| 1 | package agent |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "sync" |
| 6 | ) |
| 7 | |
| 8 | // compactionGate is a zero-value, cancellation-aware single-flight latch. |
| 9 | type compactionGate struct { |
| 10 | once sync.Once |
| 11 | token chan struct{} |
| 12 | } |
| 13 | |
| 14 | func (g *compactionGate) acquire(ctx context.Context) error { |
| 15 | g.once.Do(func() { g.token = make(chan struct{}, 1) }) |
| 16 | if err := ctx.Err(); err != nil { |
| 17 | return err |
| 18 | } |
| 19 | select { |
| 20 | case g.token <- struct{}{}: |
| 21 | return g.acquired(ctx) |
| 22 | case <-ctx.Done(): |
| 23 | return ctx.Err() |
| 24 | } |
| 25 | } |
| 26 | |
| 27 | func (g *compactionGate) acquired(ctx context.Context) error { |
| 28 | if err := ctx.Err(); err != nil { |
| 29 | g.Unlock() |
| 30 | return err |
| 31 | } |
| 32 | return nil |
| 33 | } |
| 34 | |
| 35 | func (g *compactionGate) Lock() { _ = g.acquire(context.Background()) } |
| 36 | func (g *compactionGate) Unlock() { <-g.token } |
| 37 |