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urlshortener.go
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urlshortener.go
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package main
// URLshortener is a microservice to shorten long URLs
// and to handle the redirection by generated short URLs.
//
// See details in README.md
//
// This file contains the main routine
import (
"fmt"
"log"
"net/http"
"os"
"os/signal"
"syscall"
"time"
)
var (
version string = "local_build"
)
func main() {
if len(os.Args) == 2 && os.Args[1] == "-v" {
fmt.Printf("URLshortener %s\n", version)
os.Exit(0)
}
// log the version
log.Printf("URLshortener %s", version)
// set logging format
log.SetFlags(log.Ldate | log.Ltime | log.Lmicroseconds | log.Lshortfile)
// get exiting error
err := doMain()
if err != http.ErrServerClosed {
panic(err)
} else {
log.Println(err)
}
}
// doMain performs all preparation and starts server
func doMain() error {
// get the configuration variables
config, err := readConfig()
if err != nil {
return fmt.Errorf("configuration read error: %w", err)
}
// initialize database connection
tokenDB, err := NewTokenDB(config.RedisAddrs, config.RedisPassword)
if err != nil {
return fmt.Errorf("database interface creation error: %w", err)
}
defer func() {
// close DB connection
err = tokenDB.Close()
if err != nil {
log.Printf("DB connection close error: %v", err)
}
}()
return stratService(config, tokenDB)
}
func stratService(config *Config, tokenDB TokenDB) error {
// make service handler
handler := NewHandler(config, tokenDB, NewShortToken(config.TokenLength))
handlerErr := make(chan error, 1)
// start service
go func() {
handlerErr <- handler.start()
}()
// wait for server start
time.Sleep(300 * time.Millisecond)
if err := handler.healthCheck(); err != nil {
fmt.Printf("initial health-check failed: %v\nexiting...\n", err)
} else {
log.Println("initial health-check successfuly passed")
c := make(chan os.Signal, 1)
signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
// sleep until a signal is received.
<-c
}
// Close service
handler.stop()
return <-handlerErr
}