[SNMP4J] Statistics about number of retries and snmp request times

[Michał Steiner]

Hi
Here is my quick feedback just from looking at code:

It would be very helpful to see Javadoc with explanation what event below
mean exactly

  // SNMP4J-STATISTICS-MIB
snmp4jStatsRequestTimeouts
snmp4jStatsRequestRetries
snmp4jStatsRequestWaitTime
snmp4jStatsResponseTimeouts
snmp4jStatsResponseIgnoredRetries
snmp4jStatsResponseProcessTime

Also in what time unit there are given - I noticed
 constant HUNDREDTHS_TO_NANOSECOND (tenth of milliseconds BTW why not ms  ?)

Javadoc for org.snmp4j.Snmp#getCounterSupport   is
missing snmp4jStatsRequestRetries but it has
duplicated snmp4jStatsRequestTimeouts.


Also I think it would be very useful from monitoring perspective to publish
size of  collections: pendingRequests and asyncRequests. It would be enough
to create two getters calling pendingRequests .size() and
asyncRequests.size()

Regards
Michal