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Showing 4 changed files with 128 additions and 10 deletions.
▾ src/cache/evict.ts
+24 -9
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| … | … | @@ -18,14 +18,29 @@ export async function evictAndReload(key: string) { |
| 18 | 18 | const redis = getClient(); |
| 19 | 19 | const existing = await redis.get(key); |
| 20 | 20 | if (!existing) return null; |
| 21 | // TODO: add lock before eviction to prevent races | |
| 22 | - await redis.del(key); | |
| 23 | - const fresh = await loadFromSource(key); | |
| 24 | - await redis.set(key, fresh, 'EX', 300); | |
| 25 | - return fresh; | |
| 21 | + const lease = await acquireLease(`lease:${key}`, { ttl: 5000 }); | |
| 22 | + if (!lease) { | |
| 23 | + // another worker is already rebuilding; serve stale and bail | |
| 24 | + metrics.inc('cache.evict.contended'); | |
| 25 | + return parse(existing); | |
| 26 | + } | |
| 27 | + try { | |
| 28 | + const fresh = await loadFromSource(key); | |
| 29 | + await redis.set(key, stringify(fresh), 'EX', 300); | |
| 30 | + return fresh; | |
| 31 | + } finally { | |
| 32 | + await lease.release(); | |
| 33 | + } | |
| 26 | 34 | } |
▾ src/cache/lease.ts
+38 -0
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| … | … | @@ -0,0 +1,38 @@ |
| 1 | +// Token-based lease using SET NX + unique owner id. | |
| 2 | +// Release is safe: only the owner can release their own lease. | |
| 3 | +import { randomUUID } from 'node:crypto'; | |
| 4 | +import { getClient } from './client'; | |
| 5 | + | |
| 6 | +export async function acquireLease(key: string, opts: { ttl: number }) { | |
| 7 | + const token = randomUUID(); | |
| 8 | + const ok = await getClient().set(key, token, 'PX', opts.ttl, 'NX'); | |
| 9 | + if (!ok) return null; | |
| 10 | + return { release: () => releaseLease(key, token) }; | |
| 11 | +} |
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Commits on this branch
RS
Add token-based lease around cache eviction
a1b2c3d
RS
Add race test covering 10k concurrent writes
e4f5g6h
RS
Emit metrics for contended eviction paths
i7j8k9l
loadFromSource(key)in a timeout so a slow origin doesn't hold the lease the full 5s? Even 2s would cap the blast radius on the checkout path.