Function tryAcquireDistributedLease

apps/sim/lib/execution/isolated-vm.ts:347–414

(
  ownerKey: string,
  leaseId: string,
  timeoutMs: number
)

type LeaseAcquireResult = 'acquired' | 'limit_exceeded' | 'unavailable'

async function tryAcquireDistributedLease(
  ownerKey: string,
  leaseId: string,
  timeoutMs: number
): Promise<LeaseAcquireResult> {
  // Redis not configured: explicit local-mode fallback is allowed.
  if (!env.REDIS_URL) return 'acquired'

  const redis = getRedisClient()
  if (!redis) {
    logger.error('Redis is configured but unavailable for distributed lease acquisition', {
      ownerKey,
    })
    return 'unavailable'
  }

  const now = Date.now()
  const leaseTtlMs = Math.max(
    timeoutMs + QUEUE_TIMEOUT_MS + DISTRIBUTED_LEASE_GRACE_MS,
    DISTRIBUTED_LEASE_MIN_TTL_MS
  )
  const expiresAt = now + leaseTtlMs
  const key = ownerRedisKey(ownerKey)

  const script = `
    redis.call('ZREMRANGEBYSCORE', KEYS[1], '-inf', ARGV[1])
    local current = redis.call('ZCARD', KEYS[1])
    if current >= tonumber(ARGV[2]) then
      return 0
    end
    redis.call('ZADD', KEYS[1], ARGV[3], ARGV[4])
    redis.call('PEXPIRE', KEYS[1], ARGV[5])
    return 1
  `

  let deadlineTimer: NodeJS.Timeout | undefined
  const deadline = new Promise<never>((_, reject) => {
    deadlineTimer = setTimeout(
      () => reject(new Error(`Redis lease timed out after ${LEASE_REDIS_DEADLINE_MS}ms`)),
      LEASE_REDIS_DEADLINE_MS
    )
  })

  try {
    const result = await Promise.race([
      redis.eval(
        script,
        1,
        key,
        now.toString(),
        DISTRIBUTED_MAX_INFLIGHT_PER_OWNER.toString(),
        expiresAt.toString(),
        leaseId,
        leaseTtlMs.toString()
      ),
      deadline,
    ])
    return Number(result) === 1 ? 'acquired' : 'limit_exceeded'