Update vendor before 0.16.0 (#829)

* Update vendor github.com/coreos/go-systemd/dbus@v16

* Update vendor github.com/golang/protobuf/proto@v1.0.0

* Update vendor github.com/prometheus/...

* Update vendor golang.org/x/...

vendor/github.com/coreos/go-systemd/NOTICE

@@ -0,0 +1,5 @@
+CoreOS Project
+Copyright 2018 CoreOS, Inc
+
+This product includes software developed at CoreOS, Inc.
+(http://www.coreos.com/).

vendor/github.com/coreos/go-systemd/dbus/dbus.go

@@ -16,6 +16,7 @@
 package dbus
 
 import (
+	"encoding/hex"
 	"fmt"
 	"os"
 	"strconv"
@@ -60,6 +61,27 @@ func PathBusEscape(path string) string {
 	return string(n)
 }
 
+// pathBusUnescape is the inverse of PathBusEscape.
+func pathBusUnescape(path string) string {
+	if path == "_" {
+		return ""
+	}
+	n := []byte{}
+	for i := 0; i < len(path); i++ {
+		c := path[i]
+		if c == '_' && i+2 < len(path) {
+			res, err := hex.DecodeString(path[i+1 : i+3])
+			if err == nil {
+				n = append(n, res...)
+			}
+			i += 2
+		} else {
+			n = append(n, c)
+		}
+	}
+	return string(n)
+}
+
 // Conn is a connection to systemd's dbus endpoint.
 type Conn struct {
 	// sysconn/sysobj are only used to call dbus methods
@@ -74,13 +96,18 @@ type Conn struct {
 		jobs map[dbus.ObjectPath]chan<- string
 		sync.Mutex
 	}
-	subscriber struct {
+	subStateSubscriber struct {
 		updateCh chan<- *SubStateUpdate
 		errCh    chan<- error
 		sync.Mutex
 		ignore      map[dbus.ObjectPath]int64
 		cleanIgnore int64
 	}
+	propertiesSubscriber struct {
+		updateCh chan<- *PropertiesUpdate
+		errCh    chan<- error
+		sync.Mutex
+	}
 }
 
 // New establishes a connection to any available bus and authenticates.
@@ -152,7 +179,7 @@ func NewConnection(dialBus func() (*dbus.Conn, error)) (*Conn, error) {
 		sigobj:  systemdObject(sigconn),
 	}
 
-	c.subscriber.ignore = make(map[dbus.ObjectPath]int64)
+	c.subStateSubscriber.ignore = make(map[dbus.ObjectPath]int64)
 	c.jobListener.jobs = make(map[dbus.ObjectPath]chan<- string)
 
 	// Setup the listeners on jobs so that we can get completions

vendor/github.com/coreos/go-systemd/dbus/methods.go

@@ -1,4 +1,4 @@
-// Copyright 2015 CoreOS, Inc.
+// Copyright 2015, 2018 CoreOS, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@ package dbus
 
 import (
 	"errors"
+	"fmt"
 	"path"
 	"strconv"
 
@@ -148,14 +149,27 @@ func (c *Conn) ResetFailedUnit(name string) error {
 	return c.sysobj.Call("org.freedesktop.systemd1.Manager.ResetFailedUnit", 0, name).Store()
 }
 
-// getProperties takes the unit name and returns all of its dbus object properties, for the given dbus interface
-func (c *Conn) getProperties(unit string, dbusInterface string) (map[string]interface{}, error) {
+// SystemState returns the systemd state. Equivalent to `systemctl is-system-running`.
+func (c *Conn) SystemState() (*Property, error) {
+	var err error
+	var prop dbus.Variant
+
+	obj := c.sysconn.Object("org.freedesktop.systemd1", "/org/freedesktop/systemd1")
+	err = obj.Call("org.freedesktop.DBus.Properties.Get", 0, "org.freedesktop.systemd1.Manager", "SystemState").Store(&prop)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Property{Name: "SystemState", Value: prop}, nil
+}
+
+// getProperties takes the unit path and returns all of its dbus object properties, for the given dbus interface
+func (c *Conn) getProperties(path dbus.ObjectPath, dbusInterface string) (map[string]interface{}, error) {
 	var err error
 	var props map[string]dbus.Variant
 
-	path := unitPath(unit)
 	if !path.IsValid() {
-		return nil, errors.New("invalid unit name: " + unit)
+		return nil, fmt.Errorf("invalid unit name: %v", path)
 	}
 
 	obj := c.sysconn.Object("org.freedesktop.systemd1", path)
@@ -172,9 +186,15 @@ func (c *Conn) getProperties(unit string, dbusInterface string) (map[string]inte
 	return out, nil
 }
 
-// GetUnitProperties takes the unit name and returns all of its dbus object properties.
+// GetUnitProperties takes the (unescaped) unit name and returns all of its dbus object properties.
 func (c *Conn) GetUnitProperties(unit string) (map[string]interface{}, error) {
-	return c.getProperties(unit, "org.freedesktop.systemd1.Unit")
+	path := unitPath(unit)
+	return c.getProperties(path, "org.freedesktop.systemd1.Unit")
+}
+
+// GetUnitProperties takes the (escaped) unit path and returns all of its dbus object properties.
+func (c *Conn) GetUnitPathProperties(path dbus.ObjectPath) (map[string]interface{}, error) {
+	return c.getProperties(path, "org.freedesktop.systemd1.Unit")
 }
 
 func (c *Conn) getProperty(unit string, dbusInterface string, propertyName string) (*Property, error) {
@@ -208,7 +228,8 @@ func (c *Conn) GetServiceProperty(service string, propertyName string) (*Propert
 // Valid values for unitType: Service, Socket, Target, Device, Mount, Automount, Snapshot, Timer, Swap, Path, Slice, Scope
 // return "dbus.Error: Unknown interface" if the unitType is not the correct type of the unit
 func (c *Conn) GetUnitTypeProperties(unit string, unitType string) (map[string]interface{}, error) {
-	return c.getProperties(unit, "org.freedesktop.systemd1."+unitType)
+	path := unitPath(unit)
+	return c.getProperties(path, "org.freedesktop.systemd1."+unitType)
 }
 
 // SetUnitProperties() may be used to modify certain unit properties at runtime.
@@ -563,3 +584,8 @@ func (c *Conn) Reload() error {
 func unitPath(name string) dbus.ObjectPath {
 	return dbus.ObjectPath("/org/freedesktop/systemd1/unit/" + PathBusEscape(name))
 }
+
+// unitName returns the unescaped base element of the supplied escaped path
+func unitName(dpath dbus.ObjectPath) string {
+	return pathBusUnescape(path.Base(string(dpath)))
+}

vendor/github.com/coreos/go-systemd/dbus/subscription.go

@@ -16,6 +16,7 @@ package dbus
 
 import (
 	"errors"
+	"log"
 	"time"
 
 	"github.com/godbus/dbus"
@@ -70,7 +71,8 @@ func (c *Conn) dispatch() {
 				c.jobComplete(signal)
 			}
 
-			if c.subscriber.updateCh == nil {
+			if c.subStateSubscriber.updateCh == nil &&
+				c.propertiesSubscriber.updateCh == nil {
 				continue
 			}
 
@@ -84,6 +86,12 @@ func (c *Conn) dispatch() {
 			case "org.freedesktop.DBus.Properties.PropertiesChanged":
 				if signal.Body[0].(string) == "org.freedesktop.systemd1.Unit" {
 					unitPath = signal.Path
+
+					if len(signal.Body) >= 2 {
+						if changed, ok := signal.Body[1].(map[string]dbus.Variant); ok {
+							c.sendPropertiesUpdate(unitPath, changed)
+						}
+					}
 				}
 			}
 
@@ -169,42 +177,80 @@ type SubStateUpdate struct {
 // is full, it attempts to write an error to errCh; if errCh is full, the error
 // passes silently.
 func (c *Conn) SetSubStateSubscriber(updateCh chan<- *SubStateUpdate, errCh chan<- error) {
-	c.subscriber.Lock()
-	defer c.subscriber.Unlock()
-	c.subscriber.updateCh = updateCh
-	c.subscriber.errCh = errCh
-}
-
-func (c *Conn) sendSubStateUpdate(path dbus.ObjectPath) {
-	c.subscriber.Lock()
-	defer c.subscriber.Unlock()
-
-	if c.shouldIgnore(path) {
+	if c == nil {
+		msg := "nil receiver"
+		select {
+		case errCh <- errors.New(msg):
+		default:
+			log.Printf("full error channel while reporting: %s\n", msg)
+		}
 		return
 	}
 
-	info, err := c.GetUnitProperties(string(path))
-	if err != nil {
-		select {
-		case c.subscriber.errCh <- err:
-		default:
-		}
+	c.subStateSubscriber.Lock()
+	defer c.subStateSubscriber.Unlock()
+	c.subStateSubscriber.updateCh = updateCh
+	c.subStateSubscriber.errCh = errCh
+}
+
+func (c *Conn) sendSubStateUpdate(unitPath dbus.ObjectPath) {
+	c.subStateSubscriber.Lock()
+	defer c.subStateSubscriber.Unlock()
+
+	if c.subStateSubscriber.updateCh == nil {
+		return
 	}
 
-	name := info["Id"].(string)
-	substate := info["SubState"].(string)
+	isIgnored := c.shouldIgnore(unitPath)
+	defer c.cleanIgnore()
+	if isIgnored {
+		return
+	}
+
+	info, err := c.GetUnitPathProperties(unitPath)
+	if err != nil {
+		select {
+		case c.subStateSubscriber.errCh <- err:
+		default:
+			log.Printf("full error channel while reporting: %s\n", err)
+		}
+		return
+	}
+	defer c.updateIgnore(unitPath, info)
+
+	name, ok := info["Id"].(string)
+	if !ok {
+		msg := "failed to cast info.Id"
+		select {
+		case c.subStateSubscriber.errCh <- errors.New(msg):
+		default:
+			log.Printf("full error channel while reporting: %s\n", err)
+		}
+		return
+	}
+	substate, ok := info["SubState"].(string)
+	if !ok {
+		msg := "failed to cast info.SubState"
+		select {
+		case c.subStateSubscriber.errCh <- errors.New(msg):
+		default:
+			log.Printf("full error channel while reporting: %s\n", msg)
+		}
+		return
+	}
 
 	update := &SubStateUpdate{name, substate}
 	select {
-	case c.subscriber.updateCh <- update:
+	case c.subStateSubscriber.updateCh <- update:
 	default:
+		msg := "update channel is full"
 		select {
-		case c.subscriber.errCh <- errors.New("update channel full!"):
+		case c.subStateSubscriber.errCh <- errors.New(msg):
 		default:
+			log.Printf("full error channel while reporting: %s\n", msg)
 		}
+		return
 	}
-
-	c.updateIgnore(path, info)
 }
 
 // The ignore functions work around a wart in the systemd dbus interface.
@@ -222,29 +268,76 @@ func (c *Conn) sendSubStateUpdate(path dbus.ObjectPath) {
 // the properties).
 
 func (c *Conn) shouldIgnore(path dbus.ObjectPath) bool {
-	t, ok := c.subscriber.ignore[path]
+	t, ok := c.subStateSubscriber.ignore[path]
 	return ok && t >= time.Now().UnixNano()
 }
 
 func (c *Conn) updateIgnore(path dbus.ObjectPath, info map[string]interface{}) {
-	c.cleanIgnore()
+	loadState, ok := info["LoadState"].(string)
+	if !ok {
+		return
+	}
 
 	// unit is unloaded - it will trigger bad systemd dbus behavior
-	if info["LoadState"].(string) == "not-found" {
-		c.subscriber.ignore[path] = time.Now().UnixNano() + ignoreInterval
+	if loadState == "not-found" {
+		c.subStateSubscriber.ignore[path] = time.Now().UnixNano() + ignoreInterval
 	}
 }
 
 // without this, ignore would grow unboundedly over time
 func (c *Conn) cleanIgnore() {
 	now := time.Now().UnixNano()
-	if c.subscriber.cleanIgnore < now {
-		c.subscriber.cleanIgnore = now + cleanIgnoreInterval
+	if c.subStateSubscriber.cleanIgnore < now {
+		c.subStateSubscriber.cleanIgnore = now + cleanIgnoreInterval
 
-		for p, t := range c.subscriber.ignore {
+		for p, t := range c.subStateSubscriber.ignore {
 			if t < now {
-				delete(c.subscriber.ignore, p)
+				delete(c.subStateSubscriber.ignore, p)
 			}
 		}
 	}
 }
+
+// PropertiesUpdate holds a map of a unit's changed properties
+type PropertiesUpdate struct {
+	UnitName string
+	Changed  map[string]dbus.Variant
+}
+
+// SetPropertiesSubscriber writes to updateCh when any unit's properties
+// change. Every property change reported by systemd will be sent; that is, no
+// transitions will be "missed" (as they might be with SetSubStateSubscriber).
+// However, state changes will only be written to the channel with non-blocking
+// writes.  If updateCh is full, it attempts to write an error to errCh; if
+// errCh is full, the error passes silently.
+func (c *Conn) SetPropertiesSubscriber(updateCh chan<- *PropertiesUpdate, errCh chan<- error) {
+	c.propertiesSubscriber.Lock()
+	defer c.propertiesSubscriber.Unlock()
+	c.propertiesSubscriber.updateCh = updateCh
+	c.propertiesSubscriber.errCh = errCh
+}
+
+// we don't need to worry about shouldIgnore() here because
+// sendPropertiesUpdate doesn't call GetProperties()
+func (c *Conn) sendPropertiesUpdate(unitPath dbus.ObjectPath, changedProps map[string]dbus.Variant) {
+	c.propertiesSubscriber.Lock()
+	defer c.propertiesSubscriber.Unlock()
+
+	if c.propertiesSubscriber.updateCh == nil {
+		return
+	}
+
+	update := &PropertiesUpdate{unitName(unitPath), changedProps}
+
+	select {
+	case c.propertiesSubscriber.updateCh <- update:
+	default:
+		msg := "update channel is full"
+		select {
+		case c.propertiesSubscriber.errCh <- errors.New(msg):
+		default:
+			log.Printf("full error channel while reporting: %s\n", msg)
+		}
+		return
+	}
+}

vendor/github.com/golang/protobuf/proto/discard.go

@@ -0,0 +1,151 @@
+// Go support for Protocol Buffers - Google's data interchange format
+//
+// Copyright 2017 The Go Authors.  All rights reserved.
+// https://github.com/golang/protobuf
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package proto
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// DiscardUnknown recursively discards all unknown fields from this message
+// and all embedded messages.
+//
+// When unmarshaling a message with unrecognized fields, the tags and values
+// of such fields are preserved in the Message. This allows a later call to
+// marshal to be able to produce a message that continues to have those
+// unrecognized fields. To avoid this, DiscardUnknown is used to
+// explicitly clear the unknown fields after unmarshaling.
+//
+// For proto2 messages, the unknown fields of message extensions are only
+// discarded from messages that have been accessed via GetExtension.
+func DiscardUnknown(m Message) {
+	discardLegacy(m)
+}
+
+func discardLegacy(m Message) {
+	v := reflect.ValueOf(m)
+	if v.Kind() != reflect.Ptr || v.IsNil() {
+		return
+	}
+	v = v.Elem()
+	if v.Kind() != reflect.Struct {
+		return
+	}
+	t := v.Type()
+
+	for i := 0; i < v.NumField(); i++ {
+		f := t.Field(i)
+		if strings.HasPrefix(f.Name, "XXX_") {
+			continue
+		}
+		vf := v.Field(i)
+		tf := f.Type
+
+		// Unwrap tf to get its most basic type.
+		var isPointer, isSlice bool
+		if tf.Kind() == reflect.Slice && tf.Elem().Kind() != reflect.Uint8 {
+			isSlice = true
+			tf = tf.Elem()
+		}
+		if tf.Kind() == reflect.Ptr {
+			isPointer = true
+			tf = tf.Elem()
+		}
+		if isPointer && isSlice && tf.Kind() != reflect.Struct {
+			panic(fmt.Sprintf("%T.%s cannot be a slice of pointers to primitive types", m, f.Name))
+		}
+
+		switch tf.Kind() {
+		case reflect.Struct:
+			switch {
+			case !isPointer:
+				panic(fmt.Sprintf("%T.%s cannot be a direct struct value", m, f.Name))
+			case isSlice: // E.g., []*pb.T
+				for j := 0; j < vf.Len(); j++ {
+					discardLegacy(vf.Index(j).Interface().(Message))
+				}
+			default: // E.g., *pb.T
+				discardLegacy(vf.Interface().(Message))
+			}
+		case reflect.Map:
+			switch {
+			case isPointer || isSlice:
+				panic(fmt.Sprintf("%T.%s cannot be a pointer to a map or a slice of map values", m, f.Name))
+			default: // E.g., map[K]V
+				tv := vf.Type().Elem()
+				if tv.Kind() == reflect.Ptr && tv.Implements(protoMessageType) { // Proto struct (e.g., *T)
+					for _, key := range vf.MapKeys() {
+						val := vf.MapIndex(key)
+						discardLegacy(val.Interface().(Message))
+					}
+				}
+			}
+		case reflect.Interface:
+			// Must be oneof field.
+			switch {
+			case isPointer || isSlice:
+				panic(fmt.Sprintf("%T.%s cannot be a pointer to a interface or a slice of interface values", m, f.Name))
+			default: // E.g., test_proto.isCommunique_Union interface
+				if !vf.IsNil() && f.Tag.Get("protobuf_oneof") != "" {
+					vf = vf.Elem() // E.g., *test_proto.Communique_Msg
+					if !vf.IsNil() {
+						vf = vf.Elem()   // E.g., test_proto.Communique_Msg
+						vf = vf.Field(0) // E.g., Proto struct (e.g., *T) or primitive value
+						if vf.Kind() == reflect.Ptr {
+							discardLegacy(vf.Interface().(Message))
+						}
+					}
+				}
+			}
+		}
+	}
+
+	if vf := v.FieldByName("XXX_unrecognized"); vf.IsValid() {
+		if vf.Type() != reflect.TypeOf([]byte{}) {
+			panic("expected XXX_unrecognized to be of type []byte")
+		}
+		vf.Set(reflect.ValueOf([]byte(nil)))
+	}
+
+	// For proto2 messages, only discard unknown fields in message extensions
+	// that have been accessed via GetExtension.
+	if em, ok := extendable(m); ok {
+		// Ignore lock since discardLegacy is not concurrency safe.
+		emm, _ := em.extensionsRead()
+		for _, mx := range emm {
+			if m, ok := mx.value.(Message); ok {
+				discardLegacy(m)
+			}
+		}
+	}
+}

vendor/github.com/prometheus/client_golang/prometheus/doc.go

@@ -11,10 +11,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package prometheus provides metrics primitives to instrument code for
-// monitoring. It also offers a registry for metrics. Sub-packages allow to
-// expose the registered metrics via HTTP (package promhttp) or push them to a
-// Pushgateway (package push).
+// Package prometheus is the core instrumentation package. It provides metrics
+// primitives to instrument code for monitoring. It also offers a registry for
+// metrics. Sub-packages allow to expose the registered metrics via HTTP
+// (package promhttp) or push them to a Pushgateway (package push). There is
+// also a sub-package promauto, which provides metrics constructors with
+// automatic registration.
 //
 // All exported functions and methods are safe to be used concurrently unless
 // specified otherwise.
@@ -72,7 +74,10 @@
 // The number of exported identifiers in this package might appear a bit
 // overwhelming. However, in addition to the basic plumbing shown in the example
 // above, you only need to understand the different metric types and their
-// vector versions for basic usage.
+// vector versions for basic usage. Furthermore, if you are not concerned with
+// fine-grained control of when and how to register metrics with the registry,
+// have a look at the promauto package, which will effectively allow you to
+// ignore registration altogether in simple cases.
 //
 // Above, you have already touched the Counter and the Gauge. There are two more
 // advanced metric types: the Summary and Histogram. A more thorough description

vendor/github.com/prometheus/client_golang/prometheus/http.go

@@ -61,9 +61,8 @@ func giveBuf(buf *bytes.Buffer) {
 // name).
 //
 // Deprecated: Please note the issues described in the doc comment of
-// InstrumentHandler. You might want to consider using promhttp.Handler instead
-// (which is not instrumented, but can be instrumented with the tooling provided
-// in package promhttp).
+// InstrumentHandler. You might want to consider using
+// promhttp.InstrumentedHandler instead.
 func Handler() http.Handler {
 	return InstrumentHandler("prometheus", UninstrumentedHandler())
 }

vendor/github.com/prometheus/client_golang/prometheus/process_collector.go

@@ -26,8 +26,11 @@ type processCollector struct {
 }
 
 // NewProcessCollector returns a collector which exports the current state of
-// process metrics including cpu, memory and file descriptor usage as well as
-// the process start time for the given process id under the given namespace.
+// process metrics including CPU, memory and file descriptor usage as well as
+// the process start time for the given process ID under the given namespace.
+//
+// Currently, the collector depends on a Linux-style proc filesystem and
+// therefore only exports metrics for Linux.
 func NewProcessCollector(pid int, namespace string) Collector {
 	return NewProcessCollectorPIDFn(
 		func() (int, error) { return pid, nil },
@@ -35,11 +38,8 @@ func NewProcessCollector(pid int, namespace string) Collector {
 	)
 }
 
-// NewProcessCollectorPIDFn returns a collector which exports the current state
-// of process metrics including cpu, memory and file descriptor usage as well
-// as the process start time under the given namespace. The given pidFn is
-// called on each collect and is used to determine the process to export
-// metrics for.
+// NewProcessCollectorPIDFn works like NewProcessCollector but the process ID is
+// determined on each collect anew by calling the given pidFn function.
 func NewProcessCollectorPIDFn(
 	pidFn func() (int, error),
 	namespace string,

vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator.go

@@ -102,10 +102,10 @@ func init() {
 		return d
 	}
 	pickDelegator[closeNotifier] = func(d *responseWriterDelegator) delegator { // 1
-		return closeNotifierDelegator{d}
+		return &closeNotifierDelegator{d}
 	}
 	pickDelegator[flusher] = func(d *responseWriterDelegator) delegator { // 2
-		return flusherDelegator{d}
+		return &flusherDelegator{d}
 	}
 	pickDelegator[flusher+closeNotifier] = func(d *responseWriterDelegator) delegator { // 3
 		return struct {
@@ -115,7 +115,7 @@ func init() {
 		}{d, &flusherDelegator{d}, &closeNotifierDelegator{d}}
 	}
 	pickDelegator[hijacker] = func(d *responseWriterDelegator) delegator { // 4
-		return hijackerDelegator{d}
+		return &hijackerDelegator{d}
 	}
 	pickDelegator[hijacker+closeNotifier] = func(d *responseWriterDelegator) delegator { // 5
 		return struct {

vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator_1_8.go

@@ -28,7 +28,7 @@ func (d *pusherDelegator) Push(target string, opts *http.PushOptions) error {
 
 func init() {
 	pickDelegator[pusher] = func(d *responseWriterDelegator) delegator { // 16
-		return pusherDelegator{d}
+		return &pusherDelegator{d}
 	}
 	pickDelegator[pusher+closeNotifier] = func(d *responseWriterDelegator) delegator { // 17
 		return struct {

vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go

@@ -39,6 +39,7 @@ import (
 	"net/http"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/prometheus/common/expfmt"
 
@@ -67,21 +68,51 @@ func giveBuf(buf *bytes.Buffer) {
 	bufPool.Put(buf)
 }
 
-// Handler returns an HTTP handler for the prometheus.DefaultGatherer. The
-// Handler uses the default HandlerOpts, i.e. report the first error as an HTTP
-// error, no error logging, and compression if requested by the client.
+// Handler returns an http.Handler for the prometheus.DefaultGatherer, using
+// default HandlerOpts, i.e. it reports the first error as an HTTP error, it has
+// no error logging, and it applies compression if requested by the client.
 //
-// If you want to create a Handler for the DefaultGatherer with different
-// HandlerOpts, create it with HandlerFor with prometheus.DefaultGatherer and
-// your desired HandlerOpts.
+// The returned http.Handler is already instrumented using the
+// InstrumentMetricHandler function and the prometheus.DefaultRegisterer. If you
+// create multiple http.Handlers by separate calls of the Handler function, the
+// metrics used for instrumentation will be shared between them, providing
+// global scrape counts.
+//
+// This function is meant to cover the bulk of basic use cases. If you are doing
+// anything that requires more customization (including using a non-default
+// Gatherer, different instrumentation, and non-default HandlerOpts), use the
+// HandlerFor function. See there for details.
 func Handler() http.Handler {
-	return HandlerFor(prometheus.DefaultGatherer, HandlerOpts{})
+	return InstrumentMetricHandler(
+		prometheus.DefaultRegisterer, HandlerFor(prometheus.DefaultGatherer, HandlerOpts{}),
+	)
 }
 
-// HandlerFor returns an http.Handler for the provided Gatherer. The behavior
-// of the Handler is defined by the provided HandlerOpts.
+// HandlerFor returns an uninstrumented http.Handler for the provided
+// Gatherer. The behavior of the Handler is defined by the provided
+// HandlerOpts. Thus, HandlerFor is useful to create http.Handlers for custom
+// Gatherers, with non-default HandlerOpts, and/or with custom (or no)
+// instrumentation. Use the InstrumentMetricHandler function to apply the same
+// kind of instrumentation as it is used by the Handler function.
 func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+	var inFlightSem chan struct{}
+	if opts.MaxRequestsInFlight > 0 {
+		inFlightSem = make(chan struct{}, opts.MaxRequestsInFlight)
+	}
+
+	h := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		if inFlightSem != nil {
+			select {
+			case inFlightSem <- struct{}{}: // All good, carry on.
+				defer func() { <-inFlightSem }()
+			default:
+				http.Error(w, fmt.Sprintf(
+					"Limit of concurrent requests reached (%d), try again later.", opts.MaxRequestsInFlight,
+				), http.StatusServiceUnavailable)
+				return
+			}
+		}
+
 		mfs, err := reg.Gather()
 		if err != nil {
 			if opts.ErrorLog != nil {
@@ -137,9 +168,70 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
 		if encoding != "" {
 			header.Set(contentEncodingHeader, encoding)
 		}
-		w.Write(buf.Bytes())
+		if _, err := w.Write(buf.Bytes()); err != nil && opts.ErrorLog != nil {
+			opts.ErrorLog.Println("error while sending encoded metrics:", err)
+		}
 		// TODO(beorn7): Consider streaming serving of metrics.
 	})
+
+	if opts.Timeout <= 0 {
+		return h
+	}
+	return http.TimeoutHandler(h, opts.Timeout, fmt.Sprintf(
+		"Exceeded configured timeout of %v.\n",
+		opts.Timeout,
+	))
+}
+
+// InstrumentMetricHandler is usually used with an http.Handler returned by the
+// HandlerFor function. It instruments the provided http.Handler with two
+// metrics: A counter vector "promhttp_metric_handler_requests_total" to count
+// scrapes partitioned by HTTP status code, and a gauge
+// "promhttp_metric_handler_requests_in_flight" to track the number of
+// simultaneous scrapes. This function idempotently registers collectors for
+// both metrics with the provided Registerer. It panics if the registration
+// fails. The provided metrics are useful to see how many scrapes hit the
+// monitored target (which could be from different Prometheus servers or other
+// scrapers), and how often they overlap (which would result in more than one
+// scrape in flight at the same time). Note that the scrapes-in-flight gauge
+// will contain the scrape by which it is exposed, while the scrape counter will
+// only get incremented after the scrape is complete (as only then the status
+// code is known). For tracking scrape durations, use the
+// "scrape_duration_seconds" gauge created by the Prometheus server upon each
+// scrape.
+func InstrumentMetricHandler(reg prometheus.Registerer, handler http.Handler) http.Handler {
+	cnt := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "promhttp_metric_handler_requests_total",
+			Help: "Total number of scrapes by HTTP status code.",
+		},
+		[]string{"code"},
+	)
+	// Initialize the most likely HTTP status codes.
+	cnt.WithLabelValues("200")
+	cnt.WithLabelValues("500")
+	cnt.WithLabelValues("503")
+	if err := reg.Register(cnt); err != nil {
+		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+			cnt = are.ExistingCollector.(*prometheus.CounterVec)
+		} else {
+			panic(err)
+		}
+	}
+
+	gge := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "promhttp_metric_handler_requests_in_flight",
+		Help: "Current number of scrapes being served.",
+	})
+	if err := reg.Register(gge); err != nil {
+		if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
+			gge = are.ExistingCollector.(prometheus.Gauge)
+		} else {
+			panic(err)
+		}
+	}
+
+	return InstrumentHandlerCounter(cnt, InstrumentHandlerInFlight(gge, handler))
 }
 
 // HandlerErrorHandling defines how a Handler serving metrics will handle
@@ -183,6 +275,21 @@ type HandlerOpts struct {
 	// If DisableCompression is true, the handler will never compress the
 	// response, even if requested by the client.
 	DisableCompression bool
+	// The number of concurrent HTTP requests is limited to
+	// MaxRequestsInFlight. Additional requests are responded to with 503
+	// Service Unavailable and a suitable message in the body. If
+	// MaxRequestsInFlight is 0 or negative, no limit is applied.
+	MaxRequestsInFlight int
+	// If handling a request takes longer than Timeout, it is responded to
+	// with 503 ServiceUnavailable and a suitable Message. No timeout is
+	// applied if Timeout is 0 or negative. Note that with the current
+	// implementation, reaching the timeout simply ends the HTTP requests as
+	// described above (and even that only if sending of the body hasn't
+	// started yet), while the bulk work of gathering all the metrics keeps
+	// running in the background (with the eventual result to be thrown
+	// away). Until the implementation is improved, it is recommended to
+	// implement a separate timeout in potentially slow Collectors.
+	Timeout time.Duration
 }
 
 // decorateWriter wraps a writer to handle gzip compression if requested.  It

vendor/github.com/prometheus/client_golang/prometheus/registry.go

@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"runtime"
 	"sort"
 	"sync"
 	"unicode/utf8"
@@ -36,13 +37,13 @@ const (
 // DefaultRegisterer and DefaultGatherer are the implementations of the
 // Registerer and Gatherer interface a number of convenience functions in this
 // package act on. Initially, both variables point to the same Registry, which
-// has a process collector (see NewProcessCollector) and a Go collector (see
-// NewGoCollector) already registered. This approach to keep default instances
-// as global state mirrors the approach of other packages in the Go standard
-// library. Note that there are caveats. Change the variables with caution and
-// only if you understand the consequences. Users who want to avoid global state
-// altogether should not use the convenience function and act on custom
-// instances instead.
+// has a process collector (currently on Linux only, see NewProcessCollector)
+// and a Go collector (see NewGoCollector) already registered. This approach to
+// keep default instances as global state mirrors the approach of other packages
+// in the Go standard library. Note that there are caveats. Change the variables
+// with caution and only if you understand the consequences. Users who want to
+// avoid global state altogether should not use the convenience functions and
+// act on custom instances instead.
 var (
 	defaultRegistry              = NewRegistry()
 	DefaultRegisterer Registerer = defaultRegistry
@@ -202,6 +203,13 @@ func (errs MultiError) Error() string {
 	return buf.String()
 }
 
+// Append appends the provided error if it is not nil.
+func (errs *MultiError) Append(err error) {
+	if err != nil {
+		*errs = append(*errs, err)
+	}
+}
+
 // MaybeUnwrap returns nil if len(errs) is 0. It returns the first and only
 // contained error as error if len(errs is 1). In all other cases, it returns
 // the MultiError directly. This is helpful for returning a MultiError in a way
@@ -368,22 +376,12 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 	)
 
 	r.mtx.RLock()
+	goroutineBudget := len(r.collectorsByID)
 	metricFamiliesByName := make(map[string]*dto.MetricFamily, len(r.dimHashesByName))
-
-	// Scatter.
-	// (Collectors could be complex and slow, so we call them all at once.)
-	wg.Add(len(r.collectorsByID))
-	go func() {
-		wg.Wait()
-		close(metricChan)
-	}()
+	collectors := make(chan Collector, len(r.collectorsByID))
 	for _, collector := range r.collectorsByID {
-		go func(collector Collector) {
-			defer wg.Done()
-			collector.Collect(metricChan)
-		}(collector)
+		collectors <- collector
 	}
-
 	// In case pedantic checks are enabled, we have to copy the map before
 	// giving up the RLock.
 	if r.pedanticChecksEnabled {
@@ -392,129 +390,176 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 			registeredDescIDs[id] = struct{}{}
 		}
 	}
-
 	r.mtx.RUnlock()
 
+	wg.Add(goroutineBudget)
+
+	collectWorker := func() {
+		for {
+			select {
+			case collector := <-collectors:
+				collector.Collect(metricChan)
+				wg.Done()
+			default:
+				return
+			}
+		}
+	}
+
+	// Start the first worker now to make sure at least one is running.
+	go collectWorker()
+	goroutineBudget--
+
+	// Close the metricChan once all collectors are collected.
+	go func() {
+		wg.Wait()
+		close(metricChan)
+	}()
+
 	// Drain metricChan in case of premature return.
 	defer func() {
 		for range metricChan {
 		}
 	}()
 
-	// Gather.
-	for metric := range metricChan {
-		// This could be done concurrently, too, but it required locking
-		// of metricFamiliesByName (and of metricHashes if checks are
-		// enabled). Most likely not worth it.
-		desc := metric.Desc()
-		dtoMetric := &dto.Metric{}
-		if err := metric.Write(dtoMetric); err != nil {
-			errs = append(errs, fmt.Errorf(
-				"error collecting metric %v: %s", desc, err,
+collectLoop:
+	for {
+		select {
+		case metric, ok := <-metricChan:
+			if !ok {
+				// metricChan is closed, we are done.
+				break collectLoop
+			}
+			errs.Append(processMetric(
+				metric, metricFamiliesByName,
+				metricHashes, dimHashes,
+				registeredDescIDs,
 			))
-			continue
+		default:
+			if goroutineBudget <= 0 || len(collectors) == 0 {
+				// All collectors are aleady being worked on or
+				// we have already as many goroutines started as
+				// there are collectors. Just process metrics
+				// from now on.
+				for metric := range metricChan {
+					errs.Append(processMetric(
+						metric, metricFamiliesByName,
+						metricHashes, dimHashes,
+						registeredDescIDs,
+					))
+				}
+				break collectLoop
+			}
+			// Start more workers.
+			go collectWorker()
+			goroutineBudget--
+			runtime.Gosched()
 		}
-		metricFamily, ok := metricFamiliesByName[desc.fqName]
-		if ok {
-			if metricFamily.GetHelp() != desc.help {
-				errs = append(errs, fmt.Errorf(
-					"collected metric %s %s has help %q but should have %q",
-					desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
-				))
-				continue
-			}
-			// TODO(beorn7): Simplify switch once Desc has type.
-			switch metricFamily.GetType() {
-			case dto.MetricType_COUNTER:
-				if dtoMetric.Counter == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Counter",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_GAUGE:
-				if dtoMetric.Gauge == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Gauge",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_SUMMARY:
-				if dtoMetric.Summary == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Summary",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_UNTYPED:
-				if dtoMetric.Untyped == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be Untyped",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			case dto.MetricType_HISTOGRAM:
-				if dtoMetric.Histogram == nil {
-					errs = append(errs, fmt.Errorf(
-						"collected metric %s %s should be a Histogram",
-						desc.fqName, dtoMetric,
-					))
-					continue
-				}
-			default:
-				panic("encountered MetricFamily with invalid type")
-			}
-		} else {
-			metricFamily = &dto.MetricFamily{}
-			metricFamily.Name = proto.String(desc.fqName)
-			metricFamily.Help = proto.String(desc.help)
-			// TODO(beorn7): Simplify switch once Desc has type.
-			switch {
-			case dtoMetric.Gauge != nil:
-				metricFamily.Type = dto.MetricType_GAUGE.Enum()
-			case dtoMetric.Counter != nil:
-				metricFamily.Type = dto.MetricType_COUNTER.Enum()
-			case dtoMetric.Summary != nil:
-				metricFamily.Type = dto.MetricType_SUMMARY.Enum()
-			case dtoMetric.Untyped != nil:
-				metricFamily.Type = dto.MetricType_UNTYPED.Enum()
-			case dtoMetric.Histogram != nil:
-				metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
-			default:
-				errs = append(errs, fmt.Errorf(
-					"empty metric collected: %s", dtoMetric,
-				))
-				continue
-			}
-			metricFamiliesByName[desc.fqName] = metricFamily
-		}
-		if err := checkMetricConsistency(metricFamily, dtoMetric, metricHashes, dimHashes); err != nil {
-			errs = append(errs, err)
-			continue
-		}
-		if r.pedanticChecksEnabled {
-			// Is the desc registered at all?
-			if _, exist := registeredDescIDs[desc.id]; !exist {
-				errs = append(errs, fmt.Errorf(
-					"collected metric %s %s with unregistered descriptor %s",
-					metricFamily.GetName(), dtoMetric, desc,
-				))
-				continue
-			}
-			if err := checkDescConsistency(metricFamily, dtoMetric, desc); err != nil {
-				errs = append(errs, err)
-				continue
-			}
-		}
-		metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
 	}
 	return normalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
 }
 
+// processMetric is an internal helper method only used by the Gather method.
+func processMetric(
+	metric Metric,
+	metricFamiliesByName map[string]*dto.MetricFamily,
+	metricHashes map[uint64]struct{},
+	dimHashes map[string]uint64,
+	registeredDescIDs map[uint64]struct{},
+) error {
+	desc := metric.Desc()
+	dtoMetric := &dto.Metric{}
+	if err := metric.Write(dtoMetric); err != nil {
+		return fmt.Errorf("error collecting metric %v: %s", desc, err)
+	}
+	metricFamily, ok := metricFamiliesByName[desc.fqName]
+	if ok {
+		if metricFamily.GetHelp() != desc.help {
+			return fmt.Errorf(
+				"collected metric %s %s has help %q but should have %q",
+				desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
+			)
+		}
+		// TODO(beorn7): Simplify switch once Desc has type.
+		switch metricFamily.GetType() {
+		case dto.MetricType_COUNTER:
+			if dtoMetric.Counter == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Counter",
+					desc.fqName, dtoMetric,
+				)
+			}
+		case dto.MetricType_GAUGE:
+			if dtoMetric.Gauge == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Gauge",
+					desc.fqName, dtoMetric,
+				)
+			}
+		case dto.MetricType_SUMMARY:
+			if dtoMetric.Summary == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Summary",
+					desc.fqName, dtoMetric,
+				)
+			}
+		case dto.MetricType_UNTYPED:
+			if dtoMetric.Untyped == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be Untyped",
+					desc.fqName, dtoMetric,
+				)
+			}
+		case dto.MetricType_HISTOGRAM:
+			if dtoMetric.Histogram == nil {
+				return fmt.Errorf(
+					"collected metric %s %s should be a Histogram",
+					desc.fqName, dtoMetric,
+				)
+			}
+		default:
+			panic("encountered MetricFamily with invalid type")
+		}
+	} else {
+		metricFamily = &dto.MetricFamily{}
+		metricFamily.Name = proto.String(desc.fqName)
+		metricFamily.Help = proto.String(desc.help)
+		// TODO(beorn7): Simplify switch once Desc has type.
+		switch {
+		case dtoMetric.Gauge != nil:
+			metricFamily.Type = dto.MetricType_GAUGE.Enum()
+		case dtoMetric.Counter != nil:
+			metricFamily.Type = dto.MetricType_COUNTER.Enum()
+		case dtoMetric.Summary != nil:
+			metricFamily.Type = dto.MetricType_SUMMARY.Enum()
+		case dtoMetric.Untyped != nil:
+			metricFamily.Type = dto.MetricType_UNTYPED.Enum()
+		case dtoMetric.Histogram != nil:
+			metricFamily.Type = dto.MetricType_HISTOGRAM.Enum()
+		default:
+			return fmt.Errorf("empty metric collected: %s", dtoMetric)
+		}
+		metricFamiliesByName[desc.fqName] = metricFamily
+	}
+	if err := checkMetricConsistency(metricFamily, dtoMetric, metricHashes, dimHashes); err != nil {
+		return err
+	}
+	if registeredDescIDs != nil {
+		// Is the desc registered at all?
+		if _, exist := registeredDescIDs[desc.id]; !exist {
+			return fmt.Errorf(
+				"collected metric %s %s with unregistered descriptor %s",
+				metricFamily.GetName(), dtoMetric, desc,
+			)
+		}
+		if err := checkDescConsistency(metricFamily, dtoMetric, desc); err != nil {
+			return err
+		}
+	}
+	metricFamily.Metric = append(metricFamily.Metric, dtoMetric)
+	return nil
+}
+
 // Gatherers is a slice of Gatherer instances that implements the Gatherer
 // interface itself. Its Gather method calls Gather on all Gatherers in the
 // slice in order and returns the merged results. Errors returned from the