// dbasik provides a service with which to convert spreadsheets containing
// data to JSON for further processing.
// Copyright (C) 2024 M R Lemon
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// Package main is the entry point for dbasik.
// It provides the main functionality for the dbasik application.
package main
import (
"context"
"database/sql"
"flag"
"fmt"
"log"
"log/slog"
"net/http"
"os"
"time"
"github.com/joho/godotenv"
_ "github.com/lib/pq"
)
const version = "0.0.1"
// holds the config for our application
// We will read this from the command line flags when we run the application
type config struct {
port int
env string
db struct {
dsn string
maxOpenConns int
maxIdleConns int
maxIdleTime string
}
}
// This application struct holds the dependencies for our HTTP handlers, helpers and
// middleware.
type application struct {
config config
logger *slog.Logger
models Models
}
func main() {
// Instance of config
var cfg config
err := godotenv.Load()
if err != nil {
log.Fatal("Cannot load .env file - is it present?")
}
// Read the flags into the config struct. Defaults are provided if none given.
flag.IntVar(&cfg.port, "port", 5000, "API server port")
flag.StringVar(&cfg.env, "env", "development", "Environment (development|staging|production)")
flag.StringVar(&cfg.db.dsn, "db-dsn", os.Getenv("DBASIK_DB_DSN"), "PostgreSQL DSN")
//Read connection pool settings (explained in Configuring the pool in the book)
flag.IntVar(&cfg.db.maxOpenConns, "db-max-open-conns", 25, "PostgreSQL max open connections")
flag.IntVar(&cfg.db.maxIdleConns, "db-max-idle-conns", 25, "PostgreSQL max idle connections")
flag.StringVar(&cfg.db.maxIdleTime, "db-max-idle-time", "15m", "PostgreSQL max connection idle time")
flag.Parse()
// Initialize a new structured logger which writes to stdout
logger := slog.New(slog.NewTextHandler(os.Stdout, nil))
// set up the database pool
db, err := openDB(cfg)
if err != nil {
logger.Error(err.Error())
os.Exit(1)
}
defer db.Close()
logger.Info("database connection pool established")
// An instance of application struct, containing the config struct and the logger
app := &application{
config: cfg,
logger: logger,
models: NewModels(db),
}
// Declare an http server which listens provided in the config struct and has
// sensible timeout settings and writes log messages to the structured logger at
// Error level.
srv := &http.Server{
Addr: fmt.Sprintf(":%d", cfg.port),
Handler: app.routes(),
IdleTimeout: time.Minute,
ReadTimeout: 5 * time.Second,
WriteTimeout: 10 * time.Second,
ErrorLog: slog.NewLogLogger(logger.Handler(), slog.LevelError),
}
logger.Info("starting server", "addr", srv.Addr, "env", cfg.env)
err = srv.ListenAndServe()
logger.Error(err.Error())
os.Exit(1)
}
func openDB(cfg config) (*sql.DB, error) {
db, err := sql.Open("postgres", cfg.db.dsn)
if err != nil {
return nil, err
}
// set up pool config
db.SetMaxOpenConns(cfg.db.maxOpenConns)
db.SetMaxIdleConns(cfg.db.maxIdleConns)
duration, err := time.ParseDuration(cfg.db.maxIdleTime)
if err != nil {
return nil, err
}
db.SetConnMaxIdleTime(duration)
// create a context with a 5 second timeout
// if the database hasn't connected within this time, there is a problem
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
err = db.PingContext(ctx)
if err != nil {
return nil, err
}
return db, nil
}
