Three metrics show values of zero when monitoring an Apache instance with the SNMP module:
Bytes received for GET requests per minute
Bytes received for POST requests per minute
Total number of bytes received per minute
This is because of how SNMP interprets information from the request body. First, SNMP provides various length values for the request body and a GET request does not have a body, so GET responses are not calculated and, therefore, have a value of zero. Second, Apache does not calculate a request body size if there is request chunking.