前言
Prometheus 提供了官方版 Golang 库(https://github.com/prometheus/client_golang) 用于采集并暴露监控数据，本文快速为你介绍如何使用官方版 Golang 库来暴露 Golang runtime 相关的数据，以及其它一些基本简单的示例，并使用 Prometheus 监控服务来采集指标展示数据。
❝
有关全面的 API 文档，请参见 Prometheus 的各种 Go 库的 GoDoc (https://godoc.org/github.com/prometheus/client_golang)文档。
❞
安装
通过 go get 命令来安装相关依赖库，示例如下：
go get github.com/prometheus/client_golang/prometheus
go get github.com/prometheus/client_golang/prometheus/promauto
go get github.com/prometheus/client_golang/prometheus/promhttp安装所需的 prometheus, promauto 和 promhttp 库。
$ time go get github.com/prometheus/client_golang/prometheus
real 0m2.054s
user 0m0.000s
sys 0m0.015s
$ time go get github.com/prometheus/client_golang/prometheus/promauto
real 0m4.368s
user 0m0.000s
sys 0m0.015s
$ time go get github.com/prometheus/client_golang/prometheus/promhttp
real 0m3.109s
user 0m0.000s
sys 0m0.047s快速开始（运行时指标）
准备一个 HTTP 服务，路径通常使用 /metrics。可以直接使用 prometheus/promhttp 里提供的 Handler 函数。如下是一个简单的示例应用，通过 http://localhost:2112/metrics 暴露 Golang 应用的一些默认指标数据（包括运行时指标、进程相关指标以及构建相关的指标）：
package main
import (
"net/http"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
func main() {
//提供 /metrics HTTP 端点
http.Handle("/metrics", promhttp.Handler())
//端口号
http.ListenAndServe(":2112", nil)
}执行以下命令启动应用：
go run main.go执行以下命令，访问基础内置指标数据：
curl http://localhost:2112/metrics# HELP go_gc_duration_seconds A summary of the pause duration of garbage collection cycles.
# TYPE go_gc_duration_seconds summary
go_gc_duration_seconds{quantile="0"} 0
go_gc_duration_seconds{quantile="0.25"} 0
go_gc_duration_seconds{quantile="0.5"} 0
go_gc_duration_seconds{quantile="0.75"} 0
go_gc_duration_seconds{quantile="1"} 0
go_gc_duration_seconds_sum 0
go_gc_duration_seconds_count 0
# HELP go_goroutines Number of goroutines that currently exist.
# TYPE go_goroutines gauge
go_goroutines 7
# HELP go_info Information about the Go environment.
# TYPE go_info gauge
go_info{version="go1.16.7"} 1
# HELP go_memstats_alloc_bytes Number of bytes allocated and still in use.
# TYPE go_memstats_alloc_bytes gauge
go_memstats_alloc_bytes 611920
# HELP go_memstats_alloc_bytes_total Total number of bytes allocated, even if freed.
# TYPE go_memstats_alloc_bytes_total counter
go_memstats_alloc_bytes_total 611920
# HELP go_memstats_buck_hash_sys_bytes Number of bytes used by the profiling bucket hash table.
# TYPE go_memstats_buck_hash_sys_bytes gauge
go_memstats_buck_hash_sys_bytes 4081
# HELP go_memstats_frees_total Total number of frees.
# TYPE go_memstats_frees_total counter
go_memstats_frees_total 112
# HELP go_memstats_gc_cpu_fraction The fraction of this program's available CPU time used by the GC since the program started.
# TYPE go_memstats_gc_cpu_fraction gauge
go_memstats_gc_cpu_fraction 0
# HELP go_memstats_gc_sys_bytes Number of bytes used for garbage collection system metadata.
# TYPE go_memstats_gc_sys_bytes gauge
go_memstats_gc_sys_bytes 3.962144e+06
# HELP go_memstats_heap_alloc_bytes Number of heap bytes allocated and still in use.
# TYPE go_memstats_heap_alloc_bytes gauge
go_memstats_heap_alloc_bytes 611920
# HELP go_memstats_heap_idle_bytes Number of heap bytes waiting to be used.
# TYPE go_memstats_heap_idle_bytes gauge
go_memstats_heap_idle_bytes 6.5273856e+07
# HELP go_memstats_heap_inuse_bytes Number of heap bytes that are in use.
# TYPE go_memstats_heap_inuse_bytes gauge
go_memstats_heap_inuse_bytes 1.47456e+06
# HELP go_memstats_heap_objects Number of allocated objects.
# TYPE go_memstats_heap_objects gauge
go_memstats_heap_objects 2296
# HELP go_memstats_heap_released_bytes Number of heap bytes released to OS.
# TYPE go_memstats_heap_released_bytes gauge
go_memstats_heap_released_bytes 6.5273856e+07
# HELP go_memstats_heap_sys_bytes Number of heap bytes obtained from system.
# TYPE go_memstats_heap_sys_bytes gauge
go_memstats_heap_sys_bytes 6.6748416e+07
# HELP go_memstats_last_gc_time_seconds Number of seconds since 1970 of last garbage collection.
# TYPE go_memstats_last_gc_time_seconds gauge
go_memstats_last_gc_time_seconds 0
# HELP go_memstats_lookups_total Total number of pointer lookups.
# TYPE go_memstats_lookups_total counter
go_memstats_lookups_total 0
# HELP go_memstats_mallocs_total Total number of mallocs.
# TYPE go_memstats_mallocs_total counter
go_memstats_mallocs_total 2408
# HELP go_memstats_mcache_inuse_bytes Number of bytes in use by mcache structures.
# TYPE go_memstats_mcache_inuse_bytes gauge
go_memstats_mcache_inuse_bytes 14400
# HELP go_memstats_mcache_sys_bytes Number of bytes used for mcache structures obtained from system.
# TYPE go_memstats_mcache_sys_bytes gauge
go_memstats_mcache_sys_bytes 16384
# HELP go_memstats_mspan_inuse_bytes Number of bytes in use by mspan structures.
# TYPE go_memstats_mspan_inuse_bytes gauge
go_memstats_mspan_inuse_bytes 37672
# HELP go_memstats_mspan_sys_bytes Number of bytes used for mspan structures obtained from system.
# TYPE go_memstats_mspan_sys_bytes gauge
go_memstats_mspan_sys_bytes 49152
# HELP go_memstats_next_gc_bytes Number of heap bytes when next garbage collection will take place.
# TYPE go_memstats_next_gc_bytes gauge
go_memstats_next_gc_bytes 4.473924e+06
# HELP go_memstats_other_sys_bytes Number of bytes used for other system allocations.
# TYPE go_memstats_other_sys_bytes gauge
go_memstats_other_sys_bytes 1.033983e+06
# HELP go_memstats_stack_inuse_bytes Number of bytes in use by the stack allocator.
# TYPE go_memstats_stack_inuse_bytes gauge
go_memstats_stack_inuse_bytes 360448
# HELP go_memstats_stack_sys_bytes Number of bytes obtained from system for stack allocator.
# TYPE go_memstats_stack_sys_bytes gauge
go_memstats_stack_sys_bytes 360448
# HELP go_memstats_sys_bytes Number of bytes obtained from system.
# TYPE go_memstats_sys_bytes gauge
go_memstats_sys_bytes 7.2174608e+07
# HELP go_threads Number of OS threads created.
# TYPE go_threads gauge
go_threads 7
# HELP promhttp_metric_handler_requests_in_flight Current number of scrapes being served.
# TYPE promhttp_metric_handler_requests_in_flight gauge
promhttp_metric_handler_requests_in_flight 1
# HELP promhttp_metric_handler_requests_total Total number of scrapes by HTTP status code.
# TYPE promhttp_metric_handler_requests_total counter
promhttp_metric_handler_requests_total{code="200"} 0
promhttp_metric_handler_requests_total{code="500"} 0
promhttp_metric_handler_requests_total{code="503"} 0应用层面指标
应用程序仅公开默认的 Go 指标。我们还可以注册自定义应用程序指定指标。如下示例应用程序公开了 myapp_processed_ops_total 计数器(/prometheus/concepts/metric_types#counter)，该计数器对到目前为止已处理的操作数量进行计数。每2秒，计数器增加1。
package main
import (
"net/http"
"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
func recordMetrics() {
//每2秒，计数器增加1。
go func() {
for {
opsProcessed.Inc()
time.Sleep(2 * time.Second)
}
}()
}
var (
opsProcessed = promauto.NewCounter(prometheus.CounterOpts{
Name: "myapp_processed_ops_total",
Help: "The total number of processed events",
})
)
func main() {
recordMetrics()
http.Handle("/metrics", promhttp.Handler())
http.ListenAndServe(":2112", nil)
}执行以下命令启动应用：
go run main.go执行以下命令，访问暴露的指标：
curl http://localhost:2112/metrics从输出结果我们可以看到 myapp_processed_ops_total 计数器相关的信息，包括帮助文本、类型信息、指标名和当前值。
如下所示：
......
# HELP myapp_processed_ops_total The total number of processed events
# TYPE myapp_processed_ops_total counter
myapp_processed_ops_total 4
......我们可以配置(/prometheus/prometheus/configuration/configuration#scrape_config) 一个 Prometheus 实例，从应用程序中获取指标。这是一个
prometheus.yml 配置示例：
scrape_configs:
- job_name: myapp
scrape_interval: 10s
static_configs:
- targets:
- 172.16.106.251:2112
总结
本文通过两个示例展示了如何将 Golang 相关的指标暴露给 Prometheus 监控服务。本文只使用了计数类型 Counter 的指标，对于其它场景可能还需要 Gauge，Histgram 以及 Summary 类型的指标类型。
源码地址：
参考资料：
- [1]：https://prometheus.io/docs/guides/go-application/
