httpserver/middleware/db/db.go

// Package db is an middleware that manages multiple database pools and provides applications with an way to access the database
package db

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"sync"

	"github.com/gin-gonic/gin"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/jackc/tern/v2/migrate"
	"github.com/rs/zerolog/log"
	"go.sebtobie.de/httpserver/middleware"
)

// ContextKey is the key that is used in a gin.Context to get the Middleware
const ContextKey string = "db"

// ConnGet is an function that returns an connection instance.
type ConnGet func(string) *pgxpool.Conn

var _ ConnGet = NewMiddleware().GetConn
var _ middleware.Middleware = &Middleware{}
var _ middleware.PostSetupMiddleware = &Middleware{}

// GetConnection is an simple helper function that returns an connection to the db
func GetConnection(c *gin.Context, db string) (*pgxpool.Conn, error) {
	if co, ok := c.Get(ContextKey); ok {
		return co.(ConnGet)(db), nil
	}
	return nil, errors.New("No db.Middleware set up. ")
}

// Middleware return a handler that sets the db into the context of every request.
// uri is an url in the form dbtype:connectargs
type Middleware struct {
	databases map[string]*pgxpool.Pool
	lock      sync.Mutex
}

// NewMiddleware return an initialized Middleware Object.
func NewMiddleware() *Middleware {
	return &Middleware{
		databases: make(map[string]*pgxpool.Pool),
	}
}

// AddDB adds an db connection to the middleware.
func (m *Middleware) AddDB(name, uri string) (err error) {
	m.lock.Lock()
	if m.databases == nil {
		m.databases = map[string]*pgxpool.Pool{}
	}
	m.lock.Unlock()
	var (
		db *pgxpool.Pool
	)
	if err != nil {
		log.Error().Err(err).Msg("Could not open the database")
		return err
	}
	db, err = pgxpool.New(context.TODO(), uri)
	if err != nil {
		log.Error().Err(err).Msg("Could not open the database")
		return err
	}
	m.lock.Lock()
	defer m.lock.Unlock()
	if olddb, found := m.databases[name]; found {
		olddb.Close()
	}
	m.databases[name] = db
	return
}

func (m *Middleware) getconn(name string) *pgxpool.Conn {
	if db, found := m.databases[name]; found {
		conn, err := db.Acquire(context.TODO())
		if err != nil {
			log.Error().Err(err).Msgf("Could not get the connection from the pool %s", name)
			return nil
		}
		return conn
	}
	return nil
}

// GetConn returns a connection from the specified database or if not found one of the default database.
func (m *Middleware) GetConn(name string) *pgxpool.Conn {
	m.lock.Lock()
	defer m.lock.Unlock()
	if conn := m.getconn(name); conn != nil {
		return conn
	}
	conn := m.getconn("default")
	return conn
}

// Gin is the Entrypoint for Gin.
func (m *Middleware) Gin(c *gin.Context) {
	c.Set(ContextKey, m.GetConn)
}

// Setup adds the connections from the configfile into the middleware
func (m *Middleware) Setup(mc middleware.Config) {
	for key, value := range mc {
		dsn := value.(string)
		err := m.AddDB(key, dsn)
		if err != nil {
			log.Error().Err(err).Msg("Failed to parse the config")
		}
	}
}

// Defaults returns an default config for connections
func (*Middleware) Defaults() middleware.Config {
	return map[string]any{
		"default": "host=/run/postgresql port=5432 dbname=httpserver",
	}
}

// Teardown closes the DBConnection
func (m *Middleware) Teardown() {
	for name, pool := range m.databases {
		log.Info().Msgf("Starting to close databasepool %s", name)
		pool.Close()
		log.Info().Msgf("Closed Databasepool %s", name)
	}
}

// PostSetup is an function for getting the migrations of the site
func (m *Middleware) PostSetup(sites []any) (err error) {
	m.lock.Lock()
	defer m.lock.Unlock()
	var (
		conn *pgxpool.Conn
		mig  *migrate.Migrator
		db   *pgxpool.Pool
	)
	for _, s := range sites {

		if site, ok := s.(MigrationSite); ok {

			db, ok = m.databases[site.Database()]
			if !ok {
				return fmt.Errorf("Failed to get the database. The Databasepool %s does not exist", site.Database())
			}
			conn, err = db.Acquire(context.TODO())
			if err != nil {
				return
			}
			defer conn.Release()
			mig, err = site.Migrations(conn.Conn())
			err = mig.Migrate(context.TODO())
			if err != nil {
				return
			}
			if poolsite, ok := s.(PoolSite); ok {
				poolsite.Pool(m.databases[site.Database()])
			}
		}
	}
	return
}

func logmigrations(version int32, name, dir string, sql string) {
	log.Info().Int32("version", version).Str("name", name).Str("dir", dir).Msgf("Running Migration %s with version %d in %sward direction", name, version, dir)
}

// MigrationSite is an interface for Sites that use an database.
// this enables sites to provide database migrations.
type MigrationSite interface {
	Database() string
	Migrations(*pgx.Conn) (*migrate.Migrator, error)
}

// PoolSite is an interface for site that need access to the pool outside of requests
type PoolSite interface {
	MigrationSite
	Pool(*pgxpool.Pool)
}

// SetupMigrator sets up the migrator to migrate the database.
func SetupMigrator(prefix string, connection *pgx.Conn, migrations fs.FS) (mig *migrate.Migrator, err error) {
	mig, err = migrate.NewMigratorEx(
		context.TODO(),
		connection,
		prefix+"version",
		&migrate.MigratorOptions{
			DisableTx: false,
		},
	)
	if err != nil {
		log.Error().Err(err).Msg("Error while creating the migrator")
		return
	}
	mig.OnStart = logmigrations
	mig.Data["prefix"] = prefix
	err = mig.LoadMigrations(migrations)
	if err != nil {
		log.Error().Err(err).Msg("Error while loading migrations")
		return
	}
	log.Trace().Interface("migrations", mig.Migrations).Interface("data", mig.Data).Err(err).Send()
	return
}