Update Collector example
It now uses the new WrapWith function instead of ConstLabels. Describe is now implemented via DescribeByCollect. Signed-off-by: beorn7 <beorn@soundcloud.com>
This commit is contained in:
parent
84d7aa0cd9
commit
837c7cb1f4
|
@ -81,6 +81,8 @@ type Collector interface {
|
|||
// it might even get registered as an unchecked Collecter (cf. the Register
|
||||
// method of the Registerer interface). Hence, only use this shortcut
|
||||
// implementation of Describe if you are certain to fulfill the contract.
|
||||
//
|
||||
// The Collector example demonstrates a use of DescribeByCollect.
|
||||
func DescribeByCollect(c Collector, descs chan<- *Desc) {
|
||||
metrics := make(chan Metric)
|
||||
go func() {
|
||||
|
|
|
@ -17,18 +17,18 @@ import "github.com/prometheus/client_golang/prometheus"
|
|||
|
||||
// ClusterManager is an example for a system that might have been built without
|
||||
// Prometheus in mind. It models a central manager of jobs running in a
|
||||
// cluster. To turn it into something that collects Prometheus metrics, we
|
||||
// simply add the two methods required for the Collector interface.
|
||||
// cluster. Thus, we implement a custom Collector called
|
||||
// ClusterManagerCollector, which collects information from a ClusterManager
|
||||
// using its provided methods and turns them into Prometheus Metrics for
|
||||
// collection.
|
||||
//
|
||||
// An additional challenge is that multiple instances of the ClusterManager are
|
||||
// run within the same binary, each in charge of a different zone. We need to
|
||||
// make use of ConstLabels to be able to register each ClusterManager instance
|
||||
// with Prometheus.
|
||||
// make use of wrapping Registerers to be able to register each
|
||||
// ClusterManagerCollector instance with Prometheus.
|
||||
type ClusterManager struct {
|
||||
Zone string
|
||||
OOMCountDesc *prometheus.Desc
|
||||
RAMUsageDesc *prometheus.Desc
|
||||
// ... many more fields
|
||||
Zone string
|
||||
// Contains many more fields not listed in this example.
|
||||
}
|
||||
|
||||
// ReallyExpensiveAssessmentOfTheSystemState is a mock for the data gathering a
|
||||
|
@ -50,10 +50,30 @@ func (c *ClusterManager) ReallyExpensiveAssessmentOfTheSystemState() (
|
|||
return
|
||||
}
|
||||
|
||||
// Describe simply sends the two Descs in the struct to the channel.
|
||||
func (c *ClusterManager) Describe(ch chan<- *prometheus.Desc) {
|
||||
ch <- c.OOMCountDesc
|
||||
ch <- c.RAMUsageDesc
|
||||
// ClusterManagerCollector implements the Collector interface.
|
||||
type ClusterManagerCollector struct {
|
||||
ClusterManager *ClusterManager
|
||||
}
|
||||
|
||||
// Descriptors used by the ClusterManagerCollector below.
|
||||
var (
|
||||
oomCountDesc = prometheus.NewDesc(
|
||||
"clustermanager_oom_crashes_total",
|
||||
"Number of OOM crashes.",
|
||||
[]string{"host"}, nil,
|
||||
)
|
||||
ramUsageDesc = prometheus.NewDesc(
|
||||
"clustermanager_ram_usage_bytes",
|
||||
"RAM usage as reported to the cluster manager.",
|
||||
[]string{"host"}, nil,
|
||||
)
|
||||
)
|
||||
|
||||
// Describe is implemented with DescribeByCollect. That's possible because the
|
||||
// Collect method will always return the same two metrics with the same two
|
||||
// descriptors.
|
||||
func (cc ClusterManagerCollector) Describe(ch chan<- *prometheus.Desc) {
|
||||
prometheus.DescribeByCollect(cc, ch)
|
||||
}
|
||||
|
||||
// Collect first triggers the ReallyExpensiveAssessmentOfTheSystemState. Then it
|
||||
|
@ -61,11 +81,11 @@ func (c *ClusterManager) Describe(ch chan<- *prometheus.Desc) {
|
|||
//
|
||||
// Note that Collect could be called concurrently, so we depend on
|
||||
// ReallyExpensiveAssessmentOfTheSystemState to be concurrency-safe.
|
||||
func (c *ClusterManager) Collect(ch chan<- prometheus.Metric) {
|
||||
oomCountByHost, ramUsageByHost := c.ReallyExpensiveAssessmentOfTheSystemState()
|
||||
func (cc ClusterManagerCollector) Collect(ch chan<- prometheus.Metric) {
|
||||
oomCountByHost, ramUsageByHost := cc.ClusterManager.ReallyExpensiveAssessmentOfTheSystemState()
|
||||
for host, oomCount := range oomCountByHost {
|
||||
ch <- prometheus.MustNewConstMetric(
|
||||
c.OOMCountDesc,
|
||||
oomCountDesc,
|
||||
prometheus.CounterValue,
|
||||
float64(oomCount),
|
||||
host,
|
||||
|
@ -73,7 +93,7 @@ func (c *ClusterManager) Collect(ch chan<- prometheus.Metric) {
|
|||
}
|
||||
for host, ramUsage := range ramUsageByHost {
|
||||
ch <- prometheus.MustNewConstMetric(
|
||||
c.RAMUsageDesc,
|
||||
ramUsageDesc,
|
||||
prometheus.GaugeValue,
|
||||
ramUsage,
|
||||
host,
|
||||
|
@ -81,38 +101,27 @@ func (c *ClusterManager) Collect(ch chan<- prometheus.Metric) {
|
|||
}
|
||||
}
|
||||
|
||||
// NewClusterManager creates the two Descs OOMCountDesc and RAMUsageDesc. Note
|
||||
// that the zone is set as a ConstLabel. (It's different in each instance of the
|
||||
// ClusterManager, but constant over the lifetime of an instance.) Then there is
|
||||
// a variable label "host", since we want to partition the collected metrics by
|
||||
// host. Since all Descs created in this way are consistent across instances,
|
||||
// with a guaranteed distinction by the "zone" label, we can register different
|
||||
// ClusterManager instances with the same registry.
|
||||
func NewClusterManager(zone string) *ClusterManager {
|
||||
return &ClusterManager{
|
||||
// NewClusterManager first creates a Prometheus-ignorant ClusterManager
|
||||
// instance. Then, it creates a ClusterManagerCollector for the just created
|
||||
// ClusterManager. Finally, it registers the ClusterManagerCollector with a
|
||||
// wrapping Registerer that adds the zone as a label. In this way, the metrics
|
||||
// collected by different ClusterManagerCollectors do not collide.
|
||||
func NewClusterManager(zone string, reg prometheus.Registerer) *ClusterManager {
|
||||
c := &ClusterManager{
|
||||
Zone: zone,
|
||||
OOMCountDesc: prometheus.NewDesc(
|
||||
"clustermanager_oom_crashes_total",
|
||||
"Number of OOM crashes.",
|
||||
[]string{"host"},
|
||||
prometheus.Labels{"zone": zone},
|
||||
),
|
||||
RAMUsageDesc: prometheus.NewDesc(
|
||||
"clustermanager_ram_usage_bytes",
|
||||
"RAM usage as reported to the cluster manager.",
|
||||
[]string{"host"},
|
||||
prometheus.Labels{"zone": zone},
|
||||
),
|
||||
}
|
||||
cc := ClusterManagerCollector{ClusterManager: c}
|
||||
prometheus.WrapWith(prometheus.Labels{"zone": zone}, reg).MustRegister(cc)
|
||||
return c
|
||||
}
|
||||
|
||||
func ExampleCollector() {
|
||||
workerDB := NewClusterManager("db")
|
||||
workerCA := NewClusterManager("ca")
|
||||
|
||||
// Since we are dealing with custom Collector implementations, it might
|
||||
// be a good idea to try it out with a pedantic registry.
|
||||
reg := prometheus.NewPedanticRegistry()
|
||||
reg.MustRegister(workerDB)
|
||||
reg.MustRegister(workerCA)
|
||||
|
||||
// Construct cluster managers. In real code, we would assign them to
|
||||
// variables to then do something with them.
|
||||
NewClusterManager("db", reg)
|
||||
NewClusterManager("ca", reg)
|
||||
}
|
||||
|
|
|
@ -30,6 +30,8 @@ import (
|
|||
//
|
||||
// WrapWith provides a way to add fixed labels to a subset of Collectors. It
|
||||
// should not be used to add fixed labels to all metrics exposed.
|
||||
//
|
||||
// The Collector example demonstrates a use of WrapWith.
|
||||
func WrapWith(labels Labels, reg Registerer) Registerer {
|
||||
return &wrappingRegisterer{
|
||||
wrappedRegisterer: reg,
|
||||
|
|
Loading…
Reference in New Issue