Make drop database close and release resources

Drop database did not close any open shard files or close
any topic reader/heartbeats.  In the tests, we create and drop new
databases during each test run so these were open files and connection
slowed things down and consumed a lot of RAM as the tests progressed.

client/influxdb.go

@@ -45,7 +45,7 @@ func NewClient(c Config) (*Client, error) {
 		url:        c.URL,
 		username:   c.Username,
 		password:   c.Password,
-		httpClient: &http.Client{},
+		httpClient: http.DefaultClient,
 		userAgent:  c.UserAgent,
 	}
 	if client.userAgent == "" {

messaging/client.go

@@ -34,11 +34,11 @@ const (
 // Client represents a client for the broker's HTTP API.
 type Client struct {
 	mu      sync.Mutex
-	path    string    // config file path
-	conns   []*Conn   // all connections opened by client
-	url     url.URL   // current known leader URL
-	urls    []url.URL // list of available broker URLs
-	dataURL url.URL   // URL of the client's data node
+	path    string           // config file path
+	conns   map[uint64]*Conn // all connections opened by client
+	url     url.URL          // current known leader URL
+	urls    []url.URL        // list of available broker URLs
+	dataURL url.URL          // URL of the client's data node
 
 	opened bool
 
@@ -61,6 +61,7 @@ func NewClient(dataURL url.URL) *Client {
 		ReconnectTimeout: DefaultReconnectTimeout,
 		PingInterval:     DefaultPingInterval,
 		dataURL:          dataURL,
+		conns:            map[uint64]*Conn{},
 	}
 	return c
 }
@@ -353,12 +354,31 @@ func (c *Client) Conn(topicID uint64) *Conn {
 	conn := NewConn(topicID, &c.dataURL)
 	conn.SetURL(c.url)
 
+	if _, ok := c.conns[topicID]; ok {
+		panic(fmt.Sprintf("connection for topic %d already exists", topicID))
+	}
 	// Add to list of client connections.
-	c.conns = append(c.conns, conn)
+	c.conns[topicID] = conn
 
 	return conn
 }
 
+// CloseConn closes the connection to the broker for a given topic
+func (c *Client) CloseConn(topicID uint64) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if conn, ok := c.conns[topicID]; ok && conn != nil {
+		if err := conn.Close(); err != nil {
+			return err
+		}
+
+		delete(c.conns, topicID)
+	}
+
+	return nil
+}
+
 // pinger periodically pings the broker to check that it is alive.
 func (c *Client) pinger(closing chan struct{}) {
 	defer c.wg.Done()

server.go

@@ -1015,8 +1015,38 @@ func (s *Server) applyDropDatabase(m *messaging.Message) (err error) {
 	// Remove from metastore.
 	err = s.meta.mustUpdate(m.Index, func(tx *metatx) error { return tx.dropDatabase(c.Name) })
 
+	db := s.databases[c.Name]
+	for _, rp := range db.policies {
+		for _, sg := range rp.shardGroups {
+			for _, sh := range sg.Shards {
+
+				// if we have this shard locally, close and remove it
+				if sh.store != nil {
+					// close topic readers/heartbeaters/etc. connections
+					err := s.client.CloseConn(sh.ID)
+					if err != nil {
+						panic(err)
+					}
+
+					err = sh.close()
+					if err != nil {
+						panic(err)
+					}
+
+					err = os.Remove(s.shardPath(sh.ID))
+					if err != nil {
+						panic(err)
+					}
+				}
+
+				delete(s.shards, sh.ID)
+			}
+		}
+	}
+
 	// Delete the database entry.
 	delete(s.databases, c.Name)
+
 	return
 }
 
@@ -3518,6 +3548,7 @@ type MessagingClient interface {
 
 	// Conn returns an open, streaming connection to a topic.
 	Conn(topicID uint64) MessagingConn
+	CloseConn(topicID uint64) error
 }
 
 type messagingClient struct {

test/messaging.go

@@ -90,6 +90,24 @@ func (c *MessagingClient) Conn(topicID uint64) influxdb.MessagingConn {
 	return c.ConnFunc(topicID)
 }
 
+func (c *MessagingClient) CloseConn(topicID uint64) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	conns := []*MessagingConn{}
+	for _, conn := range c.conns {
+		if conn.topicID == topicID {
+			if err := conn.Close(); err != nil {
+				return err
+			}
+			continue
+		}
+		conns = append(conns, conn)
+	}
+	c.conns = conns
+	return nil
+}
+
 // DefaultConnFunc returns a connection for a specific topic.
 func (c *MessagingClient) DefaultConnFunc(topicID uint64) influxdb.MessagingConn {
 	c.mu.Lock()