we are using mongo 3.0.3, when we see mongo connections goes beyond 1700 then the databases becomes unresponsive until the number of connections comes down to 1000 or below. the whole process taking more than 30 min. how can we avoid this clocking ?

what parameters need to checked at the time of high connections. 

when we checked the db.currentOp() - the result is empty but if we check db.currentOp(true) it shows more than 1500 idle connections.