I just solve it!
After I checked “/opt/librenms/includes/polling/cisco-remote-access-monitor.inc.php” this file, the cras_sessions.rrd will be create after LibreNMS detected “Mail Proxy”, “LAN to LAN tunnel”, “IPsec tunnel”, “Load Balancing sessions”. “SVC session” and “WebVPN session” this 6 features on Cisco ASA.
If there have one of above feature missing on Cisco ASA, then LibreNMS would not create “cras_sessions.rrd” and you won’t see the graph on the portal.
Because I didn’t enable Email proxy on ASAv, and it won’t be enabled in our environment, so I changed configuration on “/opt/librenms/includes/html/graphs/device/cras_sessions.inc.php” and “/opt/librenms/includes/polling/cisco-remote-access-monitor.inc.php” to ignored mail proxy feature, then I can see the graph display on the portal.
But this solution seems cause existing rrd file crash, and the value will display with “NaN”, so I still need to figure it out.