Documentation

Overview

Package metrics implements the Beam metrics API, described at http://s.apache.org/beam-metrics-api

Metrics in the Beam model are uniquely identified by a namespace, a name, and the PTransform context in which they are used. Further, they are reported as a delta against the bundle being processed, so that overcounting doesn't occur if a bundle needs to be retried. Each metric is scoped to their bundle, and ptransform.

Cells (or metric cells) are defined for each Beam model metric type, and the serve as concurrency safe storage of a given metric's values. Proxys are exported values representing the metric, for use in user ptransform code. They don't retain their cells, since they don't have the context to be able to store them for export back to the pipeline runner.

Metric cells aren't initialized until their first mutation, which follows from the Beam model design, where metrics are only sent for a bundle if they have changed. This is particularly convenient for distributions which means their min and max fields can be set to the first value on creation rather than have some marker of uninitialized state, which would otherwise need to be checked for on every update.

Metric values are implemented as lightweight proxies of the user provided namespace and name. This allows them to be declared globally, and used in any ParDo. Further, as per the design, they can be declared dynamically at runtime.

To handle reporting deltas on the metrics by bundle, metrics are keyed by bundleID,PTransformID,namespace, and name, so metrics that are identical except for bundles are treated as distinct, effectively providing per bundle deltas, since a new value cell is used per bundle.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func DumpToLog

func DumpToLog(ctx context.Context)

DumpToLog is a debugging function that outputs all metrics available locally to beam.Log.

func DumpToLogFromStore

func DumpToLogFromStore(ctx context.Context, store *Store)

DumpToLogFromStore dumps the metrics in the provided Store to beam.Log.

func DumpToOutFromContext

func DumpToOutFromContext(ctx context.Context)

DumpToOutFromContext is a debugging function that outputs all metrics available locally to std out, extracting the metric store from the context.

func DumpToOutFromStore

func DumpToOutFromStore(store *Store)

DumpToOutFromStore is a debugging function that outputs all metrics available locally to std out directly from the store.

func SetBundleID

func SetBundleID(ctx context.Context, id string) context.Context

SetBundleID sets the id of the current Bundle, and populates the store.

func SetPTransformID

func SetPTransformID(ctx context.Context, id string) context.Context

SetPTransformID sets the id of the current PTransform. Must only be called on a context returned by SetBundleID.

Types

type Counter

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

Counter is a simple counter for incrementing and decrementing a value.

func NewCounter

func NewCounter(ns, n string) *Counter

NewCounter returns the Counter with the given namespace and name.

func (*Counter) Dec

func (m *Counter) Dec(ctx context.Context, v int64)

Dec decrements the counter within the given PTransform context by v.

func (*Counter) Inc

func (m *Counter) Inc(ctx context.Context, v int64)

Inc increments the counter within the given PTransform context by v.

func (*Counter) String

func (m *Counter) String() string

type Distribution

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

Distribution is a simple distribution of values.

func NewDistribution

func NewDistribution(ns, n string) *Distribution

NewDistribution returns the Distribution with the given namespace and name.

func (*Distribution) String

func (m *Distribution) String() string

func (*Distribution) Update

func (m *Distribution) Update(ctx context.Context, v int64)

Update updates the distribution within the given PTransform context with v.

type Extractor

type Extractor struct {
	// SumInt64 extracts data from Sum Int64 counters.
	SumInt64 func(labels Labels, v int64)
	// DistributionInt64 extracts data from Distribution Int64 counters.
	DistributionInt64 func(labels Labels, count, sum, min, max int64)
	// GaugeInt64 extracts data from Gauge Int64 counters.
	GaugeInt64 func(labels Labels, v int64, t time.Time)
}

Extractor allows users to access metrics programatically after pipeline completion. Users assign functions to fields that interest them, and that function is called for each metric of the associated kind.

func (Extractor) ExtractFrom

func (e Extractor) ExtractFrom(store *Store) error

ExtractFrom the given metrics Store all the metrics for populated function fields. Returns an error if no fields were set.

type Gauge

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

Gauge is a time, value pair metric.

func NewGauge

func NewGauge(ns, n string) *Gauge

NewGauge returns the Gauge with the given namespace and name.

func (*Gauge) Set

func (m *Gauge) Set(ctx context.Context, v int64)

Set sets the gauge to the given value, and associates it with the current time on the clock.

func (*Gauge) String

func (m *Gauge) String() string

type Labels

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

Labels provide the context for the given metric.

func PCollectionLabels

func PCollectionLabels(pcollection string) Labels

PCollectionLabels builds a Labels for pcollection metrics. Intended for framework use.

func PTransformLabels

func PTransformLabels(transform string) Labels

PTransformLabels builds a Labels for transform metrics. Intended for framework use.

func UserLabels

func UserLabels(transform, namespace, name string) Labels

UserLabels builds a Labels for user metrics. Intended for framework use.

func (Labels) Name

func (l Labels) Name() string

Name returns the name for this metric.

func (Labels) Namespace

func (l Labels) Namespace() string

Namespace returns the namespace context for this metric.

func (Labels) Transform

func (l Labels) Transform() string

Transform returns the transform context for this metric, if available.

type Store

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

Store retains per transform countersets, intended for per bundle use.

func GetStore

func GetStore(ctx context.Context) *Store

GetStore extracts the metrics Store for the given context for a bundle.

Returns nil if the context doesn't contain a metric Store.