change the interface

Author: sanposhiho

RATIONALE.md

@@ -223,6 +223,17 @@ result, not a parameter. The only impact would be to new plugins or those
 ported to WebAssembly. We do not expect limiting the scores to two billion
 above the valid range to be a practical concern for these authors.
 
+### Why does the Permit function return a uint32 representing milliseconds for the timeout, not `time.Duration`?
+
+`framework.PermitPlugin` returns `time.Duration` to represent the timeout.
+`time.Duration` is int64 underneath and 1 time.Duration represents 1 nanosecond.
+
+Given the scheduling throughput in the upstream kube-scheduler is around 300 pods/s, 
+that is, 3+ milliseconds per pod,
+we consider a millisecond-level timeout with uint32 to be sufficiently fine-grained.
+
+Also, tha maximum timeout is around 24 days, which also should be large enough.
+
 ## Why do we return a non-status, second numeric result as an i32?
 
 Most compilers that target WebAssembly Core Specification 1.0, the only REC

guest/api/types.go

@@ -17,8 +17,6 @@
 package api
 
 import (
-	"time"
-
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api/proto"
 )
 
@@ -130,7 +128,8 @@ type ReservePlugin interface {
 type PermitPlugin interface {
 	Plugin
 
-	Permit(state CycleState, p proto.Pod, nodeName string) (*Status, time.Duration)
+	// Note: This is uint32, not time.Duration. See /RATIONALE.md for why.
+	Permit(state CycleState, p proto.Pod, nodeName string) (status *Status, timeoutMilliSeconds uint32)
 }
 
 // PreBindPlugin is a WebAssembly implementation of framework.PreBindPlugin.

guest/internal/mem/mem.go

@@ -53,15 +53,6 @@ func BytesToPtr(b []byte) (uint32, uint32) {
 	return uint32(uintptr(ptr)), uint32(len(b))
 }
 
-// Int64ToPtr returns a pointer for the given int64 number in a way compatible
-// with WebAssembly numeric types.
-// The returned pointer aliases the number hence it must be kept alive until ptr
-// is no longer needed.
-func Int64ToPtr(n int64) uint32 {
-	ptr := unsafe.Pointer(&n)
-	return uint32(uintptr(ptr))
-}
-
 // Update is for decoding values from memory. The updater doesn't keep a
 // reference to the underlying bytes, so we don't need to copy them.
 func Update(

guest/permit/imports.go

@@ -18,12 +18,9 @@
 package permit
 
 import (
-	"runtime"
-
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/cyclestate"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/imports"
-	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/mem"
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/internal/plugin"
 )
 
@@ -42,7 +39,7 @@ var permit api.PermitPlugin
 //
 //	type permitPlugin struct{}
 //
-//	func (permitPlugin) Permit(state api.CycleState, p proto.Pod, nodeName string) (status *api.Status, timeout time.Duration)
+//	func (permitPlugin) Permit(state api.CycleState, p proto.Pod, nodeName string) (status *api.Status, timeout uint32)
 //		// Write state you need on Permit
 //	}
 func SetPlugin(permitPlugin api.PermitPlugin) {
@@ -54,12 +51,12 @@ func SetPlugin(permitPlugin api.PermitPlugin) {
 }
 
 // prevent unused lint errors (lint is run with normal go).
-var _ func() uint32 = _permit
+var _ func() uint64 = _permit
 
 // _permit is only exported to the host.
 //
 //export permit
-func _permit() uint32 {
+func _permit() uint64 {
 	if permit == nil { // Then, the user didn't define one.
 		// Unlike most plugins we always export permit so that we can reset
 		// the cycle state: return success to avoid no-op overhead.
@@ -70,9 +67,7 @@ func _permit() uint32 {
 	nodeName := imports.NodeName()
 	status, timeout := permit.Permit(cyclestate.Values, pod, nodeName)
 
-	ptr := mem.Int64ToPtr(int64(timeout))
-	setTimeoutResult(ptr)
-	runtime.KeepAlive(timeout) // untir ptr is no longer needed.
-
-	return imports.StatusToCode(status)
+	// Pack the score and status code into a single WebAssembly 1.0 compatible
+	// result
+	return (uint64(imports.StatusToCode(status)) << uint64(32)) | uint64(timeout)
 }

guest/permit/imports_stub.go

@@ -20,7 +20,6 @@ package main
 
 import (
 	"os"
-	"time"
 	"unsafe"
 
 	"sigs.k8s.io/kube-scheduler-wasm-extension/guest/api"
@@ -190,7 +189,7 @@ func (statePlugin) Unreserve(state api.CycleState, pod proto.Pod, nodeName strin
 	mustFilterState(state)
 }
 
-func (statePlugin) Permit(state api.CycleState, pod proto.Pod, nodeName string) (status *api.Status, timeout time.Duration) {
+func (statePlugin) Permit(state api.CycleState, pod proto.Pod, nodeName string) (status *api.Status, timeout uint32) {
 	mustFilterState(state)
 	return
 }

guest/permit/permit.go

@@ -35,13 +35,13 @@ func main() {
 
 type permitPlugin struct{}
 
-func (permitPlugin) Permit(state api.CycleState, pod proto.Pod, nodeName string) (*api.Status, time.Duration) {
+func (permitPlugin) Permit(state api.CycleState, pod proto.Pod, nodeName string) (*api.Status, uint32) {
 	status, timeout := api.StatusCodeSuccess, time.Duration(0)
 	if nodeName == "bad" {
 		status = api.StatusCodeError
 	} else if nodeName == "wait" {
 		status = api.StatusCodeWait
 		timeout = 10 * time.Second
 	}
-	return &api.Status{Code: status, Reason: "name is " + nodeName}, timeout
+	return &api.Status{Code: status, Reason: "name is " + nodeName}, uint32(timeout.Milliseconds())
 }