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|
package memlimit
import (
"errors"
"fmt"
"io"
"log"
"math"
"os"
"runtime/debug"
"strconv"
)
const (
envGOMEMLIMIT = "GOMEMLIMIT"
envAUTOMEMLIMIT = "AUTOMEMLIMIT"
envAUTOMEMLIMIT_DEBUG = "AUTOMEMLIMIT_DEBUG"
defaultAUTOMEMLIMIT = 0.9
)
var (
// ErrNoLimit is returned when the memory limit is not set.
ErrNoLimit = errors.New("memory is not limited")
// ErrNoCgroup is returned when the process is not in cgroup.
ErrNoCgroup = errors.New("process is not in cgroup")
// ErrCgroupsNotSupported is returned when the system does not support cgroups.
ErrCgroupsNotSupported = errors.New("cgroups is not supported on this system")
)
type config struct {
logger *log.Logger
ratio float64
env bool
provider Provider
}
// Option is a function that configures the behavior of SetGoMemLimitWithOptions.
type Option func(cfg *config)
// WithRatio configures the ratio of the memory limit to set as GOMEMLIMIT.
//
// Default: 0.9
func WithRatio(ratio float64) Option {
return func(cfg *config) {
cfg.ratio = ratio
}
}
// WithEnv configures whether to use environment variables.
//
// Default: false
func WithEnv() Option {
return func(cfg *config) {
cfg.env = true
}
}
// WithProvider configures the provider.
//
// Default: FromCgroup
func WithProvider(provider Provider) Option {
return func(cfg *config) {
cfg.provider = provider
}
}
// SetGoMemLimitWithOpts sets GOMEMLIMIT with options.
//
// Options:
// - WithRatio
// - WithEnv (see more SetGoMemLimitWithEnv)
// - WithProvider
func SetGoMemLimitWithOpts(opts ...Option) (_ int64, _err error) {
cfg := &config{
logger: log.New(io.Discard, "", log.LstdFlags),
ratio: defaultAUTOMEMLIMIT,
env: false,
provider: FromCgroup,
}
if os.Getenv(envAUTOMEMLIMIT_DEBUG) == "true" {
cfg.logger = log.Default()
}
for _, opt := range opts {
opt(cfg)
}
defer func() {
if _err != nil {
cfg.logger.Println(_err)
}
}()
snapshot := debug.SetMemoryLimit(-1)
defer func() {
err := recover()
if err != nil {
if _err != nil {
cfg.logger.Println(_err)
}
_err = fmt.Errorf("panic during setting the Go's memory limit, rolling back to previous value %d: %v", snapshot, err)
debug.SetMemoryLimit(snapshot)
}
}()
if val, ok := os.LookupEnv(envGOMEMLIMIT); ok {
cfg.logger.Printf("GOMEMLIMIT is set already, skipping: %s\n", val)
return 0, nil
}
ratio := cfg.ratio
if val, ok := os.LookupEnv(envAUTOMEMLIMIT); ok {
if val == "off" {
cfg.logger.Printf("AUTOMEMLIMIT is set to off, skipping\n")
return 0, nil
}
_ratio, err := strconv.ParseFloat(val, 64)
if err != nil {
return 0, fmt.Errorf("cannot parse AUTOMEMLIMIT: %s", val)
}
ratio = _ratio
}
limit, err := setGoMemLimit(ApplyRatio(cfg.provider, ratio))
if err != nil {
return 0, fmt.Errorf("failed to set GOMEMLIMIT: %w", err)
}
cfg.logger.Printf("GOMEMLIMIT=%d\n", limit)
return limit, nil
}
// SetGoMemLimitWithEnv sets GOMEMLIMIT with the value from the environment variable.
// You can configure how much memory of the cgroup's memory limit to set as GOMEMLIMIT
// through AUTOMEMLIMIT in the half-open range (0.0,1.0].
//
// If AUTOMEMLIMIT is not set, it defaults to 0.9. (10% is the headroom for memory sources the Go runtime is unaware of.)
// If GOMEMLIMIT is already set or AUTOMEMLIMIT=off, this function does nothing.
func SetGoMemLimitWithEnv() {
_, _ = SetGoMemLimitWithOpts(WithEnv())
}
// SetGoMemLimit sets GOMEMLIMIT with the value from the cgroup's memory limit and given ratio.
func SetGoMemLimit(ratio float64) (int64, error) {
return SetGoMemLimitWithOpts(WithRatio(ratio))
}
// SetGoMemLimitWithProvider sets GOMEMLIMIT with the value from the given provider and ratio.
func SetGoMemLimitWithProvider(provider Provider, ratio float64) (int64, error) {
return SetGoMemLimitWithOpts(WithProvider(provider), WithRatio(ratio))
}
func setGoMemLimit(provider Provider) (int64, error) {
limit, err := provider()
if err != nil {
return 0, err
}
capped := cappedU64ToI64(limit)
debug.SetMemoryLimit(capped)
return capped, nil
}
func cappedU64ToI64(limit uint64) int64 {
if limit > math.MaxInt64 {
return math.MaxInt64
}
return int64(limit)
}
|
