DBResolver

Switch between read and write databases. Coalesce requests.

Repo

Quick Start

Importing

go get github.com/go-batteries/dbresolver@latest 

Usage

import (
  "github.com/go-batteries/dbresolver"
  _ "github.com/mattn/go-sqlite3"
)

func setDatabaseDefaults(db *sql.DB) {
	db.SetMaxIdleConns(MAX_IDLE_CONNECTIONS)
	db.SetConnMaxLifetime(CONN_MAX_LIFETIME)
	db.SetMaxOpenConns(MAX_OPEN_CONNECTIONS)
	db.LogMode(true)
}

func Setup() *dbresolver.Database {
    masterDB, err := sql.Open("sqlite3", "./testdbs/users_write.db")
    if err != nil {
      log.Fatal("failed to connect to db", err)
    }

    setDatabaseDefaults(masterDB)

    replicaDBs := []*dbresolver.ResolverDB{}
    
    replica, err := sql.Open("sqlite3", "./testdbs/users_read_a.db")
    if err != nil {
      log.Fatal("failed to connect to db", err)
    }

    setDatabaseDefaults(replica)
    replicaDBs = append(replicaDBs, dbresolver.AsSyncReplica(replica, "users_read_replica1"))

    replica, err = sql.Open("sqlite3", "./testdbs/users_read_b.db")
    if err != nil {
      log.Fatal("failed to connect to db", err)
    }

    setDatabaseDefaults(replica)
    replicaDBs = append(replicaDBs, dbresolver.AsReplica(replica, "users_read_replica2"))


    return dbresolver.Register(dbresolver.DBConfig{
        Master:   dbresolver.AsMaster(masterDB, "users_wrtie"),
        Replicas: replicaDBs,
        // Policy: &dbresolver.RoundRobalancer{},
        // for existing database integration, default mode to write
        // DefaultMode: &dbresolver.DbWriteMode,
        // MaxIdleConnections: dbresolver.ToPtr(30),
        // MaxOpenConnections: ,
        // ConnectionMaxLifeTime: ,
    })
}

db := Setup()

db.QueryRow(`SELECT * FROM users`)

Switching data source

It is possible to provide the option to use read or write forcefully.

// Use write db
db.WithMode(dbresolver.DBWriteMode).QueryRow(`SELECT * FROM users`)

// Use read db
db.WithMode(dbresolver.DBReadMode).Exec(`DELETE FROM users`) // error
db.WithMode(dbresolver.DBWriteMode).Exec(`DELETE FROM users`) // works

// if you need to work with DML queries on read instance
// use the sql.DB object

replicaDB.DB.Exec(`DELETE FROM users`);

It is also possible to set the default mode to read/write mode.

dbresolver.DBConfig {
    DefaultMode: &dbresolver.DbWriteMode
}

Load Balancing

By default we have two balancers

// RandomBalancer
dbresolver.DBConfig{
    Policy: &dbresolver.RoundRobalancer{}
}

// RandomBalancer
dbresolver.DBConfig{
    Policy: &dbresolver.RandomBalancer{}
}

You can provide your own load balancer. The Balancer interface is defined as such

type Balancer interface {
    Get() int64
}