Callpoint callback's are exists but showing: db error: application communication failure

CDB and CDB API
1

I registered a callpoint for one of the snmp stats table, but the get_elem() callback function status is coming as below: (confd --check-callbacks o/p)

/<MIB-name>/Table/StatsEntry[index='index'][diskName='diskName']/ops - exists()... ***: db error: application timeout
/<MIB-name>/Table/StatsEntry[index='index'][diskName='diskName']/ops - get_elem()... ***: db error: application communication failure

And whenever callbacks are in this states, snmpwalk is failing, in between, with the timeout error as mentioned below:
Timeout: No Response from

This failure I am seeing intermittently, thus not able to figure out the root cause for this.
And one weird behavior I saw, once after restarting the services the callbacks start working as expected and thus snmpwalk also.

Please share your insights on this topic.

2

almost always means there is some problem with external app that implements a callbacks…
This could be - app not running/callback not registered, crash, timeout, incorrect data provider “protocol usage” (mismatched value types/return code/other), etc.

Make sure you have developer log level enabled with trace in ConfD, and see if devel.log contains more info/problems reported for callbacks being run…