Connections closing due to "terminating connection due to administrator command"

Hello everybody.

In the past week, it has happened to us twice already that we got an exception from our Java application, due to PostgreSQL "terminating connection due to administrator command”.

The problem is that I’m the administrator, and I issued no such command.

On the first opportunity that it happened, the PostgreSQL server actually seemed to have spontaneously shut itself down and restarted:

2015-07-21 15:37:59 IDT LOG: received fast shutdown request
2015-07-21 15:37:59 IDT LOG: aborting any active transactions
2015-07-21 15:37:59 IDT FATAL: terminating connection due to administrator command
…
2015-07-21 15:38:01 IDT LOG: shutting down
2015-07-21 15:38:02 IDT LOG: database system is shut down
2015-07-21 15:40:16 IDT LOG: database system was shut down at 2015-07-21 15:38:02 IDT

On today’s occasion, the server seems to be continuing as usual, and there is nothing whatsoever in the log.

So my questions are:

* Given that I did not terminate any backend connection interactively, why did I get a "terminating connection due to administrator command” message? Is there any situation where this message is issued without the administrator being involved?
* What could have caused the shutdown on the 21st of July? Again, I did not issue a shutdown request for that server, and the machine didn’t restart.

The server is running PostgreSQL 9.1.16.

Thank you,
Herouth