Nap
Nap is a library that abstracts access to master-slave physical SQL servers topologies as a single logical database mimicking the standard sql.DB APIs.
Nap requires Go version 1.8 or greater.
Install
$ go get github.com/tsenart/nap
Usage
package main
import (
"log"
"github.com/tsenart/nap"
_ "github.com/go-sql-driver/mysql" // Any sql.DB works
)
func main() {
// The first DSN is assumed to be the master and all
// other to be slaves
dsns := "tcp://user:password@master/dbname;"
dsns += "tcp://user:password@slave01/dbname;"
dsns += "tcp://user:password@slave02/dbname"
db, err := nap.Open("mysql", dsns)
if err != nil {
log.Fatal(err)
}
if err := db.Ping(); err != nil {
log.Fatalf("Some physical database is unreachable: %s", err)
}
// Read queries are directed to slaves with Query and QueryRow.
// Always use Query or QueryRow for SELECTS
// Load distribution is round-robin only for now.
var count int
err = db.QueryRow("SELECT COUNT(*) FROM sometable").Scan(&count)
if err != nil {
log.Fatal(err)
}
// Write queries are directed to the master with Exec.
// Always use Exec for INSERTS, UPDATES
err = db.Exec("UPDATE sometable SET something = 1")
if err != nil {
log.Fatal(err)
}
// Prepared statements are aggregates. If any of the underlying
// physical databases fails to prepare the statement, the call will
// return an error. On success, if Exec is called, then the
// master is used, if Query or QueryRow are called, then a slave
// is used.
stmt, err := db.Prepare("SELECT * FROM sometable WHERE something = ?")
if err != nil {
log.Fatal(err)
}
// Transactions always use the master
tx, err := db.Begin()
if err != nil {
log.Fatal(err)
}
// Do something transactional ...
if err = tx.Commit(); err != nil {
log.Fatal(err)
}
// If needed, one can access the master or a slave explicitly.
master, slave := db.Master(), db.Slave()
}
Todo
- Support other slave load balancing algorithms.
License
See LICENSE