I'm trying to register the Prometheus handler to track some metrics from the applicati

Ok, I managed to make it work 😄 <div class="highlight highlight-source-go notrans

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🤔 How to register a Prometheus handler about fiber HOT 10 CLOSED

gofiber commented on April 30, 2024 2

🤔 How to register a Prometheus handler

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Comments (10)

ansrivas commented on April 30, 2024 3

We have to think about that, but maybe its better to fix this in a wrapper for Prometheus.

PS: You have a bug in your code: 🐝

@Fenny I have implemented the prometheus middleware with some basic defaults here.
https://github.com/ansrivas/fiberprometheus

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ganglio commented on April 30, 2024 2

Ok, I managed to make it work 😄

package middlewares

import (
  "fmt"

  "github.com/gofiber/fiber"
  "github.com/prometheus/client_golang/prometheus"
  "github.com/prometheus/client_golang/prometheus/promhttp"
  "github.com/valyala/fasthttp/fasthttpadaptor"
)

var (
  p = fasthttpadaptor.NewFastHTTPHandler(
    promhttp.HandlerFor(
      prometheus.DefaultGatherer,
      promhttp.HandlerOpts{
        // Opt into OpenMetrics to support exemplars.
        EnableOpenMetrics: true,
      },
    ),
  )

  errCnt = prometheus.NewCounterVec(
    prometheus.CounterOpts{
      Name: "promhttp_metric_handler_errors_total",
      Help: "Total number of internal errors encountered by the promhttp metric handler.",
    },
    []string{"status", "method", "path"},
  )
)

func init() {
  prometheus.MustRegister(errCnt)
}

func PrometheusHandler(c *fiber.Ctx) {
  p(c.Fasthttp)
}

func Prometheus(c *fiber.Ctx) {
  sc := c.Fasthttp.Response.StatusCode()
  me := c.Fasthttp.Method()
  pa := c.Fasthttp.Path()
  errCnt.WithLabelValues(fmt.Sprintf("%d", sc), string(me), string(pa)).Add(1)
  c.Next()
}

Only caveat is that all the routes must have a defer c.Next() and the config looks like this:

...

app.Get("/metrics", middlewares.PrometheusHandler)
app.Get("/", func(c *fiber.Ctx) {
  defer c.Next()
  c.Send("🐝")}
)
app.Use(middlewares.Prometheus)
app.Listen(3000)

...

It would be amazing to have support for "afterwares" that are always executed after everything.

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ganglio commented on April 30, 2024 1

ps: Brilliant work, BTW 😄

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welcome commented on April 30, 2024

Thanks for opening your first issue here! 🎉 Be sure to follow the issue template!

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Fenny commented on April 30, 2024

@ganglio, make sure you are using the latest version:
go get -u github.com/gofiber/fiber

When I run your code I get the following output, could you tell me what variable is missing/incorrect?

package main

import (
	"github.com/gofiber/fiber"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/valyala/fasthttp/fasthttpadaptor"
)

func main() {
	app := fiber.New()

	p := fasthttpadaptor.NewFastHTTPHandler(promhttp.Handler())

	app.Get("/metrics", func(c *fiber.Ctx) {
		p(c.Fasthttp)
	})

	app.Get("/", func(c *fiber.Ctx) {
		c.Send("Hello, World!")
	})

	app.Get("/404", func(c *fiber.Ctx) {
		c.Status(404).Send("You just lost us an unpaid employee.")
	})

	app.Listen(3000)
}

http://localhost:3000/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 9
# HELP go_info Information about the Go environment.
# TYPE go_info gauge
go_info{version="go1.13.5"} 1
# HELP go_memstats_alloc_bytes Number of bytes allocated and still in use.
# TYPE go_memstats_alloc_bytes gauge
go_memstats_alloc_bytes 1.166264e+06
# 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 1.166264e+06
# 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 1.443579e+06
# HELP go_memstats_frees_total Total number of frees.
# TYPE go_memstats_frees_total counter
go_memstats_frees_total 222
# 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 2.240512e+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 1.166264e+06
# 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 6.4397312e+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 2.2528e+06
# HELP go_memstats_heap_objects Number of allocated objects.
# TYPE go_memstats_heap_objects gauge
go_memstats_heap_objects 4380
# 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 6.4397312e+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 6.6650112e+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 4602
# 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 13888
# 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 25160
# 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 32768
# 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 1.051133e+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 458752
# 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 458752
# HELP go_memstats_sys_bytes Number of bytes obtained from system.
# TYPE go_memstats_sys_bytes gauge
go_memstats_sys_bytes 7.189324e+07
# HELP go_threads Number of OS threads created.
# TYPE go_threads gauge
go_threads 8
# HELP process_cpu_seconds_total Total user and system CPU time spent in seconds.
# TYPE process_cpu_seconds_total counter
process_cpu_seconds_total 0
# HELP process_max_fds Maximum number of open file descriptors.
# TYPE process_max_fds gauge
process_max_fds 1024
# HELP process_open_fds Number of open file descriptors.
# TYPE process_open_fds gauge
process_open_fds 8
# HELP process_resident_memory_bytes Resident memory size in bytes.
# TYPE process_resident_memory_bytes gauge
process_resident_memory_bytes 1.0747904e+07
# HELP process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE process_start_time_seconds gauge
process_start_time_seconds 1.58230736989e+09
# HELP process_virtual_memory_bytes Virtual memory size in bytes.
# TYPE process_virtual_memory_bytes gauge
process_virtual_memory_bytes 5.82090752e+08
# HELP process_virtual_memory_max_bytes Maximum amount of virtual memory available in bytes.
# TYPE process_virtual_memory_max_bytes gauge
process_virtual_memory_max_bytes -1
# 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

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ganglio commented on April 30, 2024

@Fenny if you keep requesting /metrics you'll see the promhttp_metric_handler_requests_total{code="200"} increase.
It doesn't happen if you query / or /404 (do it a number of times as the metric increase by 1 every time you request the /metrics endpoint.

From what I understand, the promhttp is used as a wrapper around a router. In the case of Fiber it's only added as a single route thus, while it measures correctly the health of the application (memory, goroutines, etc) it doesn't count the requests correctly.

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Fenny commented on April 30, 2024

We have to think about that, but maybe its better to fix this in a wrapper for Prometheus.

PS: You have a bug in your code: 🐝

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asad-awadia commented on April 30, 2024

@Fenny any updates on this?

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calbot commented on April 30, 2024

There's no simple way to create separate metrics endpoints when you're running with prefork.
It would be nice if each child had it's own assigned number 0,1,2....n so it could use this to pick a port for the /metrics endpoint.
I is there a way to get the child "index". I don't think you could get it it reliably from the process id of the child. I could do some janky solution where the children send there procid to the master and the master sends back their port number for metrics.

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calbot commented on April 30, 2024

Here's my solution to get metrics endpoints setup on consistent port numbers when using prefork.
It requires Redis...

//Before we start the "actual" webserver start the metrics endpoint servers...
if !fiber.IsChild() {
	//Master
	go func() {
		//60338=GOWEB
		//Expect "max" child processes
		childProcCount := runtime.GOMAXPROCS(0)
		startingPort := 60338
		logger.Logger.Info("Setting up child metrics port numbers", zap.Int("childProcCount", childProcCount))
		childProcIdChan := RedisClient.PSubscribe(context.TODO(), "goweb.metricsSetup.childPid")
		for i := 0; i < childProcCount; i++ {
			//Recieve the clients process id
			evt := <-childProcIdChan.Channel()
			procID := evt.Payload
			// logger.Logger.Info("recieved a request for a /metrics port number from a child process", zap.String("procID", procID))

			//Send the client a port number to use for it's prometheus /metrics server
			RedisClient.Publish(context.TODO(), "goweb.metricsSetup.childPort."+procID, strconv.Itoa(startingPort+i))
		}

		err := childProcIdChan.Close()
		if err != nil {
			logger.Logger.Error("Error closing the channel for child process IDs", zap.Error(err))
		}
	}()
} else {
	//Child
	childPid := os.Getpid()
	go func() {
		// logger.Logger.Info("Child waiting to rec port number", zap.Int("childProcessID", childPid))

		//First start listenting for our port to use for /metrics
		portChannel := RedisClient.PSubscribe(context.TODO(), "goweb.metricsSetup.childPort."+strconv.Itoa(childPid))
		evt := <-portChannel.Channel()
		err := portChannel.Close()
		if err != nil {
			logger.Logger.Error("Error closing the channel for recieving the prometheus /metrics port number", zap.Error(err))
		}

		portNumStr := evt.Payload
		logger.Logger.Info("Child starting metrics endpoint", zap.String("url", "http://localhost:"+portNumStr+"/metrics"), zap.Int("childProcessID", childPid))
		http.Handle("/metrics", promhttp.Handler())

		//Run the metrics http server alongside fiber on a different port
		http.ListenAndServe(":"+portNumStr, nil)
	}()

	go func() {
		//Wait for master process to start listening on redis channel "goweb.metricsSetup.childPid"
		time.Sleep(5 * time.Second)

		// logger.Logger.Info("Child requesting port number from master", zap.Int("childProcessID", childPid))

		//Send the master our PID
		RedisClient.Publish(context.TODO(), "goweb.metricsSetup.childPid", strconv.Itoa(childPid))
	}()
}

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🤔 How to register a Prometheus handler about fiber HOT 10 CLOSED

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