metrics: Add simple template metrics feature

1 files changed, 117 insertions, 0 deletions

diff --git a/metrics/metrics.go b/metrics/metrics.go
new file mode 100644
index 000000000..cabf52131
--- /dev/null
+++ b/metrics/metrics.go
@@ -0,0 +1,117 @@
+// Copyright 2017 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package metrics provides simple metrics tracking features.
+package metrics
+
+import (
+	"fmt"
+	"io"
+	"sort"
+	"sync"
+	"time"
+)
+
+// The Provider interface defines an interface for measuring metrics.
+type Provider interface {
+	// MeasureSince adds a measurement for key to the metric store.
+	// Used with defer and time.Now().
+	MeasureSince(key string, start time.Time)
+
+	// WriteMetrics will write a summary of the metrics to w.
+	WriteMetrics(w io.Writer)
+
+	// Reset clears the metric store.
+	Reset()
+}
+
+// Store provides storage for a set of metrics.
+type Store struct {
+	metrics map[string][]time.Duration
+	mu      *sync.Mutex
+}
+
+// NewProvider returns a new instance of a metric store.
+func NewProvider() Provider {
+	return &Store{
+		metrics: make(map[string][]time.Duration),
+		mu:      &sync.Mutex{},
+	}
+}
+
+// Reset clears the metrics store.
+func (s *Store) Reset() {
+	s.mu.Lock()
+	s.metrics = make(map[string][]time.Duration)
+	s.mu.Unlock()
+}
+
+// MeasureSince adds a measurement for key to the metric store.
+func (s *Store) MeasureSince(key string, start time.Time) {
+	s.mu.Lock()
+	s.metrics[key] = append(s.metrics[key], time.Since(start))
+	s.mu.Unlock()
+}
+
+// WriteMetrics writes a summary of the metrics to w.
+func (s *Store) WriteMetrics(w io.Writer) {
+	s.mu.Lock()
+
+	results := make([]result, len(s.metrics))
+
+	var i int
+	for k, v := range s.metrics {
+		var sum time.Duration
+		var max time.Duration
+
+		for _, d := range v {
+			sum += d
+			if d > max {
+				max = d
+			}
+		}
+
+		avg := time.Duration(int(sum) / len(v))
+
+		results[i] = result{key: k, count: len(v), max: max, sum: sum, avg: avg}
+		i++
+	}
+
+	s.mu.Unlock()
+
+	// sort and print results
+	fmt.Fprintf(w, "  %13s  %12s  %12s  %5s  %s\n", "cumulative", "average", "maximum", "", "")
+	fmt.Fprintf(w, "  %13s  %12s  %12s  %5s  %s\n", "duration", "duration", "duration", "count", "template")
+	fmt.Fprintf(w, "  %13s  %12s  %12s  %5s  %s\n", "----------", "--------", "--------", "-----", "--------")
+
+	sort.Sort(bySum(results))
+	for _, v := range results {
+		fmt.Fprintf(w, "  %13s  %12s  %12s  %5d  %s\n", v.sum, v.avg, v.max, v.count, v.key)
+	}
+
+}
+
+// A result represents the calculated results for a given metric.
+type result struct {
+	key   string
+	count int
+	sum   time.Duration
+	max   time.Duration
+	avg   time.Duration
+}
+
+type bySum []result
+
+func (b bySum) Len() int           { return len(b) }
+func (b bySum) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+func (b bySum) Less(i, j int) bool { return b[i].sum < b[j].sum }