Hi,

We are using Mongo replica-set (3 Mongo servers - 1 Primary, 1 secundary, 1 arbiter).
Mongo version 3.2.17.

We had a problem on 10.10.2017 between 11:44:10 - 11:51:00 hours.

We know that we started dropIndex on one collection and commad executed ok:
2017-10-10T09:44:06.738+0000 I COMMAND [conn92280] CMD: dropIndexes igraci.listici

After that, all operation on+ all databases were very slow+ (about 5~6 minutes) , number of connections started to get very high and logs are full of
2017-10-10T09:50:58.824+0000 I NETWORK [conn93396] SocketException handling request, closing client connection: 9001 socket exception [SEND_ERROR] server x.z.y.a

All our application were slowed in query execution, insert too.

Based on documentation https://docs.mongodb.com/manual/reference/command/dropIndexes/index.html only the affected database shoud be lock, but not all others and we think this happend.

In attachment are logs.

We can't explain our self what happend so asking for your help?
Thanks