[feature] Inherit resource limits from cgroups (#1336)

When GTS is running in a container runtime which has configured CPU or
memory limits or under an init system that uses cgroups to impose CPU
and memory limits the values the Go runtime sees for GOMAXPROCS and
GOMEMLIMIT are still based on the host resources, not the cgroup.

At least for the throttling middlewares which use GOMAXPROCS to
configure their queue size, this can result in GTS running with values
too big compared to the resources that will actuall be available to it.

This introduces 2 dependencies which can pick up resource contraints
from the current cgroup and tune the Go runtime accordingly. This should
result in the different queues being appropriately sized and in general
more predictable performance. These dependencies are a no-op on
non-Linux systems or if running in a cgroup that doesn't set a limit on
CPU or memory.

The automatic tuning of GOMEMLIMIT can be disabled by either explicitly
setting GOMEMLIMIT yourself or by setting AUTOMEMLIMIT=off. The
automatic tuning of GOMAXPROCS can similarly be counteracted by setting
GOMAXPROCS yourself.

1 files changed, 284 insertions, 0 deletions

diff --git a/vendor/github.com/godbus/dbus/v5/variant_lexer.go b/vendor/github.com/godbus/dbus/v5/variant_lexer.go
new file mode 100644
index 000000000..bf1398c8f
--- /dev/null
+++ b/vendor/github.com/godbus/dbus/v5/variant_lexer.go
@@ -0,0 +1,284 @@
+package dbus
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Heavily inspired by the lexer from text/template.
+
+type varToken struct {
+	typ varTokenType
+	val string
+}
+
+type varTokenType byte
+
+const (
+	tokEOF varTokenType = iota
+	tokError
+	tokNumber
+	tokString
+	tokBool
+	tokArrayStart
+	tokArrayEnd
+	tokDictStart
+	tokDictEnd
+	tokVariantStart
+	tokVariantEnd
+	tokComma
+	tokColon
+	tokType
+	tokByteString
+)
+
+type varLexer struct {
+	input  string
+	start  int
+	pos    int
+	width  int
+	tokens []varToken
+}
+
+type lexState func(*varLexer) lexState
+
+func varLex(s string) []varToken {
+	l := &varLexer{input: s}
+	l.run()
+	return l.tokens
+}
+
+func (l *varLexer) accept(valid string) bool {
+	if strings.ContainsRune(valid, l.next()) {
+		return true
+	}
+	l.backup()
+	return false
+}
+
+func (l *varLexer) backup() {
+	l.pos -= l.width
+}
+
+func (l *varLexer) emit(t varTokenType) {
+	l.tokens = append(l.tokens, varToken{t, l.input[l.start:l.pos]})
+	l.start = l.pos
+}
+
+func (l *varLexer) errorf(format string, v ...interface{}) lexState {
+	l.tokens = append(l.tokens, varToken{
+		tokError,
+		fmt.Sprintf(format, v...),
+	})
+	return nil
+}
+
+func (l *varLexer) ignore() {
+	l.start = l.pos
+}
+
+func (l *varLexer) next() rune {
+	var r rune
+
+	if l.pos >= len(l.input) {
+		l.width = 0
+		return -1
+	}
+	r, l.width = utf8.DecodeRuneInString(l.input[l.pos:])
+	l.pos += l.width
+	return r
+}
+
+func (l *varLexer) run() {
+	for state := varLexNormal; state != nil; {
+		state = state(l)
+	}
+}
+
+func (l *varLexer) peek() rune {
+	r := l.next()
+	l.backup()
+	return r
+}
+
+func varLexNormal(l *varLexer) lexState {
+	for {
+		r := l.next()
+		switch {
+		case r == -1:
+			l.emit(tokEOF)
+			return nil
+		case r == '[':
+			l.emit(tokArrayStart)
+		case r == ']':
+			l.emit(tokArrayEnd)
+		case r == '{':
+			l.emit(tokDictStart)
+		case r == '}':
+			l.emit(tokDictEnd)
+		case r == '<':
+			l.emit(tokVariantStart)
+		case r == '>':
+			l.emit(tokVariantEnd)
+		case r == ':':
+			l.emit(tokColon)
+		case r == ',':
+			l.emit(tokComma)
+		case r == '\'' || r == '"':
+			l.backup()
+			return varLexString
+		case r == '@':
+			l.backup()
+			return varLexType
+		case unicode.IsSpace(r):
+			l.ignore()
+		case unicode.IsNumber(r) || r == '+' || r == '-':
+			l.backup()
+			return varLexNumber
+		case r == 'b':
+			pos := l.start
+			if n := l.peek(); n == '"' || n == '\'' {
+				return varLexByteString
+			}
+			// not a byte string; try to parse it as a type or bool below
+			l.pos = pos + 1
+			l.width = 1
+			fallthrough
+		default:
+			// either a bool or a type. Try bools first.
+			l.backup()
+			if l.pos+4 <= len(l.input) {
+				if l.input[l.pos:l.pos+4] == "true" {
+					l.pos += 4
+					l.emit(tokBool)
+					continue
+				}
+			}
+			if l.pos+5 <= len(l.input) {
+				if l.input[l.pos:l.pos+5] == "false" {
+					l.pos += 5
+					l.emit(tokBool)
+					continue
+				}
+			}
+			// must be a type.
+			return varLexType
+		}
+	}
+}
+
+var varTypeMap = map[string]string{
+	"boolean":    "b",
+	"byte":       "y",
+	"int16":      "n",
+	"uint16":     "q",
+	"int32":      "i",
+	"uint32":     "u",
+	"int64":      "x",
+	"uint64":     "t",
+	"double":     "f",
+	"string":     "s",
+	"objectpath": "o",
+	"signature":  "g",
+}
+
+func varLexByteString(l *varLexer) lexState {
+	q := l.next()
+Loop:
+	for {
+		switch l.next() {
+		case '\\':
+			if r := l.next(); r != -1 {
+				break
+			}
+			fallthrough
+		case -1:
+			return l.errorf("unterminated bytestring")
+		case q:
+			break Loop
+		}
+	}
+	l.emit(tokByteString)
+	return varLexNormal
+}
+
+func varLexNumber(l *varLexer) lexState {
+	l.accept("+-")
+	digits := "0123456789"
+	if l.accept("0") {
+		if l.accept("x") {
+			digits = "0123456789abcdefABCDEF"
+		} else {
+			digits = "01234567"
+		}
+	}
+	for strings.ContainsRune(digits, l.next()) {
+	}
+	l.backup()
+	if l.accept(".") {
+		for strings.ContainsRune(digits, l.next()) {
+		}
+		l.backup()
+	}
+	if l.accept("eE") {
+		l.accept("+-")
+		for strings.ContainsRune("0123456789", l.next()) {
+		}
+		l.backup()
+	}
+	if r := l.peek(); unicode.IsLetter(r) {
+		l.next()
+		return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
+	}
+	l.emit(tokNumber)
+	return varLexNormal
+}
+
+func varLexString(l *varLexer) lexState {
+	q := l.next()
+Loop:
+	for {
+		switch l.next() {
+		case '\\':
+			if r := l.next(); r != -1 {
+				break
+			}
+			fallthrough
+		case -1:
+			return l.errorf("unterminated string")
+		case q:
+			break Loop
+		}
+	}
+	l.emit(tokString)
+	return varLexNormal
+}
+
+func varLexType(l *varLexer) lexState {
+	at := l.accept("@")
+	for {
+		r := l.next()
+		if r == -1 {
+			break
+		}
+		if unicode.IsSpace(r) {
+			l.backup()
+			break
+		}
+	}
+	if at {
+		if _, err := ParseSignature(l.input[l.start+1 : l.pos]); err != nil {
+			return l.errorf("%s", err)
+		}
+	} else {
+		if _, ok := varTypeMap[l.input[l.start:l.pos]]; ok {
+			l.emit(tokType)
+			return varLexNormal
+		}
+		return l.errorf("unrecognized type %q", l.input[l.start:l.pos])
+	}
+	l.emit(tokType)
+	return varLexNormal
+}