cloudflared-mirror/vendor/go.uber.org/automaxprocs/maxprocs/maxprocs.go

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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
// Package maxprocs lets Go programs easily configure runtime.GOMAXPROCS to
// match the configured Linux CPU quota. Unlike the top-level automaxprocs
// package, it lets the caller configure logging and handle errors.
package maxprocs // import "go.uber.org/automaxprocs/maxprocs"
import (
"os"
"runtime"
iruntime "go.uber.org/automaxprocs/internal/runtime"
)
const _maxProcsKey = "GOMAXPROCS"
func currentMaxProcs() int {
return runtime.GOMAXPROCS(0)
}
type config struct {
printf func(string, ...interface{})
procs func(int) (int, iruntime.CPUQuotaStatus, error)
minGOMAXPROCS int
}
func (c *config) log(fmt string, args ...interface{}) {
if c.printf != nil {
c.printf(fmt, args...)
}
}
// An Option alters the behavior of Set.
type Option interface {
apply(*config)
}
// Logger uses the supplied printf implementation for log output. By default,
// Set doesn't log anything.
func Logger(printf func(string, ...interface{})) Option {
return optionFunc(func(cfg *config) {
cfg.printf = printf
})
}
// Min sets the minimum GOMAXPROCS value that will be used.
// Any value below 1 is ignored.
func Min(n int) Option {
return optionFunc(func(cfg *config) {
if n >= 1 {
cfg.minGOMAXPROCS = n
}
})
}
type optionFunc func(*config)
func (of optionFunc) apply(cfg *config) { of(cfg) }
// Set GOMAXPROCS to match the Linux container CPU quota (if any), returning
// any error encountered and an undo function.
//
// Set is a no-op on non-Linux systems and in Linux environments without a
// configured CPU quota.
func Set(opts ...Option) (func(), error) {
cfg := &config{
procs: iruntime.CPUQuotaToGOMAXPROCS,
minGOMAXPROCS: 1,
}
for _, o := range opts {
o.apply(cfg)
}
undoNoop := func() {
cfg.log("maxprocs: No GOMAXPROCS change to reset")
}
// Honor the GOMAXPROCS environment variable if present. Otherwise, amend
// `runtime.GOMAXPROCS()` with the current process' CPU quota if the OS is
// Linux, and guarantee a minimum value of 1. The minimum guaranteed value
// can be overriden using `maxprocs.Min()`.
if max, exists := os.LookupEnv(_maxProcsKey); exists {
cfg.log("maxprocs: Honoring GOMAXPROCS=%q as set in environment", max)
return undoNoop, nil
}
maxProcs, status, err := cfg.procs(cfg.minGOMAXPROCS)
if err != nil {
return undoNoop, err
}
if status == iruntime.CPUQuotaUndefined {
cfg.log("maxprocs: Leaving GOMAXPROCS=%v: CPU quota undefined", currentMaxProcs())
return undoNoop, nil
}
prev := currentMaxProcs()
undo := func() {
cfg.log("maxprocs: Resetting GOMAXPROCS to %v", prev)
runtime.GOMAXPROCS(prev)
}
switch status {
case iruntime.CPUQuotaMinUsed:
cfg.log("maxprocs: Updating GOMAXPROCS=%v: using minimum allowed GOMAXPROCS", maxProcs)
case iruntime.CPUQuotaUsed:
cfg.log("maxprocs: Updating GOMAXPROCS=%v: determined from CPU quota", maxProcs)
}
runtime.GOMAXPROCS(maxProcs)
return undo, nil
}