Make objectives of Summaries explicit

With the next release of client_golang, Summaries will not have
objectives by default.

As it turns out, for prometheus_tsdb_head_gc_duration_seconds and
prometheus_tsdb_wal_truncate_duration_seconds, the objective-less
default makes more sense then the current default.

To make sure we do the right thing before and after the upcoming
release of client_golang, I have set the objectives explicitly
wherever that was not the case so far:

- prometheus_tsdb_head_gc_duration_seconds and
  prometheus_tsdb_wal_truncate_duration_seconds now have no objectives
  explicitly.
- prometheus_tsdb_wal_fsync_duration_seconds now explicitly uses the
  previous default objectives.

Signed-off-by: beorn7 <beorn@grafana.com>

head.go

@@ -141,8 +141,9 @@ func newHeadMetrics(h *Head, r prometheus.Registerer) *headMetrics {
 		Help: "Total number of chunks removed in the head",
 	})
 	m.gcDuration = prometheus.NewSummary(prometheus.SummaryOpts{
-		Name: "prometheus_tsdb_head_gc_duration_seconds",
-		Help: "Runtime of garbage collection in the head block.",
+		Name:       "prometheus_tsdb_head_gc_duration_seconds",
+		Help:       "Runtime of garbage collection in the head block.",
+		Objectives: map[float64]float64{},
 	})
 	m.maxTime = prometheus.NewGaugeFunc(prometheus.GaugeOpts{
 		Name: "prometheus_tsdb_head_max_time",
@@ -157,8 +158,9 @@ func newHeadMetrics(h *Head, r prometheus.Registerer) *headMetrics {
 		return float64(h.MinTime())
 	})
 	m.walTruncateDuration = prometheus.NewSummary(prometheus.SummaryOpts{
-		Name: "prometheus_tsdb_wal_truncate_duration_seconds",
-		Help: "Duration of WAL truncation.",
+		Name:       "prometheus_tsdb_wal_truncate_duration_seconds",
+		Help:       "Duration of WAL truncation.",
+		Objectives: map[float64]float64{},
 	})
 	m.walCorruptionsTotal = prometheus.NewCounter(prometheus.CounterOpts{
 		Name: "prometheus_tsdb_wal_corruptions_total",

wal.go

@@ -65,8 +65,9 @@ func newWalMetrics(wal *SegmentWAL, r prometheus.Registerer) *walMetrics {
 	m := &walMetrics{}
 
 	m.fsyncDuration = prometheus.NewSummary(prometheus.SummaryOpts{
-		Name: "prometheus_tsdb_wal_fsync_duration_seconds",
-		Help: "Duration of WAL fsync.",
+		Name:       "prometheus_tsdb_wal_fsync_duration_seconds",
+		Help:       "Duration of WAL fsync.",
+		Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001},
 	})
 	m.corruptions = prometheus.NewCounter(prometheus.CounterOpts{
 		Name: "prometheus_tsdb_wal_corruptions_total",

wal/wal.go

@@ -200,8 +200,9 @@ func NewSize(logger log.Logger, reg prometheus.Registerer, dir string, segmentSi
 		stopc:       make(chan chan struct{}),
 	}
 	w.fsyncDuration = prometheus.NewSummary(prometheus.SummaryOpts{
-		Name: "prometheus_tsdb_wal_fsync_duration_seconds",
-		Help: "Duration of WAL fsync.",
+		Name:       "prometheus_tsdb_wal_fsync_duration_seconds",
+		Help:       "Duration of WAL fsync.",
+		Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001},
 	})
 	w.pageFlushes = prometheus.NewCounter(prometheus.CounterOpts{
 		Name: "prometheus_tsdb_wal_page_flushes_total",