Unable to perform graceful shutdown with new node

[bgrieder]

Hi,

I am using geth as a library (version: 1.8.8) and instantiating a new node on a (private) Clique network.

The node sets-up the Genesis block in the DB just fine.
When trying to shut down the node however, the node locks when trying to close the DB

The problem is that it is indefinitely waiting for quitChan in ethdb/database.go#Close():

if db.quitChan != nil {
	errc := make(chan error)
	db.quitChan <- errc    // <= This line
	if err := <-errc; err != nil {
		db.log.Error("Metrics collection failed", "err", err)
	}
}

The reason is that nothing is ever sent to quitChan because the function func (db *LDBDatabase) meter(refresh time.Duration) returns before ever using the channel.

Since the DB is new, the following test makes it return too early because leveldb.iostats does not exist

	ioStats, err := db.db.GetProperty("leveldb.iostats")
	if err != nil {
		db.log.Error("Failed to read database iostats", "err", err)
		return
	}

I believe, inside the if test, the statement db.quitChan = nil should be inserted to skip over the test in Close().

I guess the same reasoning applies to the test on leveldb.stats

(alternatively, why should missing levelddb.iostats cause the meter function to return, rather than the inner loop to continue?)