feat: add PostgreSQL, create follow relationships

Author: denysvitali

cmd/social-backend/main.go

@@ -13,7 +13,9 @@ var args struct {
 	ArangoUsername  string   `arg:"--arango-username,env:ARANGO_USERNAME"`
 	ArangoPassword  string   `arg:"--arango-password,env:ARANGO_PASSWORD"`
 	ArangoDatabase  string   `arg:"--arango-database,env:ARANGO_DATABASE"`
-	ListenAddr      string   `arg:"--listen-addr,env:LISTEN_ADDR"`
+	PostgresDSN     string   `arg:"--postgres-dsn,env:POSTGRESQL_DSN"`
+
+	ListenAddr string `arg:"--listen-addr,env:LISTEN_ADDR"`
 }
 
 var logger = logrus.New()
@@ -32,7 +34,8 @@ func main() {
 			Password:  args.ArangoPassword,
 			Database:  args.ArangoDatabase,
 		},
-		Logger: logger,
+		PostgresDSN: args.PostgresDSN,
+		Logger:      logger,
 	})
 
 	if err != nil {

docker-compose.yaml

@@ -8,5 +8,16 @@ services:
       - 8529:8529
     volumes:
       - arango-data:/var/lib/arangodb3
+  postgres:
+    image: 'postgres:15-alpine'
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_DB: social
+    ports:
+      - "5435:5432"
+    volumes:
+      - pgdata:/var/lib/postgresql/data
 volumes:
-  arango-data:
+  arango-data:
+  pgdata:

docs/architecture.md

@@ -0,0 +1,20 @@
+# Architecture
+
+## Database
+
+This project uses _two_ database engines. The reason of this choice is that we want
+the graph traversal speed of ArangoDB, but the schema enforcement of PostgreSQL (and all the other goodies of
+this DBMS).
+
+### ArangoDB
+
+ArangoDB is used to stored relationships that are likely to have a graph depth >= 2.  
+Such relationships are for example:
+
+- Follows / Followers relationships
+
+### PostgreSQL
+
+PostgreSQL contains everything else that doesn't need to be interacted with a graph traversal.
+For example, the followers relationship of a user will be stored in ArangoDB, whereas the user display name will
+be stored in PostgreSQL.

go.mod

@@ -17,6 +17,16 @@ require (
 	github.com/go-playground/universal-translator v0.18.0 // indirect
 	github.com/go-playground/validator/v10 v10.11.1 // indirect
 	github.com/goccy/go-json v0.9.11 // indirect
+	github.com/jackc/chunkreader/v2 v2.0.1 // indirect
+	github.com/jackc/pgconn v1.13.0 // indirect
+	github.com/jackc/pgio v1.0.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgproto3/v2 v2.3.1 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20200714003250-2b9c44734f2b // indirect
+	github.com/jackc/pgtype v1.12.0 // indirect
+	github.com/jackc/pgx/v4 v4.17.2 // indirect
+	github.com/jinzhu/inflection v1.0.0 // indirect
+	github.com/jinzhu/now v1.1.5 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/leodido/go-urn v1.2.1 // indirect
 	github.com/mattn/go-isatty v0.0.16 // indirect
@@ -31,4 +41,6 @@ require (
 	golang.org/x/text v0.4.0 // indirect
 	google.golang.org/protobuf v1.28.1 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
+	gorm.io/driver/postgres v1.4.5 // indirect
+	gorm.io/gorm v1.24.1-0.20221019064659-5dd2bb482755 // indirect
 )

go.sum

@@ -2,19 +2,24 @@ package server
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"github.com/arangodb/go-driver"
-	"github.com/denysvitali/social/backend/pkg/models"
+	"github.com/denysvitali/social/backend/pkg/models/arango"
+	pg_model "github.com/denysvitali/social/backend/pkg/models/postgres"
 	v1requests "github.com/denysvitali/social/backend/pkg/requests/v1"
 	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
 	"net/http"
 )
 
 func (s *Server) initAPIv1(g *gin.RouterGroup) {
-	g.GET("/users/by_username/:username", s.apiV1UserByUsername)
-	g.GET("/users/:id", s.apiV1Users)
 	g.POST("/users", s.apiV1CreateUser)
+	g.GET("/users/:id", s.apiV1Users)
+	g.GET("/users/by-username/:username", s.apiV1UserByUsername)
 	g.POST("/users/:id/follows/:target_id", s.apiV1SetUserFollows)
+
+	g.GET("/posts/:id", s.apiV1PostById)
 }
 
 func (s *Server) apiV1Users(c *gin.Context) {
@@ -56,6 +61,24 @@ func (s *Server) apiV1UserByUsername(c *gin.Context) {
 		)
 		return
 	}
+
+	var user pg_model.User
+	tx := s.pgDB.First(&user, "username = ?", usernameKey)
+	if tx.Error != nil {
+		if errors.Is(tx.Error, gorm.ErrRecordNotFound) {
+			s.notFound(c, "user not found")
+			return
+		}
+		s.internalServerError(c, "unable to get user by username: %v", tx.Error)
+		return
+	}
+
+	if user.Deleted {
+		s.notFound(c, "user doesn't exist anymore")
+		return
+	}
+
+	c.JSON(http.StatusOK, user)
 }
 
 func (s *Server) apiV1SetUserFollows(c *gin.Context) {
@@ -164,7 +187,7 @@ func (s *Server) apiV1CreateUser(c *gin.Context) {
 		return
 	}
 
-	meta, err := coll.CreateDocument(ctx, models.User{
+	meta, err := coll.CreateDocument(ctx, arango.User{
 		Username:  req.Username,
 		FirstName: req.FirstName,
 		LastName:  req.LastName,

pkg/api_v1.go

@@ -0,0 +1,30 @@
+package server
+
+import (
+	"errors"
+	pgmodel "github.com/denysvitali/social/backend/pkg/models/postgres"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+	"net/http"
+)
+
+func (s *Server) apiV1PostById(c *gin.Context) {
+	id := c.Param("id")
+	if id == "" {
+		s.badRequest(c, "id is empty", "id cannot be empty")
+		return
+	}
+
+	var p pgmodel.Post
+	tx := s.pgDB.Preload("Author").First(&p, "id = ?", id)
+	if tx.Error != nil {
+		if errors.Is(tx.Error, gorm.ErrRecordNotFound) {
+			s.notFound(c, "post not found")
+			return
+		}
+		s.internalServerError(c, "unable to get post with id %s: %v", id, tx.Error)
+		return
+	}
+
+	c.JSON(http.StatusOK, p)
+}

pkg/api_v1_posts.go

@@ -1,4 +1,4 @@
-package models
+package arango
 
 type User struct {
 	Username  string `json:"username"`

pkg/models/user.go renamed to pkg/models/arango/user.go

@@ -0,0 +1,19 @@
+package pg_model
+
+import "time"
+
+type Post struct {
+	ID        uint64    `gorm:"primaryKey" json:"id"`
+	CreatedAt time.Time `json:"createdAt"`
+	Content   string    `json:"content"`
+
+	ParentPost   *Post  `json:"parentPost,omitempty"`
+	ParentPostID uint64 `json:"parentPostID,omitempty"`
+
+	ReshareCount uint32 `json:"reshareCount"`
+	ReplyCount   uint32 `json:"replyCount"`
+
+	Author   *User  `json:"author,omitempty"`
+	AuthorID uint64 `json:"authorId"`
+	Deleted  bool   `json:"-"`
+}

pkg/models/postgres/post.go

@@ -0,0 +1,19 @@
+package pg_model
+
+import "time"
+
+type User struct {
+	ID             uint64    `gorm:"primaryKey" json:"id"`
+	CreatedAt      time.Time `json:"createdAt"`
+	Username       string    `gorm:"index" json:"username"`
+	DisplayName    string    `json:"displayName"`
+	Biography      string    `json:"biography"`
+	Location       string    `json:"location"`
+	FollowersCount int       `json:"followersCount"`
+	FollowingCount int       `json:"followingCount"`
+	Verified       bool      `json:"verified"`
+	Deleted        bool      `json:"-"`
+
+	// HasMany relations
+	Posts []Post `gorm:"foreignKey:AuthorID" json:"posts,omitempty"`
+}

pkg/models/postgres/user.go

@@ -5,8 +5,11 @@ import (
 	"fmt"
 	"github.com/arangodb/go-driver"
 	arangohttp "github.com/arangodb/go-driver/http"
+	pg_model "github.com/denysvitali/social/backend/pkg/models/postgres"
 	"github.com/gin-gonic/gin"
 	"github.com/sirupsen/logrus"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
 )
 
 type Server struct {
@@ -15,6 +18,7 @@ type Server struct {
 
 	graphConn driver.Client
 	graphDb   driver.Database
+	pgDB      *gorm.DB
 }
 
 type ArangoConfig struct {
@@ -26,18 +30,53 @@ type ArangoConfig struct {
 }
 
 type Config struct {
-	Arango ArangoConfig
+	Arango      ArangoConfig
+	PostgresDSN string
+
 	Logger *logrus.Logger
 }
 
 func New(config Config) (*Server, error) {
+	if config.Logger == nil {
+		config.Logger = logrus.New()
+		config.Logger.Warnf("nil logger passed in config, creating a new logger")
+	}
+
+	c, db, err := setupArango(config)
+	if err != nil {
+		return nil, fmt.Errorf("unable to set-up ArangoDB")
+	}
+
+	pgdb, err := setupPostgres(config)
+	if err != nil {
+		return nil, fmt.Errorf("unable to set-up PostgreSQL")
+	}
+
+	s := Server{
+		e:         gin.New(),
+		graphConn: c,
+		graphDb:   db,
+		pgDB:      pgdb,
+		logger:    config.Logger,
+	}
+
+	s.init()
+
+	return &s, nil
+}
+
+func setupPostgres(config Config) (*gorm.DB, error) {
+	return gorm.Open(postgres.Open(config.PostgresDSN), &gorm.Config{})
+}
+
+func setupArango(config Config) (driver.Client, driver.Database, error) {
 	conn, err := arangohttp.NewConnection(
 		arangohttp.ConnectionConfig{
 			Endpoints: config.Arango.Endpoints,
 		},
 	)
 	if err != nil {
-		return nil, fmt.Errorf("unable to create arango HTTP connection: %v", err)
+		return nil, nil, fmt.Errorf("unable to create arango HTTP connection: %v", err)
 	}
 
 	c, err := driver.NewClient(driver.ClientConfig{
@@ -49,36 +88,36 @@ func New(config Config) (*Server, error) {
 		SynchronizeEndpointsInterval: 0,
 	})
 	if err != nil {
-		return nil, fmt.Errorf("unable to create ArangoDB client: %v", err)
-	}
-
-	if config.Logger == nil {
-		config.Logger = logrus.New()
-		config.Logger.Warnf("nil logger passed in config, creating a new logger")
+		return nil, nil, fmt.Errorf("unable to create ArangoDB client: %v", err)
 	}
 
 	db, err := c.Database(context.TODO(), config.Arango.Database)
 	if err != nil {
-		return nil, fmt.Errorf("unable to get ArangoDB database: %v", err)
+		return nil, nil, fmt.Errorf("unable to get ArangoDB database: %v", err)
 	}
-
-	s := Server{
-		e:         gin.New(),
-		graphConn: c,
-		graphDb:   db,
-		logger:    config.Logger,
-	}
-
-	s.init()
-
-	return &s, nil
+	return c, db, nil
 }
 
 func (s *Server) Listen(addr ...string) error {
 	return s.e.Run(addr...)
 }
 
 func (s *Server) init() {
+	// init db
+	s.initPostgreSQL()
+
 	g := s.e.Group("/api/v1")
 	s.initAPIv1(g)
 }
+
+func (s *Server) initPostgreSQL() {
+	for _, v := range []any{
+		&pg_model.User{},
+		&pg_model.Post{},
+	} {
+		err := s.pgDB.AutoMigrate(v)
+		if err != nil {
+			s.logger.Errorf("unable to automigrate %t: %v", v, err)
+		}
+	}
+}