Safe Haskell	None
Language	GHC2021

Ecluse.Core.Worker.Lease

Contents

The controller
The transport, clock, and pacing it runs on
Renewal arithmetic

Description

Holding every received receipt for as long as the worker needs it.

A backend hides a delivery for one window (Ecluse.Core.Queue.Lease). A batch runs sequentially, so a receipt waiting its turn and a receipt whose job runs long both outlive that window and would be redelivered to a second consumer. The controller renews each one from receipt until its disposition, and a renewal and a disposition never overlap on the same receipt. A receipt whose lease cannot be kept is dropped alone and left unacknowledged.

Synopsis

data LeasedReceipt
leasedMessage :: LeasedReceipt -> QueueMessage
withLeasedBatch :: (MonadUnliftIO m, KatipContext m) => LeaseOps -> [QueueMessage] -> ([LeasedReceipt] -> m a) -> m a
whileLeased :: MonadUnliftIO m => LeasedReceipt -> m a -> m (Maybe a)
disposing :: MonadUnliftIO m => LeasedReceipt -> m a -> m a
data LeaseOps = LeaseOps {
- loRenew :: ReceiptHandle -> Seconds -> IO (Either TransportFault ())
- loNow :: IO MonoTime
- loWaitUntil :: MonoTime -> IO ()
- loRetryDelays :: [Int]
}
queueLeaseOps :: MirrorQueue -> LeaseOps
leaseRenewAt :: MonoTime -> MonoTime -> MonoTime
leaseRetryUntil :: Seconds -> MonoTime -> MonoTime
leaseRequest :: ReceiptLease -> MonoTime -> Maybe Seconds

The controller

data LeasedReceipt Source #

One received receipt and the lease held over it. A renewal task runs per leased receipt, so a batch runs at most ten of them beside its single artifact task.

leasedMessage :: LeasedReceipt -> QueueMessage Source #

The message this receipt delivered.

withLeasedBatch :: (MonadUnliftIO m, KatipContext m) => LeaseOps -> [QueueMessage] -> ([LeasedReceipt] -> m a) -> m a Source #

Lease every receipt in a batch for the body's whole run, renewing each continually. Leaving the body cancels every renewal, so an unfinished receipt stays unacknowledged.

whileLeased :: MonadUnliftIO m => LeasedReceipt -> m a -> m (Maybe a) Source #

Run this receipt's work while its lease holds, cancelling the work the moment the lease is dropped. Nothing says the receipt was dropped, so nothing was decided for it.

disposing :: MonadUnliftIO m => LeasedReceipt -> m a -> m a Source #

Realise a receipt's disposition with its renewal stopped first, so none can follow an acknowledgement, a release for retry, or a terminal backoff.

The transport, clock, and pacing it runs on

data LeaseOps Source #

The transport, clock, and pacing a lease runs on, injected so a test drives renewal on a clock it controls rather than on real time.

Constructors

LeaseOps

Fields

loRenew :: ReceiptHandle -> Seconds -> IO (Either TransportFault ())
Reset one receipt's visibility window to the given duration.
loNow :: IO MonoTime
The monotonic clock every lease deadline is measured on.
loWaitUntil :: MonoTime -> IO ()
Wait until the given instant. It takes the instant, not a duration, so several waits running at once cannot each push a shared test clock on by their own full pause.
loRetryDelays :: [Int]
The pacing between renewal attempts, in microseconds. Its length is the retry budget, and a retry stops early once the receipt's own margin runs out.

queueLeaseOps :: MirrorQueue -> LeaseOps Source #

The lease transport over a live queue handle, at the shipped clock and pacing.

Renewal arithmetic

leaseRenewAt :: MonoTime -> MonoTime -> MonoTime Source #

When a held lease is renewed: a third of the way into what is left of it, so two renewals can fail before the window lapses.

leaseRetryUntil :: Seconds -> MonoTime -> MonoTime Source #

The last instant a renewal may be sent: a tenth of the window before the deadline, the transport margin a request needs to land while the lease still holds.

leaseRequest :: ReceiptLease -> MonoTime -> Maybe Seconds Source #

The window a renewal asks for: the one the backend granted, clipped to what is left before its ceiling from receipt. Nothing once under a second is left, which drops the receipt.