diff --git a/vendor/github.com/prometheus/tsdb/compact.go b/vendor/github.com/prometheus/tsdb/compact.go
index 7d8174f0d..a3bc7d17a 100644
--- a/vendor/github.com/prometheus/tsdb/compact.go
+++ b/vendor/github.com/prometheus/tsdb/compact.go
@@ -17,7 +17,6 @@ import (
 	"math/rand"
 	"os"
 	"path/filepath"
-	"runtime"
 	"sort"
 	"time"
 
@@ -365,10 +364,6 @@ func (c *LeveledCompactor) write(dest string, meta *BlockMeta, blocks ...BlockRe
 		}
 		c.metrics.ran.Inc()
 		c.metrics.duration.Observe(time.Since(t).Seconds())
-
-		// We might have done quite a few allocs. Enforce a GC so they do not accumulate
-		// with subsequent compactions or head GCs.
-		runtime.GC()
 	}(time.Now())
 
 	dir := filepath.Join(dest, meta.ULID.String())
@@ -570,14 +565,6 @@ func (c *LeveledCompactor) populateBlock(blocks []BlockReader, meta *BlockMeta,
 			return errors.Wrap(err, "write postings")
 		}
 	}
-	// Write a postings list containing all series.
-	all := make([]uint64, i)
-	for i := range all {
-		all[i] = uint64(i)
-	}
-	if err := indexw.WritePostings("", "", newListPostings(all)); err != nil {
-		return errors.Wrap(err, "write 'all' postings")
-	}
 
 	return nil
 }
diff --git a/vendor/github.com/prometheus/tsdb/db.go b/vendor/github.com/prometheus/tsdb/db.go
index ad034d8b0..c9745cfc6 100644
--- a/vendor/github.com/prometheus/tsdb/db.go
+++ b/vendor/github.com/prometheus/tsdb/db.go
@@ -21,6 +21,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 	"sort"
 	"strconv"
 	"sync"
@@ -349,9 +350,12 @@ func (db *DB) compact() (changes bool, err error) {
 		}
 		changes = true
 
+		runtime.GC()
+
 		if err := db.reload(); err != nil {
 			return changes, errors.Wrap(err, "reload blocks")
 		}
+		runtime.GC()
 	}
 
 	// Check for compactions of multiple blocks.
@@ -380,10 +384,12 @@ func (db *DB) compact() (changes bool, err error) {
 				return changes, errors.Wrap(err, "delete compacted block")
 			}
 		}
+		runtime.GC()
 
 		if err := db.reload(); err != nil {
 			return changes, errors.Wrap(err, "reload blocks")
 		}
+		runtime.GC()
 	}
 
 	return changes, nil
diff --git a/vendor/github.com/prometheus/tsdb/encoding_helpers.go b/vendor/github.com/prometheus/tsdb/encoding_helpers.go
index 9aa4ba409..17c3ff081 100644
--- a/vendor/github.com/prometheus/tsdb/encoding_helpers.go
+++ b/vendor/github.com/prometheus/tsdb/encoding_helpers.go
@@ -77,6 +77,22 @@ func (d *decbuf) uvarint32() uint32 { return uint32(d.uvarint64()) }
 func (d *decbuf) be32int() int      { return int(d.be32()) }
 func (d *decbuf) be64int64() int64  { return int64(d.be64()) }
 
+// uvarintTempStr decodes like uvarintStr but the returned string is
+// not safe to use if the underyling buffer changes.
+func (d *decbuf) uvarintTempStr() string {
+	l := d.uvarint64()
+	if d.e != nil {
+		return ""
+	}
+	if len(d.b) < int(l) {
+		d.e = errInvalidSize
+		return ""
+	}
+	s := yoloString(d.b[:l])
+	d.b = d.b[l:]
+	return s
+}
+
 func (d *decbuf) uvarintStr() string {
 	l := d.uvarint64()
 	if d.e != nil {
diff --git a/vendor/github.com/prometheus/tsdb/head.go b/vendor/github.com/prometheus/tsdb/head.go
index a74552bca..ea7b63f8a 100644
--- a/vendor/github.com/prometheus/tsdb/head.go
+++ b/vendor/github.com/prometheus/tsdb/head.go
@@ -15,7 +15,6 @@ package tsdb
 
 import (
 	"math"
-	"runtime"
 	"sort"
 	"sync"
 	"sync/atomic"
@@ -402,10 +401,13 @@ func (a *headAppender) AddFast(ref uint64, t int64, v float64) error {
 	if s == nil {
 		return errors.Wrap(ErrNotFound, "unknown series")
 	}
-	if err := s.appendable(t, v); err != nil {
+	s.Lock()
+	err := s.appendable(t, v)
+	s.Unlock()
+
+	if err != nil {
 		return err
 	}
-
 	if t < a.mint {
 		return ErrOutOfBounds
 	}
@@ -435,7 +437,10 @@ func (a *headAppender) Commit() error {
 	total := len(a.samples)
 
 	for _, s := range a.samples {
+		s.series.Lock()
 		ok, chunkCreated := s.series.append(s.T, s.V)
+		s.series.Unlock()
+
 		if !ok {
 			total--
 		}
@@ -509,8 +514,6 @@ Outer:
 
 // gc removes data before the minimum timestmap from the head.
 func (h *Head) gc() {
-	defer runtime.GC()
-
 	// Only data strictly lower than this timestamp must be deleted.
 	mint := h.MinTime()
 
@@ -672,9 +675,9 @@ func (h *headChunkReader) Chunk(ref uint64) (chunks.Chunk, error) {
 
 	s := h.head.series.getByID(sid)
 
-	s.mtx.RLock()
+	s.Lock()
 	c := s.chunk(int(cid))
-	s.mtx.RUnlock()
+	s.Unlock()
 
 	// Do not expose chunks that are outside of the specified range.
 	if c == nil || !intervalOverlap(c.minTime, c.maxTime, h.mint, h.maxt) {
@@ -694,9 +697,10 @@ type safeChunk struct {
 }
 
 func (c *safeChunk) Iterator() chunks.Iterator {
-	c.s.mtx.RLock()
-	defer c.s.mtx.RUnlock()
-	return c.s.iterator(c.cid)
+	c.s.Lock()
+	it := c.s.iterator(c.cid)
+	c.s.Unlock()
+	return it
 }
 
 // func (c *safeChunk) Appender() (chunks.Appender, error) { panic("illegal") }
@@ -803,8 +807,8 @@ func (h *headIndexReader) Series(ref uint64, lbls *labels.Labels, chks *[]ChunkM
 	}
 	*lbls = append((*lbls)[:0], s.lset...)
 
-	s.mtx.RLock()
-	defer s.mtx.RUnlock()
+	s.Lock()
+	defer s.Unlock()
 
 	*chks = (*chks)[:0]
 
@@ -956,11 +960,11 @@ func (s *stripeSeries) gc(mint int64) (map[uint64]struct{}, int) {
 
 		for hash, all := range s.hashes[i] {
 			for _, series := range all {
-				series.mtx.Lock()
+				series.Lock()
 				rmChunks += series.truncateChunksBefore(mint)
 
 				if len(series.chunks) > 0 {
-					series.mtx.Unlock()
+					series.Unlock()
 					continue
 				}
 
@@ -983,7 +987,7 @@ func (s *stripeSeries) gc(mint int64) (map[uint64]struct{}, int) {
 					s.locks[j].Unlock()
 				}
 
-				series.mtx.Unlock()
+				series.Unlock()
 			}
 		}
 
@@ -1040,8 +1044,10 @@ type sample struct {
 	v float64
 }
 
+// memSeries is the in-memory representation of a series. None of its methods
+// are goroutine safe and its the callers responsibility to lock it.
 type memSeries struct {
-	mtx sync.RWMutex
+	sync.Mutex
 
 	ref          uint64
 	lset         labels.Labels
@@ -1143,8 +1149,6 @@ func (s *memSeries) truncateChunksBefore(mint int64) (removed int) {
 func (s *memSeries) append(t int64, v float64) (success, chunkCreated bool) {
 	const samplesPerChunk = 120
 
-	s.mtx.Lock()
-
 	c := s.head()
 
 	if c == nil {
@@ -1152,7 +1156,6 @@ func (s *memSeries) append(t int64, v float64) (success, chunkCreated bool) {
 		chunkCreated = true
 	}
 	if c.maxTime >= t {
-		s.mtx.Unlock()
 		return false, chunkCreated
 	}
 	if c.chunk.NumSamples() > samplesPerChunk/4 && t >= s.nextAt {
@@ -1175,8 +1178,6 @@ func (s *memSeries) append(t int64, v float64) (success, chunkCreated bool) {
 	s.sampleBuf[2] = s.sampleBuf[3]
 	s.sampleBuf[3] = sample{t: t, v: v}
 
-	s.mtx.Unlock()
-
 	return true, chunkCreated
 }
 
diff --git a/vendor/github.com/prometheus/tsdb/index.go b/vendor/github.com/prometheus/tsdb/index.go
index ddc2c4f52..fd9b25162 100644
--- a/vendor/github.com/prometheus/tsdb/index.go
+++ b/vendor/github.com/prometheus/tsdb/index.go
@@ -292,10 +292,22 @@ func (w *indexWriter) AddSeries(ref uint64, lset labels.Labels, chunks ...ChunkM
 
 	w.buf2.putUvarint(len(chunks))
 
-	for _, c := range chunks {
+	if len(chunks) > 0 {
+		c := chunks[0]
 		w.buf2.putVarint64(c.MinTime)
-		w.buf2.putVarint64(c.MaxTime)
+		w.buf2.putUvarint64(uint64(c.MaxTime - c.MinTime))
 		w.buf2.putUvarint64(c.Ref)
+		t0 := c.MaxTime
+		ref0 := int64(c.Ref)
+
+		for _, c := range chunks[1:] {
+			w.buf2.putUvarint64(uint64(c.MinTime - t0))
+			w.buf2.putUvarint64(uint64(c.MaxTime - c.MinTime))
+			t0 = c.MaxTime
+
+			w.buf2.putVarint64(int64(c.Ref) - ref0)
+			ref0 = int64(c.Ref)
+		}
 	}
 
 	w.buf1.reset()
@@ -335,10 +347,6 @@ func (w *indexWriter) AddSymbols(sym map[string]struct{}) error {
 
 	for _, s := range symbols {
 		w.symbols[s] = uint32(w.pos) + headerSize + uint32(w.buf2.len())
-
-		// NOTE: len(s) gives the number of runes, not the number of bytes.
-		// Therefore the read-back length for strings with unicode characters will
-		// be off when not using putUvarintStr.
 		w.buf2.putUvarintStr(s)
 	}
 
@@ -636,7 +644,7 @@ func (r *indexReader) readOffsetTable(off uint64) (map[string]uint32, error) {
 		keys := make([]string, 0, keyCount)
 
 		for i := 0; i < keyCount; i++ {
-			keys = append(keys, d2.uvarintStr())
+			keys = append(keys, d2.uvarintTempStr())
 		}
 		res[strings.Join(keys, sep)] = uint32(d2.uvarint())
 
@@ -673,7 +681,7 @@ func (r *indexReader) section(o uint32) (byte, []byte, error) {
 func (r *indexReader) lookupSymbol(o uint32) (string, error) {
 	d := r.decbufAt(int(o))
 
-	s := d.uvarintStr()
+	s := d.uvarintTempStr()
 	if d.err() != nil {
 		return "", errors.Wrapf(d.err(), "read symbol at %d", o)
 	}
@@ -688,7 +696,7 @@ func (r *indexReader) Symbols() (map[string]struct{}, error) {
 	sym := make(map[string]struct{}, count)
 
 	for ; count > 0; count-- {
-		s := d2.uvarintStr()
+		s := d2.uvarintTempStr()
 		sym[s] = struct{}{}
 	}
 
@@ -775,17 +783,34 @@ func (r *indexReader) Series(ref uint64, lbls *labels.Labels, chks *[]ChunkMeta)
 	// Read the chunks meta data.
 	k = int(d2.uvarint())
 
-	for i := 0; i < k; i++ {
-		mint := d2.varint64()
-		maxt := d2.varint64()
-		off := d2.uvarint64()
+	if k == 0 {
+		return nil
+	}
+
+	t0 := d2.varint64()
+	maxt := int64(d2.uvarint64()) + t0
+	ref0 := int64(d2.uvarint64())
+
+	*chks = append(*chks, ChunkMeta{
+		Ref:     uint64(ref0),
+		MinTime: t0,
+		MaxTime: maxt,
+	})
+	t0 = maxt
+
+	for i := 1; i < k; i++ {
+		mint := int64(d2.uvarint64()) + t0
+		maxt := int64(d2.uvarint64()) + mint
+
+		ref0 += d2.varint64()
+		t0 = maxt
 
 		if d2.err() != nil {
 			return errors.Wrapf(d2.err(), "read meta for chunk %d", i)
 		}
 
 		*chks = append(*chks, ChunkMeta{
-			Ref:     off,
+			Ref:     uint64(ref0),
 			MinTime: mint,
 			MaxTime: maxt,
 		})
diff --git a/vendor/github.com/prometheus/tsdb/wal.go b/vendor/github.com/prometheus/tsdb/wal.go
index 1dadc8f2c..9af9a1853 100644
--- a/vendor/github.com/prometheus/tsdb/wal.go
+++ b/vendor/github.com/prometheus/tsdb/wal.go
@@ -52,13 +52,16 @@ const (
 	WALEntryDeletes WALEntryType = 4
 )
 
-// SamplesCB is the callback after reading samples.
+// SamplesCB is the callback after reading samples. The passed slice
+// is only valid until the call returns.
 type SamplesCB func([]RefSample) error
 
-// SeriesCB is the callback after reading series.
+// SeriesCB is the callback after reading series. The passed slice
+// is only valid until the call returns.
 type SeriesCB func([]RefSeries) error
 
-// DeletesCB is the callback after reading deletes.
+// DeletesCB is the callback after reading deletes. The passed slice
+// is only valid until the call returns.
 type DeletesCB func([]Stone) error
 
 // WAL is a write ahead log that can log new series labels and samples.
@@ -395,6 +398,10 @@ func (w *SegmentWAL) LogSeries(series []RefSeries) error {
 	buf := w.getBuffer()
 
 	flag := w.encodeSeries(buf, series)
+
+	w.mtx.Lock()
+	defer w.mtx.Unlock()
+
 	err := w.write(WALEntrySeries, flag, buf.get())
 
 	w.putBuffer(buf)
@@ -410,10 +417,6 @@ func (w *SegmentWAL) LogSeries(series []RefSeries) error {
 			tf.minSeries = s.Ref
 		}
 	}
-
-	if w.flushInterval <= 0 {
-		return errors.Wrap(w.Sync(), "sync")
-	}
 	return nil
 }
 
@@ -422,6 +425,10 @@ func (w *SegmentWAL) LogSamples(samples []RefSample) error {
 	buf := w.getBuffer()
 
 	flag := w.encodeSamples(buf, samples)
+
+	w.mtx.Lock()
+	defer w.mtx.Unlock()
+
 	err := w.write(WALEntrySamples, flag, buf.get())
 
 	w.putBuffer(buf)
@@ -436,10 +443,6 @@ func (w *SegmentWAL) LogSamples(samples []RefSample) error {
 			tf.maxTime = s.T
 		}
 	}
-
-	if w.flushInterval <= 0 {
-		return errors.Wrap(w.Sync(), "sync")
-	}
 	return nil
 }
 
@@ -448,6 +451,10 @@ func (w *SegmentWAL) LogDeletes(stones []Stone) error {
 	buf := w.getBuffer()
 
 	flag := w.encodeDeletes(buf, stones)
+
+	w.mtx.Lock()
+	defer w.mtx.Unlock()
+
 	err := w.write(WALEntryDeletes, flag, buf.get())
 
 	w.putBuffer(buf)
@@ -464,10 +471,6 @@ func (w *SegmentWAL) LogDeletes(stones []Stone) error {
 			}
 		}
 	}
-
-	if w.flushInterval <= 0 {
-		return errors.Wrap(w.Sync(), "sync")
-	}
 	return nil
 }
 
@@ -522,19 +525,26 @@ func (w *SegmentWAL) createSegmentFile(name string) (*os.File, error) {
 func (w *SegmentWAL) cut() error {
 	// Sync current head to disk and close.
 	if hf := w.head(); hf != nil {
-		if err := w.sync(); err != nil {
-			return err
-		}
-		off, err := hf.Seek(0, os.SEEK_CUR)
-		if err != nil {
-			return err
-		}
-		if err := hf.Truncate(off); err != nil {
-			return err
-		}
-		if err := hf.Close(); err != nil {
+		if err := w.flush(); err != nil {
 			return err
 		}
+		// Finish last segment asynchronously to not block the WAL moving along
+		// in the new segment.
+		go func() {
+			off, err := hf.Seek(0, os.SEEK_CUR)
+			if err != nil {
+				w.logger.Log("msg", "finish old segment", "segment", hf.Name(), "err", err)
+			}
+			if err := hf.Truncate(off); err != nil {
+				w.logger.Log("msg", "finish old segment", "segment", hf.Name(), "err", err)
+			}
+			if err := hf.Sync(); err != nil {
+				w.logger.Log("msg", "finish old segment", "segment", hf.Name(), "err", err)
+			}
+			if err := hf.Close(); err != nil {
+				w.logger.Log("msg", "finish old segment", "segment", hf.Name(), "err", err)
+			}
+		}()
 	}
 
 	p, _, err := nextSequenceFile(w.dirFile.Name())
@@ -546,9 +556,11 @@ func (w *SegmentWAL) cut() error {
 		return err
 	}
 
-	if err = w.dirFile.Sync(); err != nil {
-		return err
-	}
+	go func() {
+		if err = w.dirFile.Sync(); err != nil {
+			w.logger.Log("msg", "sync WAL directory", "err", err)
+		}
+	}()
 
 	w.files = append(w.files, newSegmentFile(f))
 
@@ -594,6 +606,9 @@ func (w *SegmentWAL) sync() error {
 	if err := w.flush(); err != nil {
 		return err
 	}
+	if w.head() == nil {
+		return nil
+	}
 	return fileutil.Fdatasync(w.head().File)
 }
 
@@ -655,8 +670,6 @@ const (
 )
 
 func (w *SegmentWAL) write(t WALEntryType, flag uint8, buf []byte) error {
-	w.mtx.Lock()
-	defer w.mtx.Unlock()
 	// Cut to the next segment if the entry exceeds the file size unless it would also
 	// exceed the size of a new segment.
 	// TODO(gouthamve): Add a test for this case where the commit is greater than segmentSize.
@@ -769,6 +782,10 @@ type walReader struct {
 	curBuf     []byte
 	lastOffset int64 // offset after last successfully read entry
 
+	seriesBuf    []RefSeries
+	sampleBuf    []RefSample
+	tombstoneBuf []Stone
+
 	err error
 }
 
@@ -996,7 +1013,8 @@ func (r *walReader) entry(cr io.Reader) (WALEntryType, byte, []byte, error) {
 }
 
 func (r *walReader) decodeSeries(flag byte, b []byte) ([]RefSeries, error) {
-	series := []RefSeries{}
+	r.seriesBuf = r.seriesBuf[:0]
+
 	dec := decbuf{b: b}
 
 	for len(dec.b) > 0 && dec.err() == nil {
@@ -1010,7 +1028,7 @@ func (r *walReader) decodeSeries(flag byte, b []byte) ([]RefSeries, error) {
 		}
 		sort.Sort(lset)
 
-		series = append(series, RefSeries{
+		r.seriesBuf = append(r.seriesBuf, RefSeries{
 			Ref:    ref,
 			Labels: lset,
 		})
@@ -1019,16 +1037,16 @@ func (r *walReader) decodeSeries(flag byte, b []byte) ([]RefSeries, error) {
 		return nil, dec.err()
 	}
 	if len(dec.b) > 0 {
-		return series, errors.Errorf("unexpected %d bytes left in entry", len(dec.b))
+		return r.seriesBuf, errors.Errorf("unexpected %d bytes left in entry", len(dec.b))
 	}
-	return series, nil
+	return r.seriesBuf, nil
 }
 
 func (r *walReader) decodeSamples(flag byte, b []byte) ([]RefSample, error) {
 	if len(b) == 0 {
 		return nil, nil
 	}
-	samples := []RefSample{}
+	r.sampleBuf = r.sampleBuf[:0]
 	dec := decbuf{b: b}
 
 	var (
@@ -1041,7 +1059,7 @@ func (r *walReader) decodeSamples(flag byte, b []byte) ([]RefSample, error) {
 		dtime := dec.varint64()
 		val := dec.be64()
 
-		samples = append(samples, RefSample{
+		r.sampleBuf = append(r.sampleBuf, RefSample{
 			Ref: uint64(int64(baseRef) + dref),
 			T:   baseTime + dtime,
 			V:   math.Float64frombits(val),
@@ -1049,20 +1067,20 @@ func (r *walReader) decodeSamples(flag byte, b []byte) ([]RefSample, error) {
 	}
 
 	if dec.err() != nil {
-		return nil, errors.Wrapf(dec.err(), "decode error after %d samples", len(samples))
+		return nil, errors.Wrapf(dec.err(), "decode error after %d samples", len(r.sampleBuf))
 	}
 	if len(dec.b) > 0 {
-		return samples, errors.Errorf("unexpected %d bytes left in entry", len(dec.b))
+		return r.sampleBuf, errors.Errorf("unexpected %d bytes left in entry", len(dec.b))
 	}
-	return samples, nil
+	return r.sampleBuf, nil
 }
 
 func (r *walReader) decodeDeletes(flag byte, b []byte) ([]Stone, error) {
 	dec := &decbuf{b: b}
-	var stones []Stone
+	r.tombstoneBuf = r.tombstoneBuf[:0]
 
 	for dec.len() > 0 && dec.err() == nil {
-		stones = append(stones, Stone{
+		r.tombstoneBuf = append(r.tombstoneBuf, Stone{
 			ref: dec.be64(),
 			intervals: Intervals{
 				{Mint: dec.varint64(), Maxt: dec.varint64()},
@@ -1073,7 +1091,7 @@ func (r *walReader) decodeDeletes(flag byte, b []byte) ([]Stone, error) {
 		return nil, dec.err()
 	}
 	if len(dec.b) > 0 {
-		return stones, errors.Errorf("unexpected %d bytes left in entry", len(dec.b))
+		return r.tombstoneBuf, errors.Errorf("unexpected %d bytes left in entry", len(dec.b))
 	}
-	return stones, nil
+	return r.tombstoneBuf, nil
 }
diff --git a/vendor/vendor.json b/vendor/vendor.json
index bb499c8b4..f5c7a015f 100644
--- a/vendor/vendor.json
+++ b/vendor/vendor.json
@@ -859,22 +859,22 @@
 			"revisionTime": "2016-04-11T19:08:41Z"
 		},
 		{
-			"checksumSHA1": "AoNkGFKIyLNi4a/QcO8p5D7xIXs=",
+			"checksumSHA1": "mDKxPAubVLTWW/Gar13m7YDHSek=",
 			"path": "github.com/prometheus/tsdb",
-			"revision": "0db4c227b72145418ad4c1fbda8fdb87bfe77a02",
-			"revisionTime": "2017-09-07T11:04:02Z"
+			"revision": "3870ec285c4640d462a0ad80e7acbcdf1e939563",
+			"revisionTime": "2017-09-11T08:41:33Z"
 		},
 		{
 			"checksumSHA1": "Gua979gmISm4cJP/fR2hL8m5To8=",
 			"path": "github.com/prometheus/tsdb/chunks",
-			"revision": "0db4c227b72145418ad4c1fbda8fdb87bfe77a02",
-			"revisionTime": "2017-09-07T11:04:02Z"
+			"revision": "3870ec285c4640d462a0ad80e7acbcdf1e939563",
+			"revisionTime": "2017-09-11T08:41:33Z"
 		},
 		{
 			"checksumSHA1": "zhmlvc322RH1L3l9DaA9d/HVVWs=",
 			"path": "github.com/prometheus/tsdb/labels",
-			"revision": "0db4c227b72145418ad4c1fbda8fdb87bfe77a02",
-			"revisionTime": "2017-09-07T11:04:02Z"
+			"revision": "3870ec285c4640d462a0ad80e7acbcdf1e939563",
+			"revisionTime": "2017-09-11T08:41:33Z"
 		},
 		{
 			"checksumSHA1": "5SYLEhADhdBVZAGPVHWggQl7H8k=",