Improve prometheus plugin

closes #707

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## v0.11.2 [unreleased]
 
 ### Features
+- [#707](https://github.com/influxdata/telegraf/pull/707): Improved prometheus plugin. Thanks @titilambert!
 
 ### Bugfixes
 

plugins/inputs/prometheus/README.md

@@ -0,0 +1,75 @@
+# Prometheus Input Plugin
+
+The prometheus input plugin gathers metrics from any webpage
+exposing metrics with Prometheus format
+
+### Configuration:
+
+Example for Kubernetes apiserver
+```toml
+# Get all metrics from Kube-apiserver
+[[inputs.prometheus]]
+  # An array of urls to scrape metrics from.
+  urls = ["http://my-kube-apiserver:8080/metrics"]
+```
+
+You can use more complex configuration
+to filter and some tags
+
+```toml
+# Get all metrics from Kube-apiserver
+[[inputs.prometheus]]
+  # An array of urls to scrape metrics from.
+  urls = ["http://my-kube-apiserver:8080/metrics"]
+  # Get only metrics with "apiserver_" string is in metric name
+  namepass = ["apiserver_"]
+  # Add a metric name prefix
+  name_prefix = "k8s_"
+  # Add tags to be able to make beautiful dashboards
+  [inputs.prometheus.tags]
+    kubeservice = "kube-apiserver"
+```
+
+### Measurements & Fields & Tags:
+
+Measurements and fields could be any thing.
+It just depends of what you're quering.
+
+Example:
+
+```
+# HELP go_gc_duration_seconds A summary of the GC invocation durations.
+# TYPE go_gc_duration_seconds summary
+go_gc_duration_seconds{quantile="0"} 0.00010425500000000001
+go_gc_duration_seconds{quantile="0.25"} 0.000139108
+go_gc_duration_seconds{quantile="0.5"} 0.00015749400000000002
+go_gc_duration_seconds{quantile="0.75"} 0.000331463
+go_gc_duration_seconds{quantile="1"} 0.000667154
+go_gc_duration_seconds_sum 0.0018183950000000002
+go_gc_duration_seconds_count 7
+# HELP go_goroutines Number of goroutines that currently exist.
+# TYPE go_goroutines gauge
+go_goroutines 15
+```
+
+- go_goroutines,
+    - gauge (integer, unit)
+- go_gc_duration_seconds
+    - field3 (integer, bytes)
+
+- All measurements have the following tags:
+    - url=http://my-kube-apiserver:8080/metrics
+- go_goroutines has the following tags:
+    - kubeservice=kube-apiserver
+- go_gc_duration_seconds has the following tags:
+    - kubeservice=kube-apiserver
+
+### Example Output:
+
+Example of output with configuration given above:
+
+```
+$ ./telegraf -config telegraf.conf  -test
+k8s_go_goroutines,kubeservice=kube-apiserver,url=http://my-kube-apiserver:8080/metrics gauge=536 1456857329391929813
+k8s_go_gc_duration_seconds,kubeservice=kube-apiserver,url=http://my-kube-apiserver:8080/metrics 0=0.038002142,0.25=0.041732467,0.5=0.04336492,0.75=0.047271799,1=0.058295811,count=0,sum=208.334617406 1456857329391929813
+```

plugins/inputs/prometheus/parser.go

@@ -0,0 +1,171 @@
+package prometheus
+
+// Parser inspired from
+// https://github.com/prometheus/prom2json/blob/master/main.go
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"math"
+	"mime"
+
+	"github.com/influxdata/telegraf"
+
+	"github.com/matttproud/golang_protobuf_extensions/pbutil"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
+)
+
+// PrometheusParser is an object for Parsing incoming metrics.
+type PrometheusParser struct {
+	// PromFormat
+	PromFormat map[string]string
+	// DefaultTags will be added to every parsed metric
+	//	DefaultTags map[string]string
+}
+
+// Parse returns a slice of Metrics from a text representation of a
+// metrics
+func (p *PrometheusParser) Parse(buf []byte) ([]telegraf.Metric, error) {
+	var metrics []telegraf.Metric
+	var parser expfmt.TextParser
+	// parse even if the buffer begins with a newline
+	buf = bytes.TrimPrefix(buf, []byte("\n"))
+	// Read raw data
+	buffer := bytes.NewBuffer(buf)
+	reader := bufio.NewReader(buffer)
+
+	// Get format
+	mediatype, params, err := mime.ParseMediaType(p.PromFormat["Content-Type"])
+	// Prepare output
+	metricFamilies := make(map[string]*dto.MetricFamily)
+	if err == nil && mediatype == "application/vnd.google.protobuf" &&
+		params["encoding"] == "delimited" &&
+		params["proto"] == "io.prometheus.client.MetricFamily" {
+		for {
+			metricFamily := &dto.MetricFamily{}
+			if _, err = pbutil.ReadDelimited(reader, metricFamily); err != nil {
+				if err == io.EOF {
+					break
+				}
+				return nil, fmt.Errorf("reading metric family protocol buffer failed: %s", err)
+			}
+			metricFamilies[metricFamily.GetName()] = metricFamily
+		}
+	} else {
+		metricFamilies, err = parser.TextToMetricFamilies(reader)
+		if err != nil {
+			return nil, fmt.Errorf("reading text format failed: %s", err)
+		}
+		// read metrics
+		for metricName, mf := range metricFamilies {
+			for _, m := range mf.Metric {
+				// reading tags
+				tags := makeLabels(m)
+				/*
+					for key, value := range p.DefaultTags {
+						tags[key] = value
+					}
+				*/
+				// reading fields
+				fields := make(map[string]interface{})
+				if mf.GetType() == dto.MetricType_SUMMARY {
+					// summary metric
+					fields = makeQuantiles(m)
+					fields["count"] = float64(m.GetHistogram().GetSampleCount())
+					fields["sum"] = float64(m.GetSummary().GetSampleSum())
+				} else if mf.GetType() == dto.MetricType_HISTOGRAM {
+					// historgram metric
+					fields = makeBuckets(m)
+					fields["count"] = float64(m.GetHistogram().GetSampleCount())
+					fields["sum"] = float64(m.GetSummary().GetSampleSum())
+
+				} else {
+					// standard metric
+					fields = getNameAndValue(m)
+				}
+				// converting to telegraf metric
+				if len(fields) > 0 {
+					metric, err := telegraf.NewMetric(metricName, tags, fields)
+					if err == nil {
+						metrics = append(metrics, metric)
+					}
+				}
+			}
+		}
+	}
+	return metrics, err
+}
+
+// Parse one line
+func (p *PrometheusParser) ParseLine(line string) (telegraf.Metric, error) {
+	metrics, err := p.Parse([]byte(line + "\n"))
+
+	if err != nil {
+		return nil, err
+	}
+
+	if len(metrics) < 1 {
+		return nil, fmt.Errorf(
+			"Can not parse the line: %s, for data format: prometheus", line)
+	}
+
+	return metrics[0], nil
+}
+
+/*
+// Set default tags
+func (p *PrometheusParser) SetDefaultTags(tags map[string]string) {
+	p.DefaultTags = tags
+}
+*/
+
+// Get Quantiles from summary metric
+func makeQuantiles(m *dto.Metric) map[string]interface{} {
+	fields := make(map[string]interface{})
+	for _, q := range m.GetSummary().Quantile {
+		if !math.IsNaN(q.GetValue()) {
+			fields[fmt.Sprint(q.GetQuantile())] = float64(q.GetValue())
+		}
+	}
+	return fields
+}
+
+// Get Buckets  from histogram metric
+func makeBuckets(m *dto.Metric) map[string]interface{} {
+	fields := make(map[string]interface{})
+	for _, b := range m.GetHistogram().Bucket {
+		fields[fmt.Sprint(b.GetUpperBound())] = float64(b.GetCumulativeCount())
+	}
+	return fields
+}
+
+// Get labels from metric
+func makeLabels(m *dto.Metric) map[string]string {
+	result := map[string]string{}
+	for _, lp := range m.Label {
+		result[lp.GetName()] = lp.GetValue()
+	}
+	return result
+}
+
+// Get name and value from metric
+func getNameAndValue(m *dto.Metric) map[string]interface{} {
+	fields := make(map[string]interface{})
+	if m.Gauge != nil {
+		if !math.IsNaN(m.GetGauge().GetValue()) {
+			fields["gauge"] = float64(m.GetGauge().GetValue())
+		}
+	} else if m.Counter != nil {
+		if !math.IsNaN(m.GetGauge().GetValue()) {
+			fields["counter"] = float64(m.GetCounter().GetValue())
+		}
+	} else if m.Untyped != nil {
+		if !math.IsNaN(m.GetGauge().GetValue()) {
+			fields["value"] = float64(m.GetUntyped().GetValue())
+		}
+	}
+	return fields
+}