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throttle.go
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throttle.go
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// Copyright 2022 Namespace Labs Inc; All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
package tasks
import (
"context"
"fmt"
"io"
"io/fs"
"os"
"sync"
"google.golang.org/protobuf/encoding/prototext"
"namespacelabs.dev/foundation/internal/environment"
"namespacelabs.dev/foundation/internal/workspace/dirs"
)
type WellKnown string
const (
WkAction = "action"
)
var (
BaseDefaultConfig = computeDefaultConfig()
baseTestConfig = []*ThrottleConfiguration{
{Labels: map[string]string{"action": "test"}, Capacity: 5},
}
)
func computeDefaultConfig() []*ThrottleConfiguration {
confs := []*ThrottleConfiguration{
{Labels: map[string]string{"action": "lowlevel.invocation"}, Capacity: 3},
{Labels: map[string]string{"action": "go.build.binary"}, Capacity: 3},
}
if !environment.IsRunningInCI() {
// This is for presentation purposes alone; so users don't see a bunch of waiting provision.invoke.
confs = append(confs, &ThrottleConfiguration{Labels: map[string]string{"action": "provision.invoke"}, Capacity: 3})
}
return confs
}
var (
_throttleKey = contextKey("fn.workspace.tasks.throttler")
)
type throttleState struct {
mu sync.Mutex
cond *sync.Cond
capacity []*throttleCapacity
}
const marker = "-"
type throttleCapacity struct {
c *ThrottleConfiguration
used map[string]int32 // Total amount of capacity used per value.
}
func LoadThrottlerConfig(ctx context.Context, debugLog io.Writer) *ThrottleConfigurations {
if dir, err := dirs.Config(); err == nil {
if cfg, err := parseThrottleConfigFrom(os.DirFS(dir)); err == nil {
fmt.Fprintf(debugLog, "Using user-provided throttle configuration (loaded from %s).\n", dir)
return cfg
}
}
configs := &ThrottleConfigurations{}
configs.ThrottleConfiguration = append(configs.ThrottleConfiguration, BaseDefaultConfig...)
configs.ThrottleConfiguration = append(configs.ThrottleConfiguration, baseTestConfig...)
return configs
}
func ContextWithThrottler(ctx context.Context, debugLog io.Writer, confs *ThrottleConfigurations) context.Context {
return context.WithValue(ctx, _throttleKey, newThrottleState(debugLog, confs.ThrottleConfiguration))
}
func throttlerFromContext(ctx context.Context) *throttleState {
if s, ok := ctx.Value(_throttleKey).(*throttleState); ok {
return s
}
return nil
}
func parseThrottleConfigFrom(fsys fs.FS) (*ThrottleConfigurations, error) {
bytes, err := fs.ReadFile(fsys, "throttle.textpb")
if err != nil {
return nil, err
}
confs := &ThrottleConfigurations{}
if err := prototext.Unmarshal(bytes, confs); err != nil {
return nil, err
}
return confs, nil
}
func newThrottleState(debug io.Writer, confs []*ThrottleConfiguration) *throttleState {
fmt.Fprintln(debug, "Setting up action throttler.")
ts := &throttleState{}
ts.cond = sync.NewCond(&ts.mu)
for _, conf := range confs {
ts.capacity = append(ts.capacity, &throttleCapacity{c: conf, used: map[string]int32{}})
fmt.Fprintf(debug, " %+v\n", conf)
}
return ts
}
func (ts *throttleState) AcquireLease(ctx context.Context, wellKnown map[WellKnown]string) (func(), error) {
if ts == nil {
return nil, nil
}
ts.mu.Lock()
defer ts.mu.Unlock()
for {
var needsCap bool
var incs, decs []func()
for _, cap := range ts.capacity {
cap := cap // Capture cap.
if !cap.matches(wellKnown) {
continue
}
var label string
if cap.c.CountPerLabel != "" {
var ok bool
label, ok = wellKnown[WellKnown(cap.c.CountPerLabel)]
if !ok {
continue
}
} else {
label = marker
}
if v, ok := cap.used[label]; !ok || v < cap.c.Capacity {
incs = append(incs, func() {
cap.used[label]++
})
decs = append(decs, func() {
cap.used[label]--
})
} else {
needsCap = true
}
}
if err := ctx.Err(); err != nil {
return nil, err
}
if !needsCap {
for _, inc := range incs {
inc()
}
return func() {
ts.mu.Lock()
for _, dec := range decs {
dec()
}
ts.cond.Broadcast()
ts.mu.Unlock()
}, nil
}
ts.cond.Wait()
}
}
func (tc *throttleCapacity) matches(labels map[WellKnown]string) bool {
for key, value := range tc.c.Labels {
if chk, ok := labels[WellKnown(key)]; !ok || chk != value {
return false
}
}
return true
}