 3 Ubuntu 16.04 LTS instances as the nodes.
I have problems setting the <Max Open Files> and <Max Processes> for the mongod process.

mongod is running under mongodb user.
other processes that run under mongodb user has 64,000 set properly , as i changed the ulimit of those , system wide, but that change didn't stick specifically with the mongod process.

I have a mongod.service script under /lib/systemd/system and it shows the following:
---------->
[Unit]
Description=High-performance, schema-free document-oriented database
After=network.target

[Service]
User=mongodb
Group=mongodb
ExecStart=/usr/bin/mongod --quiet --config /etc/mongod.conf
LimitFSIZE=infinity # file size
LimitCPU=infinity # cpu time
LimitAS=infinity # virtual memory size
LimitNOFILE=64000 # open files
LimitNPROC=64000 # processes/threads
TasksMax=infinity # total threads (user+kernel)
TasksAccounting=false
# Recommended limits for for mongod as specified in

[Install]
WantedBy=multi-user.target
<--------------


I do not have a script under /etc/init.d
i use service mongod [commands]    to control mongod

the status for mongod shows the following:
---------->
● mongod.service - High-performance, schema-free document-oriented database
   Loaded: loaded (/lib/systemd/system/mongod.service; disabled; vendor preset: enabled)
   Active: active (running) since Tue 2016-11-22 22:19:12 UTC; 7h ago
 Main PID: 13970 (mongod)
    Tasks: 72
   Memory: 82.0M
      CPU: 1min 47.637s
   CGroup: /system.slice/mongod.service
           └─13970 /usr/bin/mongod --quiet --config /etc/mongod.conf
<--------------

and the ulimits for the process shows this:
cat /proc/13970/limits
---------->
Limit                     Soft Limit           Hard Limit           Units
Max cpu time              unlimited            unlimited            seconds
Max file size             unlimited            unlimited            bytes
Max data size             unlimited            unlimited            bytes
Max stack size            8388608              unlimited            bytes
Max core file size        0                    unlimited            bytes
Max resident set          unlimited            unlimited            bytes
Max processes             31868                31868                processes
Max open files            1024                 4096                 files
Max locked memory         65536                65536                bytes
Max address space         unlimited            unlimited            bytes
Max file locks            unlimited            unlimited            locks
Max pending signals       31868                31868                signals
Max msgqueue size         819200               819200               bytes
Max nice priority         0                    0
Max realtime priority     0                    0
Max realtime timeout      unlimited            unlimited            us
<--------------

I am lost, i don't understand why mongod doesn't get the limits changes that i set for, especially when other processes like mms-automation that run under the same mongodb user get's them

Any advise ?












Kevin Adistambha

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Nov 28, 2016, 11:05:04 PM11/28/16
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Hi Omry

I have installed Mongo DB 3.2 on AWS replica set, with 3 Ubuntu 16.04 LTS instances as the nodes.

I have problems setting the and for the mongod process.

I noticed that you have submitted a JIRA ticket for this issue: https://jira.mongodb.org/browse/MMSSUPPORT-12440, and I believe the ticket was marked as solved.

Best regards,
Kevin

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