Safe Haskell	None
Language	GHC2021

Ecluse.Core.Server.Admission.Budget

Contents

Charges
Decisions

Description

The arithmetic of the metadata memory budget: what a byte count costs, how many steps cover a shortfall, and which request the meter lets move. Ecluse.Core.Server.Admission.Meter applies these decisions inside its transactions.

Synopsis

scaleCharge :: Int -> Int -> Int
roundUpToStep :: Int -> Int -> Int
data MeterView = MeterView {
- mvBudget :: Int
- mvCharged :: Int
- mvToken :: Maybe Int
- mvOldestWaiter :: Maybe Int
}
data EntryGate
- = EntryAdmit
- | EntryQueue
- | EntryRefuse
entryDecision :: MeterView -> Int -> Int -> Int -> EntryGate
entryReady :: MeterView -> Int -> Bool
data GrowthGate
- = GrowWithin
- | GrowOnToken
- | GrowTakeToken
- | GrowWait
growthDecision :: MeterView -> IntSet -> Int -> GrowthGate

Charges

scaleCharge :: Int -> Int -> Int Source #

The charge for a byte count, rounded up, so a non-empty read never costs nothing.

roundUpToStep :: Int -> Int -> Int Source #

The smallest whole number of steps that covers a shortfall, in bytes.

Decisions

data MeterView Source #

What a meter transaction reads before it decides.

Constructors

MeterView
Fields mvBudget :: Int mvCharged :: Int mvToken :: Maybe Int The ticket that holds the overdraw token, if any. mvOldestWaiter :: Maybe Int The oldest ticket paused on a growth step or waiting on the work of one, if any.

Instances

Instances details

Show MeterView Source #
Instance details Defined in Ecluse.Core.Server.Admission.Budget Methods showsPrec :: Int -> MeterView -> ShowS # show :: MeterView -> String # showList :: [MeterView] -> ShowS #
Eq MeterView Source #
Instance details Defined in Ecluse.Core.Server.Admission.Budget Methods (==) :: MeterView -> MeterView -> Bool # (/=) :: MeterView -> MeterView -> Bool #

data EntryGate Source #

The gate's answer to a new request.

Constructors

EntryAdmit	The entry step fits now.
EntryQueue	Wait for the step, up to the admission wait.
EntryRefuse	The waiting room is full: shed at once.

Instances

Instances details

Show EntryGate Source #
Instance details Defined in Ecluse.Core.Server.Admission.Budget Methods showsPrec :: Int -> EntryGate -> ShowS # show :: EntryGate -> String # showList :: [EntryGate] -> ShowS #
Eq EntryGate Source #
Instance details Defined in Ecluse.Core.Server.Admission.Budget Methods (==) :: EntryGate -> EntryGate -> Bool # (/=) :: EntryGate -> EntryGate -> Bool #

entryDecision :: MeterView -> Int -> Int -> Int -> EntryGate Source #

New work takes its entry step only when it fits, nobody queued before it, and no started read is paused. A paused read always has the prior claim on freed memory.

entryReady :: MeterView -> Int -> Bool Source #

Whether a queued request may take its entry step now.

data GrowthGate Source #

The answer to a started request that needs more bytes.

Constructors

GrowWithin	The step fits within the budget.
GrowOnToken	The step does not fit, but it serves the ticket that holds the overdraw token.
GrowTakeToken	The step does not fit, the token is free, and this charge serves the oldest paused ticket.
GrowWait	Pause until memory frees.

Instances

Instances details

Show GrowthGate Source #
Instance details Defined in Ecluse.Core.Server.Admission.Budget Methods showsPrec :: Int -> GrowthGate -> ShowS # show :: GrowthGate -> String # showList :: [GrowthGate] -> ShowS #
Eq GrowthGate Source #
Instance details Defined in Ecluse.Core.Server.Admission.Budget Methods (==) :: GrowthGate -> GrowthGate -> Bool # (/=) :: GrowthGate -> GrowthGate -> Bool #

growthDecision :: MeterView -> IntSet -> Int -> GrowthGate Source #

A step that fits proceeds. Past the budget, only work serving the token holder moves, or with a free token, work serving the oldest paused ticket. served: the charging ticket and those waiting on it.