Implement singleton pattern for MongoDB instance (#214)

UTDNebula · Sep 16, 2024 · 911f7e2 · 911f7e2
1 parent d66e72f
commit 911f7e2
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Showing 7 changed files with 37 additions and 24 deletions.
diff --git a/api/configs/setup.go b/api/configs/setup.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"os"
 	"strconv"
+	"sync"
 	"time"
 
 	"github.com/UTDNebula/nebula-api/api/common/log"
@@ -14,34 +15,46 @@ import (
 	"go.mongodb.org/mongo-driver/mongo/options"
 )
 
+type DBSingleton struct {
+	client *mongo.Client
+}
+
+var dbInstance *DBSingleton
+var once sync.Once
+
 func ConnectDB() *mongo.Client {
+	once.Do(func() {
+		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		client, err := mongo.Connect(context.Background(), options.Client().ApplyURI(GetEnvMongoURI()))
+		if err != nil {
+			log.WriteErrorMsg("Unable to create MongoDB client")
+			os.Exit(1)
+		}
 
-	client, err := mongo.Connect(context.Background(), options.Client().ApplyURI(GetEnvMongoURI()))
-	if err != nil {
-		log.WriteErrorMsg("Unable to create MongoDB client")
-		os.Exit(1)
-	}
+		defer cancel()
 
-	defer cancel()
+		//ping the database
+		err = client.Ping(ctx, nil)
+		if err != nil {
+			log.WriteErrorMsg("Unable to ping database")
+			os.Exit(1)
+		}
 
-	//ping the database
-	err = client.Ping(ctx, nil)
-	if err != nil {
-		log.WriteErrorMsg("Unable to ping database")
-		os.Exit(1)
-	}
+		log.WriteDebug("Connected to MongoDB")
 
-	log.WriteDebug("Connected to MongoDB")
+		dbInstance = &DBSingleton{
+			client: client,
+		}
 
-	return client
-}
+	})
 
-var DB *mongo.Client = ConnectDB()
+	return dbInstance.client
+}
 
 // getting database collections
-func GetCollection(client *mongo.Client, collectionName string) *mongo.Collection {
+func GetCollection(collectionName string) *mongo.Collection {
+	client := ConnectDB()
 	collection := client.Database("combinedDB").Collection(collectionName)
 	return collection
 }

diff --git a/api/controllers/course.go b/api/controllers/course.go
@@ -17,7 +17,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
-var courseCollection *mongo.Collection = configs.GetCollection(configs.DB, "courses")
+var courseCollection *mongo.Collection = configs.GetCollection("courses")
 
 func CourseSearch() gin.HandlerFunc {
 	return func(c *gin.Context) {

diff --git a/api/controllers/degree.go b/api/controllers/degree.go
@@ -17,7 +17,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
-var degreeCollection *mongo.Collection = configs.GetCollection(configs.DB, "degrees")
+var degreeCollection *mongo.Collection = configs.GetCollection("degrees")
 
 func DegreeSearch() gin.HandlerFunc {
 	return func(c *gin.Context) {

diff --git a/api/controllers/evaluation.go b/api/controllers/evaluation.go
@@ -25,7 +25,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
-var evaluationCollection *mongo.Collection = configs.GetCollection(configs.DB, "evaluations")
+var evaluationCollection *mongo.Collection = configs.GetCollection("evaluations")
 
 func EvalBySectionID(c *gin.Context) {
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)

diff --git a/api/controllers/exam.go b/api/controllers/exam.go
@@ -18,7 +18,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
-var examCollection *mongo.Collection = configs.GetCollection(configs.DB, "exams")
+var examCollection *mongo.Collection = configs.GetCollection("exams")
 
 type examFilter struct {
 	Type  string `schema:"type"`

diff --git a/api/controllers/professor.go b/api/controllers/professor.go
@@ -17,7 +17,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
-var professorCollection *mongo.Collection = configs.GetCollection(configs.DB, "professors")
+var professorCollection *mongo.Collection = configs.GetCollection("professors")
 
 func ProfessorSearch() gin.HandlerFunc {
 	return func(c *gin.Context) {

diff --git a/api/controllers/section.go b/api/controllers/section.go
@@ -17,7 +17,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
-var sectionCollection *mongo.Collection = configs.GetCollection(configs.DB, "sections")
+var sectionCollection *mongo.Collection = configs.GetCollection("sections")
 
 func SectionSearch() gin.HandlerFunc {
 	return func(c *gin.Context) {