template-exporter/collector/collector.go

/*
Copyright 2024 Adora Laura Kalb <adora@lila.network>

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 collector

import (
	"context"
	"encoding/json"
	"io"
	"net/http"
	"net/netip"
	"time"

	"github.com/go-kit/log"
	"github.com/go-kit/log/level"
	"github.com/prometheus/client_golang/prometheus"
	"golang.adora.codes/template-exporter/cache"
	"golang.adora.codes/template-exporter/models"
)

type Metrics struct {
	NtpppolServerScore prometheus.Gauge
}

type Collector struct {
	ctx     context.Context
	target  netip.Addr
	logger  log.Logger
	metrics Metrics
}

func New(ctx context.Context, target netip.Addr, logger log.Logger, metrics Metrics) *Collector {
	return &Collector{ctx: ctx, target: target, logger: logger, metrics: metrics}
}

// Describe implements Prometheus.Collector.
func (c Collector) Describe(ch chan<- *prometheus.Desc) {
	ch <- prometheus.NewDesc("dummy", "dummy", nil, nil)
}

// Collect implements Prometheus.Collector.
func (c Collector) Collect(ch chan<- prometheus.Metric) {
	logger := log.With(c.logger, "module", "scraper")
	level.Debug(logger).Log("msg", "Starting scrape")
	start := time.Now()
	c.collect(ch, logger)
	duration := time.Since(start).Seconds()
	level.Debug(logger).Log("msg", "Finished scrape", "duration_seconds", duration)
}

func (c Collector) collect(ch chan<- prometheus.Metric, logger log.Logger) {
	score, err := cache.GlobalScoreCache.Get(c.target)
	if err == nil {
		level.Debug(logger).Log("msg", "Serving score from cache",
			"server", c.target.String(), "score", score.Score)

		serverScoreMetric := prometheus.NewDesc("template_server_score",
			"Shows the server score currently assigned at template.org",
			nil, nil)

		m1 := prometheus.MustNewConstMetric(serverScoreMetric, prometheus.GaugeValue, score.Score)
		m1 = prometheus.NewMetricWithTimestamp(time.Now(), m1)
		ch <- m1
		return
	}

	level.Debug(logger).Log("msg", "Cache miss, querying API",
		"server", c.target.String())

	var serverApiScore float64 = 0
	const apiEndpoint = "https://www.template.org/scores/"
	const apiQuery = "/json?limit=1&monitor=24"

	url := apiEndpoint + c.target.String() + apiQuery

	client := &http.Client{}
	req, err := http.NewRequest("GET", url, nil)

	if err != nil {
		level.Error(logger).Log("msg", "Error sending HTTP request", "url", url, "message", err)
		return
	}
	res, err := client.Do(req)
	if err != nil {
		level.Error(logger).Log("msg", "Error in HTTP response", "error", err)
		return

	}
	defer res.Body.Close()

	body, err := io.ReadAll(res.Body)
	if err != nil {
		level.Error(logger).Log("msg", "Error reading HTTP response body", "error", err)
		return
	}

	var response models.ApiResponse

	err = json.Unmarshal(body, &response)
	if err != nil {
		level.Error(logger).Log("msg", "Error unmarshaling JSON body", "error", err)
		return
	}

	serverApiScore = response.History[0].Score

	cache.GlobalScoreCache.Add(serverApiScore, c.target, time.Now())
	level.Debug(logger).Log("msg", "Added score to cache",
		"server", c.target.String(), "score", score.Score)

	// TODO: Test or delete
	serverScoreMetric := prometheus.NewDesc("template_server_score",
		"Shows the server score currently assigned at template.org",
		nil, nil)

	// TODO: Test or delete
	//c.metrics.NtpppolServerScore.Add(serverApiScore)

	// TODO: Test or delete
	//Write latest value for each metric in the prometheus metric channel.
	//Note that you can pass CounterValue, GaugeValue, or UntypedValue types here.
	m1 := prometheus.MustNewConstMetric(serverScoreMetric, prometheus.GaugeValue, serverApiScore)
	m1 = prometheus.NewMetricWithTimestamp(time.Now(), m1)
	ch <- m1
}