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