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What version of MongoDB are you using (mongod --version)?

3.4

What version of Go are you using (go version)?

1.11

What did you do?

my program uses the mgo to connect to a mongo shard cluster. When the concurrent requests increase rapidly, some of my mongo query would return err like "insert err:write results unavailable from ${ip} :: caused by :: Location11002: socket exception [CONNECT_ERROR]".

I think the socket occurs some network connection error, so I use the following code to get a new session(I.e. socket)

session.Close()
globalSession.Copy()

The problem seems to be solved.

recently, I have dig into some of the source code and have some questions for the following code:

// Release decrements a socket reference. The socket will be
// recycled once its released as many times as it's been acquired.
func (socket *mongoSocket) Release() {
	socket.Lock()
	if socket.references == 0 {
		panic("socket.Release() with references == 0")
	}
	socket.references--
	stats.socketRefs(-1)
	if socket.references == 0 {
		stats.socketsInUse(-1)
		server := socket.server
		closeAfterIdle := socket.closeAfterIdle
		socket.Unlock()
		socket.LogoutAll()
		if closeAfterIdle {
			socket.Close()
		} else if server != nil {
			// If the socket is dead server is nil.
			server.RecycleSocket(socket)
		}
	} else {
		socket.Unlock()
	}
} 

Here is my question: if a socket that has some network connection error(like I said above) is put back to the unusedSockets slice by calling the session.Close(), which calls socket.Release(), will I encounter the error again when I use the session acquire the socket from unusedSockets? Have not seen any code to ensure the socket available(or I just missed)

Thks!