<!-- Title: DBResolver Description: Resolve between read and write database automatically for gorm. go-gorm-v1 ,dbresolver Author: amitavaghosh1 -->

DBResolver

DBResolver for gorm v1. This adds functionality to switch between read and write databases.

Repo

Quick Start

Importing

go get github.com/go-gorm-v1/dbresolver@v1.0.3 

Usage

import (
  "github.com/go-gorm-v1/dbresolver"
  "github.com/jinzhu/gorm"
  _ "github.com/mattn/go-sqlite3"
)

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

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

    setDatabaseDefaults(masterDB)

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

    setDatabaseDefaults(replica)

    replicaDBs = append(replicaDBs, replica)

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

    setDatabaseDefaults(replica)

    replicaDBs = append(replicaDBs, replica)

    return dbresolver.Register(dbresolver.DBConfig{
        Master:   masterDB,
        Replicas: replicaDBs,
        // Policy: &dbresolver.RoundRobalancer{},
        // for existing database integration add this
        // DefaultMode: &dbresolver.DbWriteMode,
    })
}

db := Setup()

db.Raw(`SELECT * FROM users`)

Switching data source

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

// Raw By default uses read db
db.Raw(`SELECT * FROM users`)

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

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

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

This uses write mode for all Query methods apart from Where

• Find
• First
• Last
• Take
• Count

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
}