Implement clean up routine to backend as some backends may require

e.g closing database connections on unmount to avoud connection
stacking.

logical/framework/backend.go

@@ -51,6 +51,10 @@ type Backend struct {
 	Rollback       RollbackFunc
 	RollbackMinAge time.Duration
 
+	// Clean is called on unload to clean up e.g any existing connections
+	// to the backend, if required.
+	Clean          CleanupFunc
+
 	// AuthRenew is the callback to call when a RenewRequest for an
 	// authentication comes in. By default, renewal won't be allowed.
 	// See the built-in AuthRenew helpers in lease.go for common callbacks.
@@ -68,6 +72,9 @@ type OperationFunc func(*logical.Request, *FieldData) (*logical.Response, error)
 // RollbackFunc is the callback for rollbacks.
 type RollbackFunc func(*logical.Request, string, interface{}) error
 
+// CleanupFunc is the callback for backend unload.
+type CleanupFunc func()
+
 // logical.Backend impl.
 func (b *Backend) HandleRequest(req *logical.Request) (*logical.Response, error) {
 	b.once.Do(b.init)
@@ -147,6 +154,11 @@ func (b *Backend) Setup(config *logical.BackendConfig) (logical.Backend, error)
 	return b, nil
 }
 
+func (b *Backend) Cleanup() {
+	if b.Clean != nil {
+		b.Clean()
+	}
+}
 // Logger can be used to get the logger. If no logger has been set,
 // the logs will be discarded.
 func (b *Backend) Logger() *log.Logger {

logical/logical.go

@@ -26,6 +26,8 @@ type Backend interface {
 	// System provides an interface to access certain system configuration
 	// information, such as globally configured default and max lease TTLs.
 	System() SystemView
+
+	Cleanup()
 }
 
 // BackendConfig is provided to the factory to initialize the backend

vault/mount.go

@@ -461,8 +461,17 @@ func (c *Core) setupMounts() error {
 }
 
 // unloadMounts is used before we seal the vault to reset the mounts to
-// their unloaded state. This is reversed by load and setup mounts.
+// their unloaded state, calling Cleanup if defined. This is reversed by load and setup mounts.
 func (c *Core) unloadMounts() error {
+	if c.mounts != nil {
+		for _, e := range c.mounts.Entries {
+			prefix := e.Path
+			b, ok := c.router.root.Get(prefix)
+			if ok {
+				b.(*mountEntry).backend.Cleanup()
+			}
+		}
+	}
 	c.mounts = nil
 	c.router = NewRouter()
 	c.systemBarrierView = nil

vault/router.go

@@ -75,6 +75,12 @@ func (r *Router) Mount(backend logical.Backend, prefix string, mountEntry *Mount
 func (r *Router) Unmount(prefix string) error {
 	r.l.Lock()
 	defer r.l.Unlock()
+
+	// Call backend's Cleanup routine
+	me, ok := r.root.Get(prefix)
+	if ok {
+		me.(*mountEntry).backend.Cleanup()
+	}
 	r.root.Delete(prefix)
 	return nil
 }

vault/router_test.go

@@ -49,6 +49,10 @@ func (n *NoopBackend) System() logical.SystemView {
 	}
 }
 
+func (n *NoopBackend) Cleanup() {
+	// noop
+}
+
 func TestRouter_Mount(t *testing.T) {
 	r := NewRouter()
 	_, barrier, _ := mockBarrier(t)

vault/testing.go

@@ -272,3 +272,7 @@ func (n *rawHTTP) System() logical.SystemView {
 		MaxLeaseTTLVal:     time.Hour * 24 * 30,
 	}
 }
+
+func (n *rawHTTP) Cleanup() {
+	// noop
+}