Go and MongoDB simple example
05 February 2017Both Golang and MongoDB are a perfect pair for rapid application development and building things for scale. They both have native features that allows you to focus on your application. When choosing a database, make sure that MongoDB fits your requirements as it is not a one-size-fits all solution. Read the official docs on its design and use cases. In this post, we’ll go from Installation to building a CRUD.
Install and Start MongoDB
Install MongoDB on Mac
brew update
brew install mongodb
Create Data Directory
Before you start MongoDB for the first time, create the directory where
mongod process will write. By default this is in /data/db. If you
create a different one, specify that in the dbpath option when starting a
mongod process.
Setup Permissions
Before running mongod, make sure the user account that will run it has read
and write permissions for the directory.
# change owner of everything in /data to current user
sudo chown -R $USER /data/db
# allow user to have read/write access
sudo chmod -R u+rw /data/db
Run MongoDB Server
mongod
That’s it! However, if you have changed the directory from the default, you will
have to specify it, like this: mongod --dbpath /path/to/dir
Connect to the Shell
Typically, you’d connect through your application, but if you’d like to connect to the MongoDB server you just ran, execute the MongoDB shell client:
mongo
Go
NOTE: this section is still in development
Get mongo drivers for go.
go get gopkg.in/mgo.v2
Sample CRUD
package main
import (
"fmt"
"time"
"gopkg.in/mgo.v2"
"gopkg.in/mgo.v2/bson"
)
type Game struct {
Winner string `bson:"winner"`
OfficialGame bool `bson:"official_game"`
Location string `bson:"location"`
StartTime time.Time `bson:"start"`
EndTime time.Time `bson:"end"`
Players []Player `bson:"players"`
}
type Player struct {
Name string `bson:"name"`
Decks [2]string `bson:"decks"`
Points uint8 `bson:"points"`
Place uint8 `bson:"place"`
}
func NewPlayer(name, firstDeck, secondDeck string, points, place uint8) Player {
return Player{
Name: name,
Decks: [2]string{firstDeck, secondDeck},
Points: points,
Place: place,
}
}
var isDropMe = true
func main() {
Host := []string{
"127.0.0.1:27017",
// replica set addrs...
}
const (
Username = "YOUR_USERNAME"
Password = "YOUR_PASS"
Database = "YOUR_DB"
Collection = "YOUR_COLLECTION"
)
session, err := mgo.DialWithInfo(&mgo.DialInfo{
Addrs: Host,
// Username: Username,
// Password: Password,
// Database: Database,
// DialServer: func(addr *mgo.ServerAddr) (net.Conn, error) {
// return tls.Dial("tcp", addr.String(), &tls.Config{})
// },
})
if err != nil {
panic(err)
}
defer session.Close()
game := Game{
Winner: "Dave",
OfficialGame: true,
Location: "Austin",
StartTime: time.Date(2015, time.February, 12, 04, 11, 0, 0, time.UTC),
EndTime: time.Now(),
Players: []Player{
NewPlayer("Dave", "Wizards", "Steampunk", 21, 1),
NewPlayer("Javier", "Zombies", "Ghosts", 18, 2),
NewPlayer("George", "Aliens", "Dinosaurs", 17, 3),
NewPlayer("Seth", "Spies", "Leprechauns", 10, 4),
},
}
if isDropMe {
err = session.DB("test").DropDatabase()
if err != nil {
panic(err)
}
}
// Collection
c := session.DB(Database).C(Collection)
// Insert
if err := c.Insert(game); err != nil {
panic(err)
}
// Find and Count
player := "Dave"
gamesWon, err := c.Find(bson.M{"winner": player}).Count()
if err != nil {
panic(err)
}
fmt.Printf("%s has won %d games.\n", player, gamesWon)
// Find One (with Projection)
var result Game
err = c.Find(bson.M{"winner": player, "location": "Austin"}).Select(bson.M{"official_game": 1}).One(&result)
if err != nil {
panic(err)
}
fmt.Println("Is game in Austin Official?", result.OfficialGame)
// Find All
var games []Game
err = c.Find(nil).Sort("-start").All(&games)
if err != nil {
panic(err)
}
fmt.Println("Number of Games", len(games))
// Update
newPlayer := "John"
selector := bson.M{"winner": player}
updator := bson.M{"$set": bson.M{"winner": newPlayer}}
if err := c.Update(selector, updator); err != nil {
panic(err)
}
// Update All
info, err := c.UpdateAll(selector, updator)
if err != nil {
panic(err)
}
fmt.Println("Updated", info.Updated)
// Remove
info, err = c.RemoveAll(bson.M{"winner": newPlayer})
if err != nil {
panic(err)
}
fmt.Println("Removed", info.Removed)
}