• sensor_srv.py
• sensor_pub.py
• listener.py

The publisher sensors_pub.py can publish all memory fields, 1st example or a single memory field, 2nd example. The listener will see a string value for the field or a serialised dictionary of all fields.

$ rostopic echo /all_mem

data: "{"available": 13586079744, "used": 2278055936, "free": 12225290240, "inactive"
: 810291200, "active": 2909175808, "total": 16387588096, "slab": 255102976,
\ "buffers": 167620608, "cached": 1716621312, "percent": 17.1, "shared"
: 186216448}"

$ rostopic echo /free_mem

data: "12177854464"

The sensor_srv.py script provides a ROS service that responds with the host's memory details. It also will reconnect to ROS master should master go down and then come back-up again. The specific memory field can be requested or all fields. The response is a serialised dictionary

$ rosservice call /get_memory free

response: "{"epoch": 1663869477, "free": 11780108288}"

$ rosservice call /get_memory available

response: "{"available": 12972105728, "epoch": 1663869484}"

$ rosservice call /get_memory all

response: "{"available": 12956168192, "used": 2882674688, "free": 11757998080, "inactive": 835198976, "active": 3317071872, "total": 16387588096, "slab": 234094592, "buffers": 143945728, "cached": 1602969600, "percent": 20.9, "epoch": 1663869494, "shared": 228298752}"

• Running the script and log output

The publisher / service scripts can recover from roscore going down and coming back up.

$ /usr/bin/python /home/andy/catkin_ws/src/andy_msc/scripts/sensor_srv.py

[INFO] [1663869420.587280]: /sensor_srv initiated
[INFO] [1663869477.930538]: /sensor_srv: get_memory_details called with service: free
[INFO] [1663869484.764102]: /sensor_srv: get_memory_details called with service: available
[INFO] [1663869494.098081]: /sensor_srv: get_memory_details called with service: All
22.09.2022-18:59:13: /sensor_srv - ROS master went offine
[WARN] [1663869553.588671]: unable to communicate with ROS Master, registrations are now out of sync
22.09.2022-18:59:17: /sensor_srv - ROS master is online

• Memory.srv