probe.go

// Copyright 2016 The Prometheus Authors
// 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 main

import (
	"fmt"
	"net/http"

	"github.com/prometheus/common/log"
	"github.com/sclevine/agouti"
)

const msInSecond = 1000

// from https://www.w3.org/TR/navigation-timing/#sec-navigation-timing-interface
type navigationTimings struct {
	ConnectEnd                 float64
	ConnectStart               float64
	DomComplete                float64
	DomContentLoadedEventEnd   float64
	DomContentLoadedEventStart float64
	DomInteractive             float64
	DomLoading                 float64
	DomainLookupEnd            float64
	DomainLookupStart          float64
	FetchStart                 float64
	LoadEventEnd               float64
	LoadEventStart             float64
	NavigationStart            float64
	RedirectEnd                float64
	RedirectStart              float64
	RequestStart               float64
	ResponseEnd                float64
	ResponseStart              float64
	SecureConnectionStart      float64
	UnloadEventEnd             float64
	UnloadEventStart           float64
}

func probe(target string, w http.ResponseWriter) bool {
	// new page to ensure a clean session (no caching)
	options := []agouti.Option{
		agouti.Desired(agouti.NewCapabilities().Browser("chrome").With("javascriptEnabled")),
		agouti.Timeout(5),
	}
	page, err := driver.NewPage(options...)
	if err != nil {
		log.Error(err)
		return false
	}
	defer page.Destroy()

	err = page.Navigate(target)
	if err != nil {
		log.Error(err)
		return false
	}
	url, err := page.URL()
	if err != nil {
		log.Error(err)
		return false
	}
	if url != target {
		log.Errorf("got unexpected URL, ensure target accounts for any redirects; got %q, expected %q", url, target)
		return false
	}

	var timings *navigationTimings
	err = page.RunScript("return window.performance.timing;", nil, &timings)
	if err != nil {
		log.Error(err)
		return false
	}

	fmt.Fprintf(w, "navigation_timing_connect_end_seconds %f\n", timings.ConnectEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_connect_start_seconds %f\n", timings.ConnectStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_dom_complete_seconds %f\n", timings.DomComplete/msInSecond)
	fmt.Fprintf(w, "navigation_timing_dom_content_loaded_event_end_seconds %f\n", timings.DomContentLoadedEventEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_dom_content_loaded_event_start_seconds %f\n", timings.DomContentLoadedEventStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_dom_interactive_seconds %f\n", timings.DomInteractive/msInSecond)
	fmt.Fprintf(w, "navigation_timing_dom_loading_seconds %f\n", timings.DomLoading/msInSecond)
	fmt.Fprintf(w, "navigation_timing_domain_lookup_end_seconds %f\n", timings.DomainLookupEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_domain_lookup_start_seconds %f\n", timings.DomainLookupStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_fetch_start_seconds %f\n", timings.FetchStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_load_event_end_seconds %f\n", timings.LoadEventEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_load_event_start_seconds %f\n", timings.LoadEventStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_redirect_end_seconds %f\n", timings.RedirectEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_redirect_start_seconds %f\n", timings.RedirectStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_request_start_seconds %f\n", timings.RequestStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_response_end_seconds %f\n", timings.ResponseEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_response_start_seconds %f\n", timings.ResponseStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_secure_connection_start_seconds %f\n", timings.SecureConnectionStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_start_seconds %f\n", timings.NavigationStart/msInSecond)
	fmt.Fprintf(w, "navigation_timing_unload_event_end_seconds %f\n", timings.UnloadEventEnd/msInSecond)
	fmt.Fprintf(w, "navigation_timing_unload_event_start_seconds %f\n", timings.UnloadEventStart/msInSecond)

	logs, err := page.ReadAllLogs("browser")
	if err != nil {
		log.Error(err)
		return false
	}
	var warningCount, severeCount int
	for _, log := range logs {
		if log.Level == "WARNING" {
			warningCount++
		}
		if log.Level == "SEVERE" {
			severeCount++
		}
	}
	fmt.Fprintf(w, "browser_log_warning_count %d\n", warningCount)
	fmt.Fprintf(w, "browser_log_severe_count %d\n", severeCount)

	return true
}