replication: refactor driving logic (no more explicit state machine)

replication/report/replication_report.go

@@ -0,0 +1,150 @@
+package report
+
+import (
+	"encoding/json"
+	"time"
+)
+
+type Report struct {
+	StartAt, FinishAt time.Time
+	Attempts          []*AttemptReport
+}
+
+var _, _ = json.Marshal(&Report{})
+
+type TimedError struct {
+	Err  string
+	Time time.Time
+}
+
+func NewTimedError(err string, t time.Time) *TimedError {
+	if err == "" {
+		panic("error must be empty")
+	}
+	if t.IsZero() {
+		panic("t must be non-zero")
+	}
+	return &TimedError{err, t}
+}
+
+func (s *TimedError) Error() string {
+	return s.Err
+}
+
+var _, _ = json.Marshal(&TimedError{})
+
+type AttemptReport struct {
+	State             AttemptState
+	StartAt, FinishAt time.Time
+	PlanError         *TimedError
+	Filesystems       []*FilesystemReport
+}
+
+type AttemptState string
+
+const (
+	AttemptPlanning      AttemptState = "planning"
+	AttemptPlanningError AttemptState = "planning-error"
+	AttemptFanOutFSs     AttemptState = "fan-out-filesystems"
+	AttemptFanOutError   AttemptState = "filesystem-error"
+	AttemptDone          AttemptState = "done"
+)
+
+type FilesystemState string
+
+const (
+	FilesystemPlanning        FilesystemState = "planning"
+	FilesystemPlanningErrored FilesystemState = "planning-error"
+	FilesystemStepping        FilesystemState = "stepping"
+	FilesystemSteppingErrored FilesystemState = "step-error"
+	FilesystemDone            FilesystemState = "done"
+)
+
+type FilesystemReport struct {
+	Info *FilesystemInfo
+
+	State FilesystemState
+
+	// Valid in State = FilesystemPlanningErrored
+	PlanError *TimedError
+	// Valid in State = FilesystemSteppingErrored
+	StepError *TimedError
+
+	// Valid in State = FilesystemStepping
+	CurrentStep int
+	Steps       []*StepReport
+}
+
+type FilesystemInfo struct {
+	Name string
+}
+
+type StepReport struct {
+	Info *StepInfo
+}
+
+type StepInfo struct {
+	From, To        string
+	BytesExpected   int64
+	BytesReplicated int64
+}
+
+func (a *AttemptReport) BytesSum() (expected, replicated int64) {
+	for _, fs := range a.Filesystems {
+		e, r := fs.BytesSum()
+		expected += e
+		replicated += r
+	}
+	return expected, replicated
+}
+
+func (f *FilesystemReport) BytesSum() (expected, replicated int64) {
+	for _, step := range f.Steps {
+		expected += step.Info.BytesExpected
+		replicated += step.Info.BytesReplicated
+	}
+	return
+}
+
+func (f *AttemptReport) FilesystemsByState() map[FilesystemState][]*FilesystemReport {
+	r := make(map[FilesystemState][]*FilesystemReport, 4)
+	for _, fs := range f.Filesystems {
+		l := r[fs.State]
+		l = append(l, fs)
+		r[fs.State] = l
+	}
+	return r
+}
+
+func (f *FilesystemReport) Error() *TimedError {
+	switch f.State {
+	case FilesystemPlanningErrored:
+		return f.PlanError
+	case FilesystemSteppingErrored:
+		return f.StepError
+	}
+	return nil
+}
+
+// may return nil
+func (f *FilesystemReport) NextStep() *StepReport {
+	switch f.State {
+	case FilesystemDone:
+		return nil
+	case FilesystemPlanningErrored:
+		return nil
+	case FilesystemSteppingErrored:
+		return nil
+	case FilesystemPlanning:
+		return nil
+	case FilesystemStepping:
+		// invariant is that this is always correct
+		// TODO what about 0-length Steps but short intermediary state?
+		return f.Steps[f.CurrentStep]
+	}
+	panic("unreachable")
+}
+
+func (f *StepReport) IsIncremental() bool {
+	return f.Info.From != "" // FIXME change to ZFS semantics (To != "")
+}