67 lines
2.6 KiB
Go
67 lines
2.6 KiB
Go
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// Package database owns everything related to talking to MySQL: opening
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// the connection pool and running startup migrations. Nothing outside this
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// package (and the repositories in internal/models) should import the
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// MySQL driver directly - that keeps the database technology an
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// implementation detail hidden behind a plain *sql.DB.
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package database
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import (
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"context"
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"database/sql"
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"fmt"
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"time"
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// Blank import: we never call anything from this package by name.
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// Importing it purely for its side effect - its init() function
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// registers "mysql" as a driver name with database/sql, which is what
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// lets sql.Open("mysql", ...) below work at all.
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_ "github.com/go-sql-driver/mysql"
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"git.hamidsoltani.com/hamid/go-simple-api/internal/config"
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)
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// NewMySQL opens a connection pool to MySQL, configures reasonable pool
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// limits, and verifies connectivity with a real ping before returning -
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// so a bad connection string / unreachable database fails loudly at
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// startup instead of silently on the first real query.
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func NewMySQL(ctx context.Context, cfg config.Config) (*sql.DB, error) {
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// DSN = Data Source Name. Format: user:password@tcp(host:port)/dbname?options
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// parseTime=true tells the driver to convert MySQL DATETIME/TIMESTAMP
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// columns into Go time.Time values automatically.
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dsn := fmt.Sprintf(
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"%s:%s@tcp(%s:%s)/%s?parseTime=true",
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cfg.DBUser, cfg.DBPassword, cfg.DBHost, cfg.DBPort, cfg.DBName,
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)
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// sql.Open does NOT connect yet - it just validates the DSN and
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// returns a *sql.DB, which represents a pool of connections managed
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// for you, not a single live connection.
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db, err := sql.Open("mysql", dsn)
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if err != nil {
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return nil, fmt.Errorf("open mysql: %w", err)
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}
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// Pool tuning:
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// MaxOpenConns - hard ceiling on simultaneous connections, protects
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// the database from being overwhelmed by this app.
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// MaxIdleConns - how many connections to keep warm/ready even when
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// idle, so we don't pay reconnect cost constantly.
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// ConnMaxLifetime - force connections to be recycled periodically,
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// useful behind load balancers or if MySQL itself
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// closes long-lived idle connections.
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db.SetMaxOpenConns(10)
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db.SetMaxIdleConns(5)
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db.SetConnMaxLifetime(5 * time.Minute)
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// Give the ping a hard deadline instead of letting it hang forever if
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// the database host is unreachable.
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pingCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
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defer cancel()
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if err := db.PingContext(pingCtx); err != nil {
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return nil, fmt.Errorf("ping mysql: %w", err)
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}
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return db, nil
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}
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