Thursday, September 15, 2016

MongoDB Start Up Issues & Warnings

While taking backup of MongoDB using Ops Manager cloud control, we came across various warnings at different stages. 
following are the warnings that one may come across during start of the Head DB.

WARNING: soft rlimits too low. rlimits set to 4096 processes, 64000 files.

##Pls create following file if not already present.

 cat /etc/security/limits.d/90-nproc.conf
* soft nproc 64000
* hard nproc 64000

Make sure to reboot the system after the change.

As we are using Data Domain to store snapshots and SAN for Head DB, another error we faced was following.

unable to create or lock mongod.lock file

Here the issue was with the options we used to mount the file we changed the options to include following.

nolock, noatime, nointr

There were also some more warnings regarding NUMACTL not installed. 
one way is to install the numactl on backup daemon server with the help of SA. 
we can disable it using Ops Manager UI as follows.

Non-Uniform Memory Access (NUMA) Settings

Key - mongodb.disable.numa
Value Type: boolean

To disable NUMA for the head databases:

1.Click the Admin link, then the General tab, then the Ops Manager Config page, and then the Custom section.
2.Add mongodb.disable.numa as a Key and set its Value to true.
3.Click Save.