OPMS multiple shm/overlay filesystem entries created - is the number configurable?

Products

• CA App Synthetic Monitor
• DX Application Performance Management

Issue/Introduction

We have installed an OPMS on new server and have observed that there are multiple shm/overlay filesystem entries present in the df output.

# df
Filesystem     1K-blocks     Used Available Use% Mounted on
...
overlay         62903276 13439232  49464044  22% /var/lib/docker/overlay2/4c3c53                                                   8099fd9c3dd4859bcc21b48a45882c06c43567cb84d2bd97ea7fd47e3e/merged
...
overlay         62903276 13439232  49464044  22% /var/lib/docker/overlay2/9d77fa                                                   4c6075fb14526267c913766747d62f08bfc22e77684a2f171e80eb7a05/merged
shm                65536        0     65536   0% /var/lib/docker/containers/2cef                                                   9a094655696cc2d43bffed578eb8cb32ffa61489aab278509822acfe43ca/mounts/shm
shm                65536        0     65536   0% /var/lib/docker/containers/cc8f                                                   b5a23936ae3aea0252cce92584bf306ebb38ef8f55bacaefb69b5defe538/mounts/shm
...

Why are there so many and is the number configurable?

Environment

• Release: 10.4
• Component: App Synthetic Monitor OPMS

Resolution

• The shm/overlay 'filesystems' are present due to the docker images that the OPMS starts.
• The number of instances of the docker images started (jmeter2, jmeter4, rbtm) is determined by the OPMS installer based on the number of CPU cores available and is designed to give an optimal performance.
• We therefore do not recommend changing the configured values.