chore: import upstream snapshot with attribution

apps/sim/lib/concurrency/leader-lock.ts

@@ -0,0 +1,73 @@
+import { createLogger } from '@sim/logger'
+import { toError } from '@sim/utils/errors'
+import { sleep } from '@sim/utils/helpers'
+import { generateShortId } from '@sim/utils/id'
+import { acquireLock, releaseLock } from '@/lib/core/config/redis'
+
+const logger = createLogger('LeaderLock')
+
+const DEFAULT_TTL_SEC = 10
+const DEFAULT_POLL_INTERVAL_MS = 100
+const DEFAULT_MAX_WAIT_MS = 3_000
+
+export interface LeaderLockOptions<T> {
+  key: string
+  ttlSec?: number
+  pollIntervalMs?: number
+  maxWaitMs?: number
+  onLeader: () => Promise<T | null>
+  onFollower: () => Promise<T | null>
+}
+
+export async function withLeaderLock<T>(opts: LeaderLockOptions<T>): Promise<T | null> {
+  const {
+    key,
+    ttlSec = DEFAULT_TTL_SEC,
+    pollIntervalMs = DEFAULT_POLL_INTERVAL_MS,
+    maxWaitMs = DEFAULT_MAX_WAIT_MS,
+    onLeader,
+    onFollower,
+  } = opts
+
+  const ownerToken = generateShortId()
+
+  let acquired = false
+  try {
+    acquired = await acquireLock(key, ownerToken, ttlSec)
+  } catch (error) {
+    logger.warn('Lock acquisition failed; running leader path uncoordinated', {
+      key,
+      error: toError(error).message,
+    })
+    return onLeader()
+  }
+
+  if (acquired) {
+    try {
+      return await onLeader()
+    } finally {
+      try {
+        await releaseLock(key, ownerToken)
+      } catch (error) {
+        logger.warn('Lock release failed (will expire via TTL)', {
+          key,
+          error: toError(error).message,
+        })
+      }
+    }
+  }
+
+  const deadline = Date.now() + maxWaitMs
+  while (Date.now() < deadline) {
+    await sleep(pollIntervalMs)
+    const value = await onFollower()
+    if (value !== null) return value
+  }
+
+  // The leader may have persisted between our final poll and now; one last check.
+  const lastChance = await onFollower()
+  if (lastChance !== null) return lastChance
+
+  logger.warn('Follower timed out waiting for leader', { key, maxWaitMs })
+  return null
+}