state/api: implement machine watching

state/api/error.go

Index: state/api/error.go 
=== modified file 'state/api/error.go' 
--- state/api/error.go	2013-02-18 18:34:59 +0000 
+++ state/api/error.go	2013-02-20 17:47:27 +0000 
@@ -2,7 +2,6 @@ 
 
 import ( 
	"errors" 
-	"launchpad.net/juju-core/log" 
	"launchpad.net/juju-core/rpc" 
	"launchpad.net/juju-core/state" 
 ) 
@@ -25,10 +24,12 @@ 
 var _ rpc.ErrorCoder = (*Error)(nil) 
 
 var ( 
-	errBadId = errors.New("id not found") 
-	errBadCreds = errors.New("invalid entity name or password") 
-	errPerm = errors.New("permission denied") 
-	errNotLoggedIn = errors.New("not logged in") 
+	errBadId = errors.New("id not found") 
+	errBadCreds = errors.New("invalid entity name or password") 
+	errPerm = errors.New("permission denied") 
+	errNotLoggedIn = errors.New("not logged in") 
+	errUnknownWatcher = errors.New("unknown watcher id") 
+	errStoppedWatcher = errors.New("watcher has been stopped") 
 ) 
 
 var singletonErrorCodes = map[error]string{ 
@@ -41,6 +42,8 @@ 
	errBadCreds: CodeUnauthorized, 
	errPerm: CodeUnauthorized, 
	errNotLoggedIn: CodeUnauthorized, 
+	errUnknownWatcher: CodeNotFound, 
+	errStoppedWatcher: CodeStopped, 
 } 
 
 // The Code constants hold error codes for some kinds of error. 
@@ -52,15 +55,10 @@ 
	CodeExcessiveContention = "excessive contention" 
	CodeUnitHasSubordinates = "unit has subordinates" 
	CodeNotAssigned = "not assigned" 
+	CodeStopped = "stopped" 
 ) 
 
 func serverError(err error) error { 
-	err1 := serverError1(err) 
-	log.Printf("error %#v -> %#v", err, err1) 
-	return err1 
-} 
- 
-func serverError1(err error) error { 
	code := singletonErrorCodes[err] 
	switch { 
	case code != "": 
@@ -82,7 +80,7 @@ 
 // the given error, or the empty string if there 
 // is none. 
 func ErrCode(err error) string { 
-	if err := err.(rpc.ErrorCoder); err != nil { 
+	if err, _ := err.(rpc.ErrorCoder); err != nil { 
	return err.ErrorCode() 
	} 
	return "" 
@@ -91,7 +89,6 @@ 
 // clientError maps errors returned from an RPC call into local errors with 
 // appropriate values. 
 func clientError(err error) error { 
-	log.Printf("clientError %#v", err) 
	rerr, ok := err.(*rpc.ServerError) 
	if !ok { 
	return err