main.go

package main

import (
	"context"
	"flag"
	"fmt"
	"github.com/kelseyhightower/envconfig"
	"github.com/sqooba/go-common/logging"
	"github.com/sqooba/go-common/version"
	"net/http"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"
)

var (
	setLogLevel = flag.String("set-log-level", "", "Change log level. Possible values are trace,debug,info,warn,error,fatal,panic")
	log         = logging.NewLogger()
)

type envConfig struct {
	Port             string `envconfig:"PORT" default:"8080"`
	LogLevel         string `envconfig:"LOG_LEVEL" default:"info"`
	MetricsNamespace string `envconfig:"METRICS_NAMESPACE" default:"dockerlabelsdiscovery"`
	MetricsSubsystem string `envconfig:"METRICS_SUBSYSTEM" default:""`
	MetricsPath      string `envconfig:"METRICS_PATH" default:"/metrics"`

	PrometheusConfigFilePath       string            `envconfig:"PROMETHEUS_CONFIG_FILE_PATH"`
	PrometheusAddContainerMetadata bool              `envconfig:"PROMETHEUS_ADD_CONTAINER_METADATA"`                // adds container_id and container name to the target labels.
	DockerNetworkName              string            `envconfig:"DOCKER_NETWORK_NAME" default:"monitoring_default"` // docker network to search ip from.
	DockerNetworkStrict            bool              `envconfig:"DOCKER_NETWORK_STRICT"`                            // Restrict to the DockerNetworkName, or use it as preferred network but try to best effort to find a ip on another network.
	DockerPollFrequency            time.Duration     `envconfig:"DOCKER_POLL_FREQUENCY" defaults:"5m"`
	PrometheusCommonLabels         map[string]string `envconfig:"PROMETHEUS_COMMON_LABELS"` // Comma separated key:value to add to all targets.
}

func main() {
	log.Println("prometheus-docker-labels-discovery application is starting...")
	log.Printf("Version    : %s", version.Version)
	log.Printf("Commit     : %s", version.GitCommit)
	log.Printf("Build date : %s", version.BuildDate)
	log.Printf("OSarch     : %s", version.OsArch)

	var env envConfig
	if err := envconfig.Process("", &env); err != nil {
		log.Printf("[ERROR] Failed to process env var: %s\n", err)
		return
	}

	flag.Parse()
	err := logging.SetLogLevel(log, env.LogLevel)
	if err != nil {
		log.Fatalf("Logging level %s do not seem to be right. Err = %v", env.LogLevel, err)
	}

	if *setLogLevel != "" {
		logging.SetRemoteLogLevelAndExit(log, env.Port, *setLogLevel)
	}

	// Special endpoint to change the verbosity at runtime, i.e. curl -X PUT --data debug ...
	logging.InitVerbosityHandler(log, http.DefaultServeMux)
	initPrometheus(env, http.DefaultServeMux)
	signalChan := make(chan os.Signal, 1)
	signal.Notify(signalChan, syscall.SIGINT, syscall.SIGTERM)
	var wg sync.WaitGroup

	promFileHandler, err := newPromFileHandler(env)
	if err != nil {
		log.Fatalf("Got an exception while initialising prometheus file handler. Err = %v", err)
	}

	dockerHandler, err := newDockerHandler(env, promFileHandler)
	if err != nil {
		log.Fatalf("Got an exception while initialising docker handler. Err = %v", err)
	}
	go dockerHandler.handle()

	s := http.Server{Addr: fmt.Sprint(":", env.Port)}
	go func() {
		log.Fatal(s.ListenAndServe())
	}()

	<-signalChan
	log.Printf("Shutdown signal received, exiting...")

	err = s.Shutdown(context.Background())
	if err != nil {
		log.Fatalf("Got an error while shutting down: %v\n", err)
	}

	// Wait for processing to complete properly
	wg.Wait()
}