Merge branch 'bjk/159_metics_names' into 'master'

Update metrics

See merge request gitlab-org/gitlab-pages!103

16 files changed, 397 insertions, 175 deletions

diff --git a/acceptance_test.go b/acceptance_test.go
index 28ebdeb8..8023c4ff 100644
--- a/acceptance_test.go
+++ b/acceptance_test.go
@@ -393,8 +393,8 @@ func TestPrometheusMetricsCanBeScraped(t *testing.T) {
 		defer resp.Body.Close()
 		body, _ := ioutil.ReadAll(resp.Body)
 
-		assert.Contains(t, string(body), "gitlab_pages_http_sessions_active 0")
-		assert.Contains(t, string(body), "gitlab_pages_domains_served_total 16")
+		assert.Contains(t, string(body), "gitlab_pages_http_active_sessions 0")
+		assert.Contains(t, string(body), "gitlab_pages_served_domains 16")
 	}
 }
 
diff --git a/app.go b/app.go
index 2cb8bbd9..da1a5315 100644
--- a/app.go
+++ b/app.go
@@ -12,7 +12,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/rs/cors"
 	log "github.com/sirupsen/logrus"
@@ -301,7 +300,7 @@ func (a *theApp) Run() {
 		go func(fd uintptr) {
 			defer wg.Done()
 
-			handler := promhttp.HandlerFor(prometheus.DefaultGatherer, promhttp.HandlerOpts{}).ServeHTTP
+			handler := promhttp.Handler().ServeHTTP
 			err := listenAndServe(fd, handler, false, nil, nil)
 			if err != nil {
 				capturingFatal(err, errortracking.WithField("listener", "metrics"))
diff --git a/metrics/metrics.go b/metrics/metrics.go
index 44350ae5..3bf4d7a8 100644
--- a/metrics/metrics.go
+++ b/metrics/metrics.go
@@ -7,8 +7,8 @@ import (
 var (
 	// DomainsServed counts the total number of sites served
 	DomainsServed = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "gitlab_pages_domains_served_total",
-		Help: "The total number of sites served by this Pages app",
+		Name: "gitlab_pages_served_domains",
+		Help: "The number of sites served by this Pages app",
 	})
 
 	// FailedDomainUpdates counts the number of failed site updates
@@ -39,7 +39,7 @@ var (
 
 	// SessionsActive is the number of HTTP requests currently being processed
 	SessionsActive = prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "gitlab_pages_http_sessions_active",
+		Name: "gitlab_pages_http_active_sessions",
 		Help: "The number of HTTP requests currently being processed",
 	})
 )
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/collector.go b/vendor/github.com/prometheus/client_golang/prometheus/collector.go
index c0d70b2f..1e839650 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/collector.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/collector.go
@@ -79,7 +79,7 @@ type Collector interface {
 // of the Describe method. If a Collector sometimes collects no metrics at all
 // (for example vectors like CounterVec, GaugeVec, etc., which only collect
 // metrics after a metric with a fully specified label set has been accessed),
-// it might even get registered as an unchecked Collecter (cf. the Register
+// it might even get registered as an unchecked Collector (cf. the Register
 // method of the Registerer interface). Hence, only use this shortcut
 // implementation of Describe if you are certain to fulfill the contract.
 //
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/counter.go b/vendor/github.com/prometheus/client_golang/prometheus/counter.go
index 765e4550..d463e36d 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/counter.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/counter.go
@@ -136,7 +136,7 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 	return &CounterVec{
 		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
 			if len(lvs) != len(desc.variableLabels) {
-				panic(errInconsistentCardinality)
+				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
 			}
 			result := &counter{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
 			result.init(result) // Init self-collection.
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/desc.go b/vendor/github.com/prometheus/client_golang/prometheus/desc.go
index 7b8827ff..1d034f87 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/desc.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/desc.go
@@ -93,7 +93,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 	// First add only the const label names and sort them...
 	for labelName := range constLabels {
 		if !checkLabelName(labelName) {
-			d.err = fmt.Errorf("%q is not a valid label name", labelName)
+			d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName)
 			return d
 		}
 		labelNames = append(labelNames, labelName)
@@ -115,7 +115,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 	// dimension with a different mix between preset and variable labels.
 	for _, labelName := range variableLabels {
 		if !checkLabelName(labelName) {
-			d.err = fmt.Errorf("%q is not a valid label name", labelName)
+			d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName)
 			return d
 		}
 		labelNames = append(labelNames, "$"+labelName)
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/doc.go b/vendor/github.com/prometheus/client_golang/prometheus/doc.go
index 5d9525de..1e0d578e 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/doc.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/doc.go
@@ -122,13 +122,13 @@
 // the Collect method. The Describe method has to return separate Desc
 // instances, representative of the “throw-away” metrics to be created later.
 // NewDesc comes in handy to create those Desc instances. Alternatively, you
-// could return no Desc at all, which will marke the Collector “unchecked”.  No
-// checks are porformed at registration time, but metric consistency will still
+// could return no Desc at all, which will mark the Collector “unchecked”.  No
+// checks are performed at registration time, but metric consistency will still
 // be ensured at scrape time, i.e. any inconsistencies will lead to scrape
 // errors. Thus, with unchecked Collectors, the responsibility to not collect
 // metrics that lead to inconsistencies in the total scrape result lies with the
 // implementer of the Collector. While this is not a desirable state, it is
-// sometimes necessary. The typical use case is a situatios where the exact
+// sometimes necessary. The typical use case is a situation where the exact
 // metrics to be returned by a Collector cannot be predicted at registration
 // time, but the implementer has sufficient knowledge of the whole system to
 // guarantee metric consistency.
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/gauge.go b/vendor/github.com/prometheus/client_golang/prometheus/gauge.go
index 17c72d7e..71d406bd 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/gauge.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/gauge.go
@@ -147,7 +147,7 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
 	return &GaugeVec{
 		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
 			if len(lvs) != len(desc.variableLabels) {
-				panic(errInconsistentCardinality)
+				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
 			}
 			result := &gauge{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
 			result.init(result) // Init self-collection.
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go b/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go
index ba3b9333..b108ec51 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/go_collector.go
@@ -14,9 +14,9 @@
 package prometheus
 
 import (
-	"fmt"
 	"runtime"
 	"runtime/debug"
+	"sync"
 	"time"
 )
 
@@ -26,16 +26,41 @@ type goCollector struct {
 	gcDesc         *Desc
 	goInfoDesc     *Desc
 
-	// metrics to describe and collect
-	metrics memStatsMetrics
+	// ms... are memstats related.
+	msLast          *runtime.MemStats // Previously collected memstats.
+	msLastTimestamp time.Time
+	msMtx           sync.Mutex // Protects msLast and msLastTimestamp.
+	msMetrics       memStatsMetrics
+	msRead          func(*runtime.MemStats) // For mocking in tests.
+	msMaxWait       time.Duration           // Wait time for fresh memstats.
+	msMaxAge        time.Duration           // Maximum allowed age of old memstats.
 }
 
 // NewGoCollector returns a collector which exports metrics about the current Go
 // process. This includes memory stats. To collect those, runtime.ReadMemStats
-// is called. This causes a stop-the-world, which is very short with Go1.9+
-// (~25µs). However, with older Go versions, the stop-the-world duration depends
-// on the heap size and can be quite significant (~1.7 ms/GiB as per
+// is called. This requires to “stop the world”, which usually only happens for
+// garbage collection (GC). Take the following implications into account when
+// deciding whether to use the Go collector:
+//
+// 1. The performance impact of stopping the world is the more relevant the more
+// frequently metrics are collected. However, with Go1.9 or later the
+// stop-the-world time per metrics collection is very short (~25µs) so that the
+// performance impact will only matter in rare cases. However, with older Go
+// versions, the stop-the-world duration depends on the heap size and can be
+// quite significant (~1.7 ms/GiB as per
 // https://go-review.googlesource.com/c/go/+/34937).
+//
+// 2. During an ongoing GC, nothing else can stop the world. Therefore, if the
+// metrics collection happens to coincide with GC, it will only complete after
+// GC has finished. Usually, GC is fast enough to not cause problems. However,
+// with a very large heap, GC might take multiple seconds, which is enough to
+// cause scrape timeouts in common setups. To avoid this problem, the Go
+// collector will use the memstats from a previous collection if
+// runtime.ReadMemStats takes more than 1s. However, if there are no previously
+// collected memstats, or their collection is more than 5m ago, the collection
+// will block until runtime.ReadMemStats succeeds. (The problem might be solved
+// in Go1.13, see https://github.com/golang/go/issues/19812 for the related Go
+// issue.)
 func NewGoCollector() Collector {
 	return &goCollector{
 		goroutinesDesc: NewDesc(
@@ -54,7 +79,11 @@ func NewGoCollector() Collector {
 			"go_info",
 			"Information about the Go environment.",
 			nil, Labels{"version": runtime.Version()}),
-		metrics: memStatsMetrics{
+		msLast:    &runtime.MemStats{},
+		msRead:    runtime.ReadMemStats,
+		msMaxWait: time.Second,
+		msMaxAge:  5 * time.Minute,
+		msMetrics: memStatsMetrics{
 			{
 				desc: NewDesc(
 					memstatNamespace("alloc_bytes"),
@@ -253,7 +282,7 @@ func NewGoCollector() Collector {
 }
 
 func memstatNamespace(s string) string {
-	return fmt.Sprintf("go_memstats_%s", s)
+	return "go_memstats_" + s
 }
 
 // Describe returns all descriptions of the collector.
@@ -262,13 +291,27 @@ func (c *goCollector) Describe(ch chan<- *Desc) {
 	ch <- c.threadsDesc
 	ch <- c.gcDesc
 	ch <- c.goInfoDesc
-	for _, i := range c.metrics {
+	for _, i := range c.msMetrics {
 		ch <- i.desc
 	}
 }
 
 // Collect returns the current state of all metrics of the collector.
 func (c *goCollector) Collect(ch chan<- Metric) {
+	var (
+		ms   = &runtime.MemStats{}
+		done = make(chan struct{})
+	)
+	// Start reading memstats first as it might take a while.
+	go func() {
+		c.msRead(ms)
+		c.msMtx.Lock()
+		c.msLast = ms
+		c.msLastTimestamp = time.Now()
+		c.msMtx.Unlock()
+		close(done)
+	}()
+
 	ch <- MustNewConstMetric(c.goroutinesDesc, GaugeValue, float64(runtime.NumGoroutine()))
 	n, _ := runtime.ThreadCreateProfile(nil)
 	ch <- MustNewConstMetric(c.threadsDesc, GaugeValue, float64(n))
@@ -286,9 +329,31 @@ func (c *goCollector) Collect(ch chan<- Metric) {
 
 	ch <- MustNewConstMetric(c.goInfoDesc, GaugeValue, 1)
 
-	ms := &runtime.MemStats{}
-	runtime.ReadMemStats(ms)
-	for _, i := range c.metrics {
+	timer := time.NewTimer(c.msMaxWait)
+	select {
+	case <-done: // Our own ReadMemStats succeeded in time. Use it.
+		timer.Stop() // Important for high collection frequencies to not pile up timers.
+		c.msCollect(ch, ms)
+		return
+	case <-timer.C: // Time out, use last memstats if possible. Continue below.
+	}
+	c.msMtx.Lock()
+	if time.Since(c.msLastTimestamp) < c.msMaxAge {
+		// Last memstats are recent enough. Collect from them under the lock.
+		c.msCollect(ch, c.msLast)
+		c.msMtx.Unlock()
+		return
+	}
+	// If we are here, the last memstats are too old or don't exist. We have
+	// to wait until our own ReadMemStats finally completes. For that to
+	// happen, we have to release the lock.
+	c.msMtx.Unlock()
+	<-done
+	c.msCollect(ch, ms)
+}
+
+func (c *goCollector) msCollect(ch chan<- Metric, ms *runtime.MemStats) {
+	for _, i := range c.msMetrics {
 		ch <- MustNewConstMetric(i.desc, i.valType, i.eval(ms))
 	}
 }
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/histogram.go b/vendor/github.com/prometheus/client_golang/prometheus/histogram.go
index 4d7fa976..d7ea67bd 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/histogram.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/histogram.go
@@ -165,7 +165,7 @@ func NewHistogram(opts HistogramOpts) Histogram {
 
 func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram {
 	if len(desc.variableLabels) != len(labelValues) {
-		panic(errInconsistentCardinality)
+		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, labelValues))
 	}
 
 	for _, n := range desc.variableLabels {
@@ -204,8 +204,8 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 			}
 		}
 	}
-	// Finally we know the final length of h.upperBounds and can make counts
-	// for both states:
+	// Finally we know the final length of h.upperBounds and can make buckets
+	// for both counts:
 	h.counts[0].buckets = make([]uint64, len(h.upperBounds))
 	h.counts[1].buckets = make([]uint64, len(h.upperBounds))
 
@@ -224,18 +224,21 @@ type histogramCounts struct {
 }
 
 type histogram struct {
-	// countAndHotIdx is a complicated one. For lock-free yet atomic
-	// observations, we need to save the total count of observations again,
-	// combined with the index of the currently-hot counts struct, so that
-	// we can perform the operation on both values atomically. The least
-	// significant bit defines the hot counts struct. The remaining 63 bits
-	// represent the total count of observations. This happens under the
-	// assumption that the 63bit count will never overflow. Rationale: An
-	// observations takes about 30ns. Let's assume it could happen in
-	// 10ns. Overflowing the counter will then take at least (2^63)*10ns,
-	// which is about 3000 years.
+	// countAndHotIdx enables lock-free writes with use of atomic updates.
+	// The most significant bit is the hot index [0 or 1] of the count field
+	// below. Observe calls update the hot one. All remaining bits count the
+	// number of Observe calls. Observe starts by incrementing this counter,
+	// and finish by incrementing the count field in the respective
+	// histogramCounts, as a marker for completion.
 	//
-	// This has to be first in the struct for 64bit alignment. See
+	// Calls of the Write method (which are non-mutating reads from the
+	// perspective of the histogram) swap the hot–cold under the writeMtx
+	// lock. A cooldown is awaited (while locked) by comparing the number of
+	// observations with the initiation count. Once they match, then the
+	// last observation on the now cool one has completed. All cool fields must
+	// be merged into the new hot before releasing writeMtx.
+	//
+	// Fields with atomic access first! See alignment constraint:
 	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
 	countAndHotIdx uint64
 
@@ -243,16 +246,14 @@ type histogram struct {
 	desc     *Desc
 	writeMtx sync.Mutex // Only used in the Write method.
 
-	upperBounds []float64
-
 	// Two counts, one is "hot" for lock-free observations, the other is
 	// "cold" for writing out a dto.Metric. It has to be an array of
 	// pointers to guarantee 64bit alignment of the histogramCounts, see
 	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG.
 	counts [2]*histogramCounts
-	hotIdx int // Index of currently-hot counts. Only used within Write.
 
-	labelPairs []*dto.LabelPair
+	upperBounds []float64
+	labelPairs  []*dto.LabelPair
 }
 
 func (h *histogram) Desc() *Desc {
@@ -271,11 +272,11 @@ func (h *histogram) Observe(v float64) {
 	// 300 buckets: 154 ns/op linear - binary 61.6 ns/op
 	i := sort.SearchFloat64s(h.upperBounds, v)
 
-	// We increment h.countAndHotIdx by 2 so that the counter in the upper
-	// 63 bits gets incremented by 1. At the same time, we get the new value
+	// We increment h.countAndHotIdx so that the counter in the lower
+	// 63 bits gets incremented. At the same time, we get the new value
 	// back, which we can use to find the currently-hot counts.
-	n := atomic.AddUint64(&h.countAndHotIdx, 2)
-	hotCounts := h.counts[n%2]
+	n := atomic.AddUint64(&h.countAndHotIdx, 1)
+	hotCounts := h.counts[n>>63]
 
 	if i < len(h.upperBounds) {
 		atomic.AddUint64(&hotCounts.buckets[i], 1)
@@ -293,72 +294,43 @@ func (h *histogram) Observe(v float64) {
 }
 
 func (h *histogram) Write(out *dto.Metric) error {
-	var (
-		his                   = &dto.Histogram{}
-		buckets               = make([]*dto.Bucket, len(h.upperBounds))
-		hotCounts, coldCounts *histogramCounts
-		count                 uint64
-	)
-
-	// For simplicity, we mutex the rest of this method. It is not in the
-	// hot path, i.e.  Observe is called much more often than Write. The
-	// complication of making Write lock-free isn't worth it.
+	// For simplicity, we protect this whole method by a mutex. It is not in
+	// the hot path, i.e. Observe is called much more often than Write. The
+	// complication of making Write lock-free isn't worth it, if possible at
+	// all.
 	h.writeMtx.Lock()
 	defer h.writeMtx.Unlock()
 
-	// This is a bit arcane, which is why the following spells out this if
-	// clause in English:
-	//
-	// If the currently-hot counts struct is #0, we atomically increment
-	// h.countAndHotIdx by 1 so that from now on Observe will use the counts
-	// struct #1. Furthermore, the atomic increment gives us the new value,
-	// which, in its most significant 63 bits, tells us the count of
-	// observations done so far up to and including currently ongoing
-	// observations still using the counts struct just changed from hot to
-	// cold. To have a normal uint64 for the count, we bitshift by 1 and
-	// save the result in count. We also set h.hotIdx to 1 for the next
-	// Write call, and we will refer to counts #1 as hotCounts and to counts
-	// #0 as coldCounts.
-	//
-	// If the currently-hot counts struct is #1, we do the corresponding
-	// things the other way round. We have to _decrement_ h.countAndHotIdx
-	// (which is a bit arcane in itself, as we have to express -1 with an
-	// unsigned int...).
-	if h.hotIdx == 0 {
-		count = atomic.AddUint64(&h.countAndHotIdx, 1) >> 1
-		h.hotIdx = 1
-		hotCounts = h.counts[1]
-		coldCounts = h.counts[0]
-	} else {
-		count = atomic.AddUint64(&h.countAndHotIdx, ^uint64(0)) >> 1 // Decrement.
-		h.hotIdx = 0
-		hotCounts = h.counts[0]
-		coldCounts = h.counts[1]
-	}
-
-	// Now we have to wait for the now-declared-cold counts to actually cool
-	// down, i.e. wait for all observations still using it to finish. That's
-	// the case once the count in the cold counts struct is the same as the
-	// one atomically retrieved from the upper 63bits of h.countAndHotIdx.
-	for {
-		if count == atomic.LoadUint64(&coldCounts.count) {
-			break
-		}
+	// Adding 1<<63 switches the hot index (from 0 to 1 or from 1 to 0)
+	// without touching the count bits. See the struct comments for a full
+	// description of the algorithm.
+	n := atomic.AddUint64(&h.countAndHotIdx, 1<<63)
+	// count is contained unchanged in the lower 63 bits.
+	count := n & ((1 << 63) - 1)
+	// The most significant bit tells us which counts is hot. The complement
+	// is thus the cold one.
+	hotCounts := h.counts[n>>63]
+	coldCounts := h.counts[(^n)>>63]
+
+	// Await cooldown.
+	for count != atomic.LoadUint64(&coldCounts.count) {
 		runtime.Gosched() // Let observations get work done.
 	}
 
-	his.SampleCount = proto.Uint64(count)
-	his.SampleSum = proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits)))
+	his := &dto.Histogram{
+		Bucket:      make([]*dto.Bucket, len(h.upperBounds)),
+		SampleCount: proto.Uint64(count),
+		SampleSum:   proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+	}
 	var cumCount uint64
 	for i, upperBound := range h.upperBounds {
 		cumCount += atomic.LoadUint64(&coldCounts.buckets[i])
-		buckets[i] = &dto.Bucket{
+		his.Bucket[i] = &dto.Bucket{
 			CumulativeCount: proto.Uint64(cumCount),
 			UpperBound:      proto.Float64(upperBound),
 		}
 	}
 
-	his.Bucket = buckets
 	out.Histogram = his
 	out.Label = h.labelPairs
 
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/http.go b/vendor/github.com/prometheus/client_golang/prometheus/http.go
index 4b8e6027..19a3e8f4 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/http.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/http.go
@@ -15,9 +15,7 @@ package prometheus
 
 import (
 	"bufio"
-	"bytes"
 	"compress/gzip"
-	"fmt"
 	"io"
 	"net"
 	"net/http"
@@ -36,24 +34,14 @@ import (
 
 const (
 	contentTypeHeader     = "Content-Type"
-	contentLengthHeader   = "Content-Length"
 	contentEncodingHeader = "Content-Encoding"
 	acceptEncodingHeader  = "Accept-Encoding"
 )
 
-var bufPool sync.Pool
-
-func getBuf() *bytes.Buffer {
-	buf := bufPool.Get()
-	if buf == nil {
-		return &bytes.Buffer{}
-	}
-	return buf.(*bytes.Buffer)
-}
-
-func giveBuf(buf *bytes.Buffer) {
-	buf.Reset()
-	bufPool.Put(buf)
+var gzipPool = sync.Pool{
+	New: func() interface{} {
+		return gzip.NewWriter(nil)
+	},
 }
 
 // Handler returns an HTTP handler for the DefaultGatherer. It is
@@ -71,58 +59,40 @@ func Handler() http.Handler {
 // Deprecated: Use promhttp.HandlerFor(DefaultGatherer, promhttp.HandlerOpts{})
 // instead. See there for further documentation.
 func UninstrumentedHandler() http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+	return http.HandlerFunc(func(rsp http.ResponseWriter, req *http.Request) {
 		mfs, err := DefaultGatherer.Gather()
 		if err != nil {
-			http.Error(w, "An error has occurred during metrics collection:\n\n"+err.Error(), http.StatusInternalServerError)
+			httpError(rsp, err)
 			return
 		}
 
 		contentType := expfmt.Negotiate(req.Header)
-		buf := getBuf()
-		defer giveBuf(buf)
-		writer, encoding := decorateWriter(req, buf)
-		enc := expfmt.NewEncoder(writer, contentType)
-		var lastErr error
+		header := rsp.Header()
+		header.Set(contentTypeHeader, string(contentType))
+
+		w := io.Writer(rsp)
+		if gzipAccepted(req.Header) {
+			header.Set(contentEncodingHeader, "gzip")
+			gz := gzipPool.Get().(*gzip.Writer)
+			defer gzipPool.Put(gz)
+
+			gz.Reset(w)
+			defer gz.Close()
+
+			w = gz
+		}
+
+		enc := expfmt.NewEncoder(w, contentType)
+
 		for _, mf := range mfs {
 			if err := enc.Encode(mf); err != nil {
-				lastErr = err
-				http.Error(w, "An error has occurred during metrics encoding:\n\n"+err.Error(), http.StatusInternalServerError)
+				httpError(rsp, err)
 				return
 			}
 		}
-		if closer, ok := writer.(io.Closer); ok {
-			closer.Close()
-		}
-		if lastErr != nil && buf.Len() == 0 {
-			http.Error(w, "No metrics encoded, last error:\n\n"+lastErr.Error(), http.StatusInternalServerError)
-			return
-		}
-		header := w.Header()
-		header.Set(contentTypeHeader, string(contentType))
-		header.Set(contentLengthHeader, fmt.Sprint(buf.Len()))
-		if encoding != "" {
-			header.Set(contentEncodingHeader, encoding)
-		}
-		w.Write(buf.Bytes())
 	})
 }
 
-// decorateWriter wraps a writer to handle gzip compression if requested.  It
-// returns the decorated writer and the appropriate "Content-Encoding" header
-// (which is empty if no compression is enabled).
-func decorateWriter(request *http.Request, writer io.Writer) (io.Writer, string) {
-	header := request.Header.Get(acceptEncodingHeader)
-	parts := strings.Split(header, ",")
-	for _, part := range parts {
-		part = strings.TrimSpace(part)
-		if part == "gzip" || strings.HasPrefix(part, "gzip;") {
-			return gzip.NewWriter(writer), "gzip"
-		}
-	}
-	return writer, ""
-}
-
 var instLabels = []string{"method", "code"}
 
 type nower interface {
@@ -360,6 +330,8 @@ type fancyResponseWriterDelegator struct {
 }
 
 func (f *fancyResponseWriterDelegator) CloseNotify() <-chan bool {
+	//lint:ignore SA1019 http.CloseNotifier is deprecated but we don't want to
+	//remove support from client_golang yet.
 	return f.ResponseWriter.(http.CloseNotifier).CloseNotify()
 }
 
@@ -503,3 +475,31 @@ func sanitizeCode(s int) string {
 		return strconv.Itoa(s)
 	}
 }
+
+// gzipAccepted returns whether the client will accept gzip-encoded content.
+func gzipAccepted(header http.Header) bool {
+	a := header.Get(acceptEncodingHeader)
+	parts := strings.Split(a, ",")
+	for _, part := range parts {
+		part = strings.TrimSpace(part)
+		if part == "gzip" || strings.HasPrefix(part, "gzip;") {
+			return true
+		}
+	}
+	return false
+}
+
+// httpError removes any content-encoding header and then calls http.Error with
+// the provided error and http.StatusInternalServerErrer. Error contents is
+// supposed to be uncompressed plain text. However, same as with a plain
+// http.Error, any header settings will be void if the header has already been
+// sent. The error message will still be written to the writer, but it will
+// probably be of limited use.
+func httpError(rsp http.ResponseWriter, err error) {
+	rsp.Header().Del(contentEncodingHeader)
+	http.Error(
+		rsp,
+		"An error has occurred while serving metrics:\n\n"+err.Error(),
+		http.StatusInternalServerError,
+	)
+}
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/labels.go b/vendor/github.com/prometheus/client_golang/prometheus/labels.go
index e68f132e..2744443a 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/labels.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/labels.go
@@ -37,9 +37,22 @@ const reservedLabelPrefix = "__"
 
 var errInconsistentCardinality = errors.New("inconsistent label cardinality")
 
+func makeInconsistentCardinalityError(fqName string, labels, labelValues []string) error {
+	return fmt.Errorf(
+		"%s: %q has %d variable labels named %q but %d values %q were provided",
+		errInconsistentCardinality, fqName,
+		len(labels), labels,
+		len(labelValues), labelValues,
+	)
+}
+
 func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
 	if len(labels) != expectedNumberOfValues {
-		return errInconsistentCardinality
+		return fmt.Errorf(
+			"%s: expected %d label values but got %d in %#v",
+			errInconsistentCardinality, expectedNumberOfValues,
+			len(labels), labels,
+		)
 	}
 
 	for name, val := range labels {
@@ -53,7 +66,11 @@ func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
 
 func validateLabelValues(vals []string, expectedNumberOfValues int) error {
 	if len(vals) != expectedNumberOfValues {
-		return errInconsistentCardinality
+		return fmt.Errorf(
+			"%s: expected %d label values but got %d in %#v",
+			errInconsistentCardinality, expectedNumberOfValues,
+			len(vals), vals,
+		)
 	}
 
 	for _, val := range vals {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/registry.go b/vendor/github.com/prometheus/client_golang/prometheus/registry.go
index e422ef38..f2fb67ae 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/registry.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/registry.go
@@ -16,6 +16,9 @@ package prometheus
 import (
 	"bytes"
 	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
 	"runtime"
 	"sort"
 	"strings"
@@ -23,6 +26,7 @@ import (
 	"unicode/utf8"
 
 	"github.com/golang/protobuf/proto"
+	"github.com/prometheus/common/expfmt"
 
 	dto "github.com/prometheus/client_model/go"
 
@@ -533,6 +537,38 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 	return internal.NormalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
 }
 
+// WriteToTextfile calls Gather on the provided Gatherer, encodes the result in the
+// Prometheus text format, and writes it to a temporary file. Upon success, the
+// temporary file is renamed to the provided filename.
+//
+// This is intended for use with the textfile collector of the node exporter.
+// Note that the node exporter expects the filename to be suffixed with ".prom".
+func WriteToTextfile(filename string, g Gatherer) error {
+	tmp, err := ioutil.TempFile(filepath.Dir(filename), filepath.Base(filename))
+	if err != nil {
+		return err
+	}
+	defer os.Remove(tmp.Name())
+
+	mfs, err := g.Gather()
+	if err != nil {
+		return err
+	}
+	for _, mf := range mfs {
+		if _, err := expfmt.MetricFamilyToText(tmp, mf); err != nil {
+			return err
+		}
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+
+	if err := os.Chmod(tmp.Name(), 0644); err != nil {
+		return err
+	}
+	return os.Rename(tmp.Name(), filename)
+}
+
 // processMetric is an internal helper method only used by the Gather method.
 func processMetric(
 	metric Metric,
@@ -644,7 +680,7 @@ func processMetric(
 // 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
-// Gather calles are all returned in a flattened MultiError. Duplicate and
+// Gather calls are all returned in a flattened MultiError. Duplicate and
 // inconsistent Metrics are skipped (first occurrence in slice order wins) and
 // reported in the returned error.
 //
@@ -836,7 +872,13 @@ func checkMetricConsistency(
 	h = hashAddByte(h, separatorByte)
 	// Make sure label pairs are sorted. We depend on it for the consistency
 	// check.
-	sort.Sort(labelPairSorter(dtoMetric.Label))
+	if !sort.IsSorted(labelPairSorter(dtoMetric.Label)) {
+		// We cannot sort dtoMetric.Label in place as it is immutable by contract.
+		copiedLabels := make([]*dto.LabelPair, len(dtoMetric.Label))
+		copy(copiedLabels, dtoMetric.Label)
+		sort.Sort(labelPairSorter(copiedLabels))
+		dtoMetric.Label = copiedLabels
+	}
 	for _, lp := range dtoMetric.Label {
 		h = hashAdd(h, lp.GetName())
 		h = hashAddByte(h, separatorByte)
@@ -867,8 +909,8 @@ func checkDescConsistency(
 	}
 
 	// Is the desc consistent with the content of the metric?
-	lpsFromDesc := make([]*dto.LabelPair, 0, len(dtoMetric.Label))
-	lpsFromDesc = append(lpsFromDesc, desc.constLabelPairs...)
+	lpsFromDesc := make([]*dto.LabelPair, len(desc.constLabelPairs), len(dtoMetric.Label))
+	copy(lpsFromDesc, desc.constLabelPairs)
 	for _, l := range desc.variableLabels {
 		lpsFromDesc = append(lpsFromDesc, &dto.LabelPair{
 			Name: proto.String(l),
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/summary.go b/vendor/github.com/prometheus/client_golang/prometheus/summary.go
index f7e92d82..1574b0fe 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/summary.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/summary.go
@@ -16,8 +16,10 @@ package prometheus
 import (
 	"fmt"
 	"math"
+	"runtime"
 	"sort"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/beorn7/perks/quantile"
@@ -125,9 +127,10 @@ type SummaryOpts struct {
 	// its zero value (i.e. nil). To create a Summary without Objectives,
 	// set it to an empty map (i.e. map[float64]float64{}).
 	//
-	// Deprecated: Note that the current value of DefObjectives is
-	// deprecated. It will be replaced by an empty map in v0.10 of the
-	// library. Please explicitly set Objectives to the desired value.
+	// Note that the current value of DefObjectives is deprecated. It will
+	// be replaced by an empty map in v0.10 of the library. Please
+	// explicitly set Objectives to the desired value to avoid problems
+	// during the transition.
 	Objectives map[float64]float64
 
 	// MaxAge defines the duration for which an observation stays relevant
@@ -151,7 +154,7 @@ type SummaryOpts struct {
 	BufCap uint32
 }
 
-// Great fuck-up with the sliding-window decay algorithm... The Merge method of
+// Problem with the sliding-window decay algorithm... The Merge method of
 // perk/quantile is actually not working as advertised - and it might be
 // unfixable, as the underlying algorithm is apparently not capable of merging
 // summaries in the first place. To avoid using Merge, we are currently adding
@@ -181,7 +184,7 @@ func NewSummary(opts SummaryOpts) Summary {
 
 func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 	if len(desc.variableLabels) != len(labelValues) {
-		panic(errInconsistentCardinality)
+		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, labelValues))
 	}
 
 	for _, n := range desc.variableLabels {
@@ -214,6 +217,17 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 		opts.BufCap = DefBufCap
 	}
 
+	if len(opts.Objectives) == 0 {
+		// Use the lock-free implementation of a Summary without objectives.
+		s := &noObjectivesSummary{
+			desc:       desc,
+			labelPairs: makeLabelPairs(desc, labelValues),
+			counts:     [2]*summaryCounts{&summaryCounts{}, &summaryCounts{}},
+		}
+		s.init(s) // Init self-collection.
+		return s
+	}
+
 	s := &summary{
 		desc: desc,
 
@@ -382,6 +396,116 @@ func (s *summary) swapBufs(now time.Time) {
 	}
 }
 
+type summaryCounts struct {
+	// sumBits contains the bits of the float64 representing the sum of all
+	// observations. sumBits and count have to go first in the struct to
+	// guarantee alignment for atomic operations.
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	sumBits uint64
+	count   uint64
+}
+
+type noObjectivesSummary struct {
+	// countAndHotIdx enables lock-free writes with use of atomic updates.
+	// The most significant bit is the hot index [0 or 1] of the count field
+	// below. Observe calls update the hot one. All remaining bits count the
+	// number of Observe calls. Observe starts by incrementing this counter,
+	// and finish by incrementing the count field in the respective
+	// summaryCounts, as a marker for completion.
+	//
+	// Calls of the Write method (which are non-mutating reads from the
+	// perspective of the summary) swap the hot–cold under the writeMtx
+	// lock. A cooldown is awaited (while locked) by comparing the number of
+	// observations with the initiation count. Once they match, then the
+	// last observation on the now cool one has completed. All cool fields must
+	// be merged into the new hot before releasing writeMtx.
+
+	// Fields with atomic access first! See alignment constraint:
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	countAndHotIdx uint64
+
+	selfCollector
+	desc     *Desc
+	writeMtx sync.Mutex // Only used in the Write method.
+
+	// Two counts, one is "hot" for lock-free observations, the other is
+	// "cold" for writing out a dto.Metric. It has to be an array of
+	// pointers to guarantee 64bit alignment of the histogramCounts, see
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG.
+	counts [2]*summaryCounts
+
+	labelPairs []*dto.LabelPair
+}
+
+func (s *noObjectivesSummary) Desc() *Desc {
+	return s.desc
+}
+
+func (s *noObjectivesSummary) Observe(v float64) {
+	// We increment h.countAndHotIdx so that the counter in the lower
+	// 63 bits gets incremented. At the same time, we get the new value
+	// back, which we can use to find the currently-hot counts.
+	n := atomic.AddUint64(&s.countAndHotIdx, 1)
+	hotCounts := s.counts[n>>63]
+
+	for {
+		oldBits := atomic.LoadUint64(&hotCounts.sumBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
+		if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
+			break
+		}
+	}
+	// Increment count last as we take it as a signal that the observation
+	// is complete.
+	atomic.AddUint64(&hotCounts.count, 1)
+}
+
+func (s *noObjectivesSummary) Write(out *dto.Metric) error {
+	// For simplicity, we protect this whole method by a mutex. It is not in
+	// the hot path, i.e. Observe is called much more often than Write. The
+	// complication of making Write lock-free isn't worth it, if possible at
+	// all.
+	s.writeMtx.Lock()
+	defer s.writeMtx.Unlock()
+
+	// Adding 1<<63 switches the hot index (from 0 to 1 or from 1 to 0)
+	// without touching the count bits. See the struct comments for a full
+	// description of the algorithm.
+	n := atomic.AddUint64(&s.countAndHotIdx, 1<<63)
+	// count is contained unchanged in the lower 63 bits.
+	count := n & ((1 << 63) - 1)
+	// The most significant bit tells us which counts is hot. The complement
+	// is thus the cold one.
+	hotCounts := s.counts[n>>63]
+	coldCounts := s.counts[(^n)>>63]
+
+	// Await cooldown.
+	for count != atomic.LoadUint64(&coldCounts.count) {
+		runtime.Gosched() // Let observations get work done.
+	}
+
+	sum := &dto.Summary{
+		SampleCount: proto.Uint64(count),
+		SampleSum:   proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+	}
+
+	out.Summary = sum
+	out.Label = s.labelPairs
+
+	// Finally add all the cold counts to the new hot counts and reset the cold counts.
+	atomic.AddUint64(&hotCounts.count, count)
+	atomic.StoreUint64(&coldCounts.count, 0)
+	for {
+		oldBits := atomic.LoadUint64(&hotCounts.sumBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + sum.GetSampleSum())
+		if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
+			atomic.StoreUint64(&coldCounts.sumBits, 0)
+			break
+		}
+	}
+	return nil
+}
+
 type quantSort []*dto.Quantile
 
 func (s quantSort) Len() int {
diff --git a/vendor/github.com/prometheus/client_golang/prometheus/timer.go b/vendor/github.com/prometheus/client_golang/prometheus/timer.go
index b8fc5f18..8d5f1052 100644
--- a/vendor/github.com/prometheus/client_golang/prometheus/timer.go
+++ b/vendor/github.com/prometheus/client_golang/prometheus/timer.go
@@ -39,13 +39,16 @@ func NewTimer(o Observer) *Timer {
 
 // ObserveDuration records the duration passed since the Timer was created with
 // NewTimer. It calls the Observe method of the Observer provided during
-// construction with the duration in seconds as an argument. ObserveDuration is
-// usually called with a defer statement.
+// construction with the duration in seconds as an argument. The observed
+// duration is also returned. ObserveDuration is usually called with a defer
+// statement.
 //
 // Note that this method is only guaranteed to never observe negative durations
 // if used with Go1.9+.
-func (t *Timer) ObserveDuration() {
+func (t *Timer) ObserveDuration() time.Duration {
+	d := time.Since(t.begin)
 	if t.observer != nil {
-		t.observer.Observe(time.Since(t.begin).Seconds())
+		t.observer.Observe(d.Seconds())
 	}
+	return d
 }
diff --git a/vendor/vendor.json b/vendor/vendor.json
index 2b2f1420..cfcc297f 100644
--- a/vendor/vendor.json
+++ b/vendor/vendor.json
@@ -207,12 +207,12 @@
 			"revisionTime": "2018-01-27T01:58:12Z"
 		},
 		{
-			"checksumSHA1": "frS661rlSEZWE9CezHhnFioQK/I=",
+			"checksumSHA1": "5d1E/NDh6XDKBifjiyJt9p5W9cs=",
 			"path": "github.com/prometheus/client_golang/prometheus",
-			"revision": "1cafe34db7fdec6022e17e00e1c1ea501022f3e4",
-			"revisionTime": "2018-10-15T14:52:39Z",
-			"version": "v0.9",
-			"versionExact": "v0.9.0"
+			"revision": "50c4339db732beb2165735d2cde0bff78eb3c5a5",
+			"revisionTime": "2019-05-16T21:22:10Z",
+			"version": "v0.9.3",
+			"versionExact": "v0.9.3"
 		},
 		{
 			"checksumSHA1": "UBqhkyjCz47+S19MVTigxJ2VjVQ=",