metric

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 Go to latest Published: Sep 20, 2016 License: Apache-2.0 Imports: 16 Imported by: 0

Documentation

Overview

Package metric provides server metrics (a.k.a. transient stats) for a CockroachDB server. These metrics are persisted to the time-series database and are viewable through the web interface and the /_status/metrics/<NODEID> HTTP endpoint.

Adding a new metric

First, add the metric to a Registry.

Next, call methods such as Counter() and Rate() on the Registry to register the metric. For example: 

exec := &Executor{
	...
	selectCount: sqlRegistry.Counter("sql.select.count"),
	...
}

This code block registers the metric "sql.select.count" in sql.Registry. The metric can then be accessed through the "selectCount" variable, which can be updated as follows: 

func (e *Executor) doSelect() {
	// do the SELECT
	e.selectCount.Inc(1)
}

To add the metric to the web UI, modify the appropriate file in "ui/ts/pages/*.ts". Someone more qualified than me can elaborate, like @maxlang.

Sub-registries

It's common for a Registry to become part of another Registry through the "Add" and "MustAdd" methods. 

func NewNodeStatusMonitor(serverRegistry *registry) {
	nodeRegistry := metric.NewRegistry()

	// Add the registry for this node to the root-level server Registry. When
	// accessed from through the serverRegistry, all metrics from the
	// nodeRegistry will have the prefix "cr.node.".
	serverRegistry.MustAdd("cr.node.%s", nodeRegistry)
}

Node-level sub-registries are added by calling: 

(*metric.MetricRecorder).AddNodeRegistry(YOUR_NODE_SUBREGISTRY)

Testing

After your test does something to trigger your new metric update, you'll probably want to call methods in TestServer such as MustGetSQLCounter() to verify that the metric was updated correctly. See "sql/metric_test.go" for an example.

Additionally, you can manually verify that your metric is updating by using the metrics endpoint. For example, if you're running the Cockroach DB server with the "--insecure" flag, you can use access the endpoint as follows: 

$ curl http://localhost:8080/_status/nodes/1

(some other output)
"cr.node.sql.select.count.1": 5,
(some other output)

Note that a prefix and suffix have been added. The prefix "cr.node." denotes that this metric is node-level. The suffix ".1" specifies that this metric is for node 1.

Index

Constants

This section is empty.

Variables

View Source 
var (
	// Scale1M is a 1 minute window for windowed stats (e.g. Rates and Histograms).
	Scale1M = TimeScale{"1m", 1 * time.Minute}

	// Scale10M is a 10 minute window for windowed stats (e.g. Rates and Histograms).
	Scale10M = TimeScale{"10m", 10 * time.Minute}

	// Scale1H is a 1 hour window for windowed stats (e.g. Rates and Histograms).
	Scale1H = TimeScale{"1h", time.Hour}
)
View Source 
var DefaultTimeScales = []TimeScale{Scale1M, Scale10M, Scale1H}

DefaultTimeScales are the durations used for helpers which create windowed metrics in bulk (such as Latency or Rates).

Functions

func TestingSetNow 

func TestingSetNow(f func() time.Time) func()

TestingSetNow changes the clock used by the metric system. For use by testing to precisely control the clock.

Types

type Counter 

type Counter struct {
	Metadata
	metrics.Counter
}

A Counter holds a single mutable atomic value.

func NewCounter 

func NewCounter(metadata Metadata) *Counter

NewCounter creates a counter.

func (*Counter) GetType 

func (c *Counter) GetType() *prometheusgo.MetricType

GetType returns the prometheus type enum for this metric.

func (*Counter) Inspect 

func (c *Counter) Inspect(f func(interface{}))

Inspect calls the given closure with the empty string and itself.

func (*Counter) MarshalJSON 

func (c *Counter) MarshalJSON() ([]byte, error)

MarshalJSON marshals to JSON.

func (*Counter) ToPrometheusMetric 

func (c *Counter) ToPrometheusMetric() *prometheusgo.Metric

ToPrometheusMetric returns a filled-in prometheus metric of the right type.

type Gauge 

type Gauge struct {
	Metadata
	metrics.Gauge
}

A Gauge atomically stores a single integer value.

func NewGauge 

func NewGauge(metadata Metadata) *Gauge

NewGauge creates a Gauge.

func (*Gauge) GetType 

func (g *Gauge) GetType() *prometheusgo.MetricType

GetType returns the prometheus type enum for this metric.

func (*Gauge) Inspect 

func (g *Gauge) Inspect(f func(interface{}))

Inspect calls the given closure with the empty string and itself.

func (*Gauge) MarshalJSON 

func (g *Gauge) MarshalJSON() ([]byte, error)

MarshalJSON marshals to JSON.

func (*Gauge) ToPrometheusMetric 

func (g *Gauge) ToPrometheusMetric() *prometheusgo.Metric

ToPrometheusMetric returns a filled-in prometheus metric of the right type.

type GaugeFloat64 

type GaugeFloat64 struct {
	Metadata
	metrics.GaugeFloat64
}

A GaugeFloat64 atomically stores a single float64 value.

func NewGaugeFloat64 

func NewGaugeFloat64(metadata Metadata) *GaugeFloat64

NewGaugeFloat64 creates a GaugeFloat64.

func (*GaugeFloat64) GetType 

func (g *GaugeFloat64) GetType() *prometheusgo.MetricType

GetType returns the prometheus type enum for this metric.

func (*GaugeFloat64) Inspect 

func (g *GaugeFloat64) Inspect(f func(interface{}))

Inspect calls the given closure with the empty string and itself.

func (*GaugeFloat64) MarshalJSON 

func (g *GaugeFloat64) MarshalJSON() ([]byte, error)

MarshalJSON marshals to JSON.

func (*GaugeFloat64) ToPrometheusMetric 

func (g *GaugeFloat64) ToPrometheusMetric() *prometheusgo.Metric

ToPrometheusMetric returns a filled-in prometheus metric of the right type.

type Histogram 

type Histogram struct {
	Metadata
	// contains filtered or unexported fields
}

A Histogram is a wrapper around an hdrhistogram.WindowedHistogram.

func NewHistogram 

func NewHistogram(metadata Metadata, duration time.Duration,
	maxVal int64, sigFigs int) *Histogram

NewHistogram creates a new windowed HDRHistogram with the given parameters. Data is kept in the active window for approximately the given duration. See the documentation for hdrhistogram.WindowedHistogram for details.

func (*Histogram) Current 

func (h *Histogram) Current() *hdrhistogram.Histogram

Current returns a copy of the data currently in the window.

func (*Histogram) GetType 

func (h *Histogram) GetType() *prometheusgo.MetricType

GetType returns the prometheus type enum for this metric.

func (*Histogram) Inspect 

func (h *Histogram) Inspect(f func(interface{}))

Inspect calls the closure with the empty string and the receiver.

func (*Histogram) MarshalJSON 

func (h *Histogram) MarshalJSON() ([]byte, error)

MarshalJSON outputs to JSON.

func (*Histogram) RecordValue 

func (h *Histogram) RecordValue(v int64)

RecordValue adds the given value to the histogram, truncating if necessary.

func (*Histogram) ToPrometheusMetric 

func (h *Histogram) ToPrometheusMetric() *prometheusgo.Metric

ToPrometheusMetric returns a filled-in prometheus metric of the right type.

type Histograms 

type Histograms map[TimeScale]*Histogram

Histograms is a map of Histogram metrics.

func NewLatency 

func NewLatency(metadata Metadata) Histograms

NewLatency is a convenience function which registers histograms with suitable defaults for latency tracking. Values are expressed in ns, are truncated into the interval [0, time.Minute] and are recorded with two digits of precision (i.e. errors of <1ms at 100ms, <.6s at 1m). The generated names of the metric will begin with the given prefix.

TODO(mrtracy,tschottdorf): need to discuss roll-ups and generally how (and which) information flows between metrics and time series.

func (Histograms) RecordValue 

func (hs Histograms) RecordValue(v int64)

RecordValue calls through to each individual Histogram.

type Iterable 

type Iterable interface {
	// GetName returns the fully-qualified name of the metric.
	GetName() string
	// GetHelp returns the help text for the metric.
	GetHelp() string
	// Inspect calls the given closure with each contained item.
	Inspect(func(interface{}))
}

Iterable provides a method for synchronized access to interior objects.

type Metadata 

type Metadata struct {
	Name, Help string
	// contains filtered or unexported fields
}

Metadata holds metadata about a metric. It must be embedded in each metric object.

func (*Metadata) AddLabel 

func (m *Metadata) AddLabel(name, value string)

AddLabel adds a label/value pair for this metric.

func (*Metadata) GetHelp 

func (m *Metadata) GetHelp() string

GetHelp returns the metric's help string.

func (*Metadata) GetLabels 

func (m *Metadata) GetLabels() []*prometheusgo.LabelPair

GetLabels returns the metric's labels.

func (*Metadata) GetName 

func (m *Metadata) GetName() string

GetName returns the metric's name.

type PrometheusExportable 

type PrometheusExportable interface {
	// GetName is a method on Metadata
	GetName() string
	// GetHelp is a method on Metadata
	GetHelp() string
	// GetType returns the prometheus type enum for this metric.
	GetType() *prometheusgo.MetricType
	// GetLabels is a method on Metadata
	GetLabels() []*prometheusgo.LabelPair
	// ToPrometheusMetric returns a filled-in prometheus metric of the right type
	// for the given metric. It does not fill in labels.
	ToPrometheusMetric() *prometheusgo.Metric
}

PrometheusExportable is the standard interface for an individual metric that can be exported to prometheus.

type PrometheusExporter 

type PrometheusExporter struct {
	// contains filtered or unexported fields
}

PrometheusExporter contains a map of metric families (a metric with multiple labels). It initializes each metric family once and reuses it for each prometheus scrape. It is NOT thread-safe. TODO(marc): we should really keep out metric objects here so we can avoid creating new prometheus.Metric every time we are scraped. see: https://github.com/cockroachdb/cockroach/issues/9326 

pe := MakePrometheusExporter()
pe.AddMetricsFromRegistry(nodeRegistry)
pe.AddMetricsFromRegistry(storeOneRegistry)
...
pe.AddMetricsFromRegistry(storeNRegistry)
pe.Export(w)

func MakePrometheusExporter 

func MakePrometheusExporter() PrometheusExporter

MakePrometheusExporter returns an initialized prometheus exporter.

func (*PrometheusExporter) AddMetricsFromRegistry 

func (pm *PrometheusExporter) AddMetricsFromRegistry(registry *Registry)

AddMetricsFromRegistry takes a registry and adds all metrics to the metric family map. It creates a new family if needed.

func (*PrometheusExporter) Export 

func (pm *PrometheusExporter) Export(w io.Writer) error

Export writes all metrics in the families map to the iowriter in prometheus' text format. It removes individual metrics from the families as it goes, readying the families for another found of registry additions.

type Rate 

type Rate struct {
	Metadata
	// contains filtered or unexported fields
}

A Rate is a exponential weighted moving average.

func NewRate 

func NewRate(metadata Metadata, timescale time.Duration) *Rate

NewRate creates an EWMA rate on the given timescale. Timescales at or below 2s are illegal and will cause a panic.

func (*Rate) Add 

func (e *Rate) Add(v float64)

Add adds the given measurement to the Rate.

func (*Rate) Inspect 

func (e *Rate) Inspect(f func(interface{}))

Inspect calls the given closure with the empty string and the Rate's current value. TODO(mrtracy): Fix this to pass the Rate object itself to 'f', to match the 'visitor' behavior as the other metric types (currently, it passes the current value of the Rate as a float64.)

func (*Rate) MarshalJSON 

func (e *Rate) MarshalJSON() ([]byte, error)

MarshalJSON marshals to JSON.

func (*Rate) Value 

func (e *Rate) Value() float64

Value returns the current value of the Rate.

type Rates 

type Rates struct {
	*Counter
	Rates map[TimeScale]*Rate
}

Rates is a counter and associated EWMA backed rates at different time scales.

func NewRates 

func NewRates(metadata Metadata) Rates

NewRates registers and returns a new Rates instance, which contains a set of EWMA-based rates with generally useful time scales and a cumulative counter.

func (Rates) Add 

func (es Rates) Add(v int64)

Add adds the given value to all contained objects.

type Registry 

type Registry struct {
	syncutil.Mutex
	// contains filtered or unexported fields
}

A Registry is a list of metrics. It provides a simple way of iterating over them, can marshal into JSON, and generate a prometheus format.

A registry can have label pairs that will be applied to all its metrics when exported to prometheus.

func NewRegistry 

func NewRegistry() *Registry

NewRegistry creates a new Registry.

func (*Registry) AddLabel 

func (r *Registry) AddLabel(name, value string)

AddLabel adds a label/value pair for this registry.

func (*Registry) AddMetric 

func (r *Registry) AddMetric(metric Iterable)

AddMetric adds the passed-in metric to the registry.

func (*Registry) AddMetricGroup 

func (r *Registry) AddMetricGroup(group metricGroup)

AddMetricGroup expands the metric group and adds all of them as individual metrics to the registry.

func (*Registry) AddMetricStruct 

func (r *Registry) AddMetricStruct(metricStruct interface{})

AddMetricStruct examines all fields of metricStruct and adds all Iterable or metricGroup objects to the registry.

func (*Registry) Each 

func (r *Registry) Each(f func(name string, val interface{}))

Each calls the given closure for all metrics.

func (*Registry) MarshalJSON 

func (r *Registry) MarshalJSON() ([]byte, error)

MarshalJSON marshals to JSON.

type TimeScale 

type TimeScale struct {
	// contains filtered or unexported fields
}

A TimeScale is a named duration.

func (TimeScale) Name 

func (ts TimeScale) Name() string

Name returns the name of the TimeScale.

Source Files

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