client_golang/prometheus/examples_test.go

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// Copyright 2014 Prometheus Team
// 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 prometheus_test
import (
"flag"
"fmt"
"math"
"net/http"
"runtime"
"sort"
dto "github.com/prometheus/client_model/go"
"code.google.com/p/goprotobuf/proto"
"github.com/prometheus/client_golang/prometheus"
)
func ExampleGauge() {
opsQueued := prometheus.NewGauge(prometheus.GaugeOpts{
Namespace: "our_company",
Subsystem: "blob_storage",
Name: "ops_queued",
Help: "Number of blob storage operations waiting to be processed.",
})
prometheus.MustRegister(opsQueued)
// 10 operations queued by the goroutine managing incoming requests.
opsQueued.Add(10)
// A worker goroutine has picked up a waiting operation.
opsQueued.Dec()
// And once more...
opsQueued.Dec()
}
func ExampleGaugeVec() {
binaryVersion := flag.String("binary_version", "debug", "Version of the binary: debug, canary, production.")
flag.Parse()
opsQueued := prometheus.NewGaugeVec(
prometheus.GaugeOpts{
Namespace: "our_company",
Subsystem: "blob_storage",
Name: "ops_queued",
Help: "Number of blob storage operations waiting to be processed, partitioned by user and type.",
ConstLabels: prometheus.Labels{"binary_version": *binaryVersion},
},
[]string{
// Which user has requested the operation?
"user",
// Of what type is the operation?
"type",
},
)
prometheus.MustRegister(opsQueued)
// Increase a value using compact (but order-sensitive!) WithLabelValues().
opsQueued.WithLabelValues("bob", "put").Add(4)
// Increase a value with a map using WithLabels. More verbose, but order
// doesn't matter anymore.
opsQueued.With(prometheus.Labels{"type": "delete", "user": "alice"}).Inc()
}
func ExampleGaugeFunc() {
if _, err := prometheus.Register(prometheus.NewGaugeFunc(
prometheus.GaugeOpts{
Subsystem: "runtime",
Name: "goroutines_count",
Help: "Number of goroutines that currently exist.",
},
func() float64 { return float64(runtime.NumGoroutine()) },
)); err == nil {
fmt.Println("GaugeFunc 'goroutines_count' registered.")
}
// Note that the count of goroutines is a gauge (and not a counter) as
// it can go up and down.
// Output:
// GaugeFunc 'goroutines_count' registered.
}
func ExampleCounter() {
pushCounter := prometheus.NewCounter(prometheus.CounterOpts{
Name: "repository_pushes", // Note: No help string...
})
_, err := prometheus.Register(pushCounter) // ... so this will return an error.
if err != nil {
fmt.Println("Push counter couldn't be registered, no counting will happen:", err)
return
}
// Try it once more, this time with a help string.
pushCounter = prometheus.NewCounter(prometheus.CounterOpts{
Name: "repository_pushes",
Help: "Number of pushes to external repository.",
})
_, err = prometheus.Register(pushCounter)
if err != nil {
fmt.Println("Push counter couldn't be registered AGAIN, no counting will happen:", err)
return
}
pushComplete := make(chan struct{})
// TODO: Start a goroutine that performs repository pushes and reports
// each completion via the channel.
for _ = range pushComplete {
pushCounter.Inc()
}
// Output:
// Push counter couldn't be registered, no counting will happen: descriptor Desc{fqName: "repository_pushes", help: "", constLabels: {}, variableLabels: []} is invalid: empty help string
}
func ExampleCounterVec() {
binaryVersion := flag.String("environment", "test", "Execution environment: test, staging, production.")
flag.Parse()
httpReqs := prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "http_requests_total",
Help: "How many HTTP requests processed, partitioned by status code and http method.",
ConstLabels: prometheus.Labels{"env": *binaryVersion},
},
[]string{"code", "method"},
)
prometheus.MustRegister(httpReqs)
httpReqs.WithLabelValues("404", "POST").Add(42)
// If you have to access the same set of labels very frequently, it
// might be good to retrieve the metric only once and keep a handle to
// it. But beware of deletion of that metric, see below!
m := httpReqs.WithLabelValues("200", "GET")
for i := 0; i < 1000000; i++ {
m.Inc()
}
// Delete a metric from the vector. If you have previously kept a handle
// to that metric (as above), future updates via that handle will go
// unseen (even if you re-create a metric with the same label set
// later).
httpReqs.DeleteLabelValues("200", "GET")
// Same thing with the more verbose Labels syntax.
httpReqs.Delete(prometheus.Labels{"method": "GET", "code": "200"})
}
func ExampleInstrumentHandler() {
// Handle the "/doc" endpoint with the standard http.FileServer handler.
// By wrapping the handler with InstrumentHandler, request count,
// request and response sizes, and request latency are automatically
// exported to Prometheus, partitioned by HTTP status code and method
// and by the handler name (here "fileserver").
http.Handle("/doc", prometheus.InstrumentHandler(
"fileserver", http.FileServer(http.Dir("/usr/share/doc")),
))
// The Prometheus handler still has to be registered to handle the
// "/metrics" endpoint. The handler returned by prometheus.Handler() is
// already instrumented - with "prometheus" as the handler name. In this
// example, we want the handler name to be "metrics", so we instrument
// the uninstrumented Prometheus handler ourselves.
http.Handle("/metrics", prometheus.InstrumentHandler(
"metrics", prometheus.UninstrumentedHandler(),
))
}
func ExampleLabelPairSorter() {
labelPairs := []*dto.LabelPair{
&dto.LabelPair{Name: proto.String("status"), Value: proto.String("404")},
&dto.LabelPair{Name: proto.String("method"), Value: proto.String("get")},
}
sort.Sort(prometheus.LabelPairSorter(labelPairs))
fmt.Println(labelPairs)
// Output:
// [name:"method" value:"get" name:"status" value:"404" ]
}
func ExampleRegister() {
// Imagine you have a worker pool and want to count the tasks completed.
taskCounter := prometheus.NewCounter(prometheus.CounterOpts{
Subsystem: "worker_pool",
Name: "completed_tasks_total",
Help: "Total number of tasks completed.",
})
// This will register fine.
if _, err := prometheus.Register(taskCounter); err != nil {
fmt.Println(err)
} else {
fmt.Println("taskCounter registered.")
}
// Don't forget to tell the HTTP server about the Prometheus handler.
// (In a real program, you still need to start the http server...)
http.Handle("/metrics", prometheus.Handler())
// Now you can start workers and give every one of them a pointer to
// taskCounter and let it increment it whenever it completes a task.
taskCounter.Inc() // This has to happen somewhere in the worker code.
// But wait, you want to see how individual workers perform. So you need
// a vector of counters, with one element for each worker.
taskCounterVec := prometheus.NewCounterVec(
prometheus.CounterOpts{
Subsystem: "worker_pool",
Name: "completed_tasks_total",
Help: "Total number of tasks completed.",
},
[]string{"worker_id"},
)
// Registering will fail because we already have a metric of that name.
if _, err := prometheus.Register(taskCounterVec); err != nil {
fmt.Println("taskCounterVec not registered:", err)
} else {
fmt.Println("taskCounterVec registered.")
}
// To fix, first unregister the old taskCounter.
if prometheus.Unregister(taskCounter) {
fmt.Println("taskCounter unregistered.")
}
// Try registering taskCounterVec again.
if _, err := prometheus.Register(taskCounterVec); err != nil {
fmt.Println("taskCounterVec not registered:", err)
} else {
fmt.Println("taskCounterVec registered.")
}
// Bummer! Still doesn't work.
// Prometheus will not allow you to ever export metrics with
// inconsistent help strings or label names. After unregistering, the
// unregistered metrics will cease to show up in the /metrics http
// response, but the registry still remembers that those metrics had
// been exported before. For this example, we will now choose a
// different name. (In a real program, you would obviously not export
// the obsolete metric in the first place.)
taskCounterVec = prometheus.NewCounterVec(
prometheus.CounterOpts{
Subsystem: "worker_pool",
Name: "completed_tasks_by_id",
Help: "Total number of tasks completed.",
},
[]string{"worker_id"},
)
if _, err := prometheus.Register(taskCounterVec); err != nil {
fmt.Println("taskCounterVec not registered:", err)
} else {
fmt.Println("taskCounterVec registered.")
}
// Finally it worked!
// The workers have to tell taskCounterVec their id to increment the
// right element in the metric vector.
taskCounterVec.WithLabelValues("42").Inc() // Code from worker 42.
// Each worker could also keep a reference to their own counter element
// around. Pick the counter at initialization time of the worker.
myCounter := taskCounterVec.WithLabelValues("42") // From worker 42 initialization code.
myCounter.Inc() // Somewhere in the code of that worker.
// Note that something like WithLabelValues("42", "spurious arg") would
// panic (because you have provided too many label values). If you want
// to get an error instead, use GetMetricWithLabelValues(...) instead.
notMyCounter, err := taskCounterVec.GetMetricWithLabelValues("42", "spurious arg")
if err != nil {
fmt.Println("Worker initialization failed:", err)
}
if notMyCounter == nil {
fmt.Println("notMyCounter is nil.")
}
// A different (and somewhat tricky) approach is to use
// ConstLabels. ConstLabels are pairs of label names and label values
// that never change. You might ask what those labels are good for (and
// rightfully so - if they never change, they could as well be part of
// the metric name). There are essentially two use-cases: The first is
// if labels are constant throughout the lifetime of a binary execution,
// but they vary over time or between different instances of a running
// binary. The second is what we have here: Each worker creates and
// registers an own Counter instance where the only difference is in the
// value of the ConstLabels. Those Counters can all be registered
// because the different ConstLabel values guarantee that each worker
// will increment a different Counter metric.
counterOpts := prometheus.CounterOpts{
Subsystem: "worker_pool",
Name: "completed_tasks",
Help: "Total number of tasks completed.",
ConstLabels: prometheus.Labels{"worker_id": "42"},
}
taskCounterForWorker42 := prometheus.NewCounter(counterOpts)
if _, err := prometheus.Register(taskCounterForWorker42); err != nil {
fmt.Println("taskCounterVForWorker42 not registered:", err)
} else {
fmt.Println("taskCounterForWorker42 registered.")
}
// Obviously, in real code, taskCounterForWorker42 would be a member
// variable of a worker struct, and the "42" would be retrieved with a
// GetId() method or something. The Counter would be created and
// registered in the initialization code of the worker.
// For the creation of the next Counter, we can recycle
// counterOpts. Just change the ConstLabels.
counterOpts.ConstLabels = prometheus.Labels{"worker_id": "2001"}
taskCounterForWorker2001 := prometheus.NewCounter(counterOpts)
if _, err := prometheus.Register(taskCounterForWorker2001); err != nil {
fmt.Println("taskCounterVForWorker2001 not registered:", err)
} else {
fmt.Println("taskCounterForWorker2001 registered.")
}
taskCounterForWorker2001.Inc()
taskCounterForWorker42.Inc()
taskCounterForWorker2001.Inc()
// Yet another approach would be to turn the workers themselves into
// Collectors and register them. See the Collector example for details.
// Output:
// taskCounter registered.
// taskCounterVec not registered: a previously registered descriptor with the same fully-qualified name as Desc{fqName: "worker_pool_completed_tasks_total", help: "Total number of tasks completed.", constLabels: {}, variableLabels: [worker_id]} has different label names or a different help string
// taskCounter unregistered.
// taskCounterVec not registered: a previously registered descriptor with the same fully-qualified name as Desc{fqName: "worker_pool_completed_tasks_total", help: "Total number of tasks completed.", constLabels: {}, variableLabels: [worker_id]} has different label names or a different help string
// taskCounterVec registered.
// Worker initialization failed: inconsistent label cardinality
// notMyCounter is nil.
// taskCounterForWorker42 registered.
// taskCounterForWorker2001 registered.
}
func ExampleSummary() {
temps := prometheus.NewSummary(prometheus.SummaryOpts{
Name: "pond_temperature_celsius",
Help: "The temperature of the frog pond.", // Sorry, we can't measure how badly it smells.
})
// Simulate some observations.
for i := 0; i < 1000; i++ {
temps.Observe(30 + math.Floor(120*math.Sin(float64(i)*0.1))/10)
}
// Just for demonstration, let's check the state of the summary by
// (ab)using its Write method (which is usually only used by Prometheus
// internally).
metric := &dto.Metric{}
temps.Write(metric)
fmt.Println(proto.MarshalTextString(metric))
// Output:
// summary: <
// sample_count: 1000
// sample_sum: 29969.50000000001
// quantile: <
// quantile: 0.5
// value: 30.2
// >
// quantile: <
// quantile: 0.9
// value: 41.4
// >
// quantile: <
// quantile: 0.99
// value: 41.9
// >
// >
}
func ExampleSummaryVec() {
temps := prometheus.NewSummaryVec(
prometheus.SummaryOpts{
Name: "pond_temperature_celsius",
Help: "The temperature of the frog pond.", // Sorry, we can't measure how badly it smells.
},
[]string{"species"},
)
// Simulate some observations.
for i := 0; i < 1000; i++ {
temps.WithLabelValues("litoria-caerulea").Observe(30 + math.Floor(120*math.Sin(float64(i)*0.1))/10)
temps.WithLabelValues("lithobates-catesbeianus").Observe(32 + math.Floor(100*math.Cos(float64(i)*0.11))/10)
}
// Just for demonstration, let's check the state of the summary vector
// by (ab)using its Collect method and the Write method of its elements
// (which is usually only used by Prometheus internally - code like the
// following will never appear in your own code).
metricChan := make(chan prometheus.Metric)
go func() {
defer close(metricChan)
temps.Collect(metricChan)
}()
metricStrings := []string{}
for metric := range metricChan {
dtoMetric := &dto.Metric{}
metric.Write(dtoMetric)
metricStrings = append(metricStrings, proto.MarshalTextString(dtoMetric))
}
sort.Strings(metricStrings) // For reproducible print order.
fmt.Println(metricStrings)
// Output:
// [label: <
// name: "species"
// value: "lithobates-catesbeianus"
// >
// summary: <
// sample_count: 1000
// sample_sum: 31956.100000000017
// quantile: <
// quantile: 0.5
// value: 32
// >
// quantile: <
// quantile: 0.9
// value: 41.5
// >
// quantile: <
// quantile: 0.99
// value: 41.9
// >
// >
// label: <
// name: "species"
// value: "litoria-caerulea"
// >
// summary: <
// sample_count: 1000
// sample_sum: 29969.50000000001
// quantile: <
// quantile: 0.5
// value: 30.2
// >
// quantile: <
// quantile: 0.9
// value: 41.4
// >
// quantile: <
// quantile: 0.99
// value: 41.9
// >
// >
// ]
}