如何在 Go 中重用 MongoDB 连接

Question

我想将用 Go 编写的服务器与 MongoDB 连接，但我不确定如何以有效的方式进行连接。我发现有几个例子实现了它，如下所示。

库/mongodb/client.go

package mongodb

import (
    "context"
    "log"
    "project/keys"

    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func GetClient() *mongo.Database {
    client, err := mongo.Connect(
        context.Background(),
        options.Client().ApplyURI(keys.GetKeys().MONGO_URI),
    )

    if err != nil {
        log.Fatal(err)
    }

    return client.Database(keys.GetKeys().MONGO_DB_NAME)
}

服务/用户/findOne.go

package userservices

import (
    "context"
    "log"
    "project/libs/mongodb"
    "project/models"

    "go.mongodb.org/mongo-driver/bson"
)

func FindOne(filter bson.M) (models.User, error) {
    var user models.User

    collection := mongodb.GetClient().Collection("users")
    result := collection.FindOne(context.TODO(), filter)

    if result.Err() != nil {
        return user, result.Err()
    }

    if err := result.Decode(&user); err != nil {
        log.Println("Failed to decode user with error:", err)
        return user, err
    }

    return user, nil
}

该GetClient函数返回一个数据库实例，然后在整个应用程序中使用该实例。这似乎有效，但我想知道这是否真的是最佳实践，因为它似乎在每次请求新客户端时都创建一个新连接，如第二个代码片段所示，还是该假设不正确？我还考虑转换GetClient为单例，它总是返回相同的数据库实例，但在这种情况下如何处理丢失的连接？谢谢

Answer 1

我这样做。在服务启动时执行一次，然后将 MongoDatastore 对象传递给编排器、服务层和存储库层。我正在为 mongo 使用“github.com/mongodb/mongo-go-driver/mongo”驱动程序。我认为它在内部监视和回收空闲连接。因此，只要不丢失对 mongo.Client 对象的引用，我们就不必担心断开的连接。

const CONNECTED = "Successfully connected to database: %v"

type MongoDatastore struct {
    db      *mongo.Database
    Session *mongo.Client
    logger  *logrus.Logger
}

func NewDatastore(config config.GeneralConfig, logger *logrus.Logger) *MongoDatastore {

    var mongoDataStore *MongoDatastore
    db, session := connect(config, logger)
    if db != nil && session != nil {

        // log statements here as well

        mongoDataStore = new(MongoDatastore)
        mongoDataStore.db = db
        mongoDataStore.logger = logger
        mongoDataStore.Session = session
        return mongoDataStore
    }

    logger.Fatalf("Failed to connect to database: %v", config.DatabaseName)

    return nil
}

func connect(generalConfig config.GeneralConfig, logger *logrus.Logger) (a *mongo.Database, b *mongo.Client) {
    var connectOnce sync.Once
    var db *mongo.Database
    var session *mongo.Client
    connectOnce.Do(func() {
        db, session = connectToMongo(generalConfig, logger)
    })

    return db, session
}

func connectToMongo(generalConfig config.GeneralConfig, logger *logrus.Logger) (a *mongo.Database, b *mongo.Client) {

    var err error
    session, err := mongo.NewClient(generalConfig.DatabaseHost)
    if err != nil {
        logger.Fatal(err)
    }
    session.Connect(context.TODO())
    if err != nil {
        logger.Fatal(err)
    }

    var DB = session.Database(generalConfig.DatabaseName)
    logger.Info(CONNECTED, generalConfig.DatabaseName)

    return DB, session
}

您现在可以创建您的存储库，如下所示：-

type TestRepository interface{
    Find(ctx context.Context, filters interface{}) []Document, error
}

type testRepository struct {
    store      *datastore.MongoDatastore
}

func (r *testRepository) Find(ctx context.Context , filters interface{}) []Document, error{
    cur, err := r.store.GetCollection("some_collection_name").Find(ctx, filters)
    if err != nil {
        return nil, err
    }
    defer cur.Close(ctx)
    var result = make([]models.Document, 0)
    for cur.Next(ctx) {
        var currDoc models.Document
        err := cur.Decode(&currDoc)
        if err != nil {
            //log here
            continue
        }
        result = append(result, currDoc)
    }
    return result, err
}