feat: two-phase rename for path collision safety #78
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,129 @@ | ||
| package main | ||
|
|
||
| import ( | ||
| "errors" | ||
| "fmt" | ||
| "log" | ||
| "os" | ||
| "path/filepath" | ||
| "sort" | ||
| ) | ||
|
|
||
| type renamePlan struct { | ||
| from string | ||
| to string | ||
| temp string | ||
| } | ||
|
|
||
| func (fr *findReplace) queueRename(from, to string) { | ||
| fr.renameMu.Lock() | ||
| fr.renames = append(fr.renames, renamePlan{from: from, to: to}) | ||
| fr.renameMu.Unlock() | ||
| } | ||
|
|
||
| func (fr *findReplace) applyRenames() error { | ||
| if len(fr.renames) == 0 { | ||
| return nil | ||
| } | ||
|
|
||
| active := make([]renamePlan, 0, len(fr.renames)) | ||
| sources := make(map[string]bool, len(fr.renames)) | ||
| targets := make(map[string]bool, len(fr.renames)) | ||
| for _, r := range fr.renames { | ||
| if r.from == r.to { | ||
| continue | ||
| } | ||
| if targets[r.to] { | ||
| return fmt.Errorf("duplicate rename target %q", r.to) | ||
| } | ||
| active = append(active, r) | ||
| sources[r.from] = true | ||
| targets[r.to] = true | ||
| } | ||
|
|
||
| if len(active) == 0 { | ||
| return nil | ||
| } | ||
|
|
||
| needsTwoPhase := false | ||
| for _, r := range active { | ||
| if sources[r.to] { | ||
| needsTwoPhase = true | ||
| break | ||
| } | ||
| } | ||
|
|
||
| sort.Slice(active, func(i, j int) bool { | ||
| if len(active[i].from) != len(active[j].from) { | ||
| return len(active[i].from) > len(active[j].from) | ||
| } | ||
| return active[i].from < active[j].from | ||
| }) | ||
|
|
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| if needsTwoPhase { | ||
| return fr.applyRenamesTwoPhase(active) | ||
| } | ||
| return fr.applyRenamesDirect(active) | ||
| } | ||
|
|
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| func (fr *findReplace) applyRenamesDirect(plans []renamePlan) error { | ||
| var errs []error | ||
| for _, r := range plans { | ||
| if err := fr.renamePath(r.from, r.to); err != nil { | ||
| errs = append(errs, err) | ||
| } | ||
| } | ||
| return errors.Join(errs...) | ||
| } | ||
|
|
||
| func (fr *findReplace) applyRenamesTwoPhase(plans []renamePlan) error { | ||
| rollback := func() { | ||
| for _, r := range plans { | ||
| if r.temp != "" { | ||
| _ = os.Remove(r.temp) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| seq := 0 | ||
| for i := range plans { | ||
| r := &plans[i] | ||
| r.temp = filepath.Join(filepath.Dir(r.from), fmt.Sprintf(".find-replace.tmp.%d.%d", os.Getpid(), seq)) | ||
| seq++ | ||
| log.Printf("Renaming %v to %v (phase 1)", r.from, filepath.Base(r.temp)) | ||
| if err := os.Rename(r.from, r.temp); err != nil { | ||
| rollback() | ||
| return fmt.Errorf("phase 1 rename %q: %w", r.from, err) | ||
| } | ||
| } | ||
|
|
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| phase2 := append([]renamePlan(nil), plans...) | ||
| sort.Slice(phase2, func(i, j int) bool { | ||
| if len(phase2[i].to) != len(phase2[j].to) { | ||
| return len(phase2[i].to) > len(phase2[j].to) | ||
| } | ||
| return phase2[i].to < phase2[j].to | ||
| }) | ||
|
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| for _, r := range phase2 { | ||
| log.Printf("Renaming %v to %v (phase 2)", filepath.Base(r.temp), filepath.Base(r.to)) | ||
| if err := os.Rename(r.temp, r.to); err != nil { | ||
|
There was a problem hiding this comment.
When any source/target chain triggers the two-phase path, phase 2 uses raw Useful? React with 👍 / 👎. |
||
| return fmt.Errorf("phase 2 rename %q -> %q: %w", r.temp, r.to, err) | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
|
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| func (fr *findReplace) renamePath(from, to string) error { | ||
| if _, err := os.Stat(to); err == nil { | ||
| return fmt.Errorf("refusing to rename %v to %v: %v already exists", from, filepath.Base(to), to) | ||
| } else if !errors.Is(err, os.ErrNotExist) { | ||
| return fmt.Errorf("stat rename destination %v: %w", to, err) | ||
| } | ||
|
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| log.Printf("Renaming %v to %v", from, filepath.Base(to)) | ||
| if err := os.Rename(from, to); err != nil { | ||
| return fmt.Errorf("rename %v to %v: %w", from, filepath.Base(to), err) | ||
| } | ||
| return nil | ||
| } | ||
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The phase-1 temp is created inside the source's parent directory, so a descendant rename can be invalidated when an ancestor directory is also renamed later in the same two-phase batch. For example,
find-replace a aawith a directorya/containing fileaand a siblingaa/queues botha/a -> a/aaanda -> aa; phase 1 movesa/atoa/.find-replace.tmp..., then movesaitself, so phase 2 later looks for the child temp at the olda/...path and fails, leaving data stranded in the directory temp.Useful? React with 👍 / 👎.