From a8a948adf1413bca1281780c2002b2f2e8a0ecbe Mon Sep 17 00:00:00 2001
From: Joscha Henningsen <44805696+joschahenningsen@users.noreply.github.com>
Date: Wed, 30 Oct 2024 22:47:45 +0100
Subject: [PATCH] implement simple cache for news (#459)

* implement simple cache for news

* improve cache key method name

* use lru for cache

* cleanup

* remove previous cache
---
 server/backend/news.go | 78 ++++++++++++++++++++++++++++--------------
 server/go.mod          |  1 +
 server/go.sum          |  2 ++
 3 files changed, 56 insertions(+), 25 deletions(-)

diff --git a/server/backend/news.go b/server/backend/news.go
index 158a14a3..c83e3434 100644
--- a/server/backend/news.go
+++ b/server/backend/news.go
@@ -4,28 +4,28 @@ import (
 	"context"
 	"errors"
 	"fmt"
-
-	"gorm.io/gorm"
-
-	"google.golang.org/protobuf/types/known/timestamppb"
+	"time"
 
 	pb "github.com/TUM-Dev/Campus-Backend/server/api/tumdev"
 	"github.com/TUM-Dev/Campus-Backend/server/model"
+	"github.com/hashicorp/golang-lru/v2/expirable"
 	log "github.com/sirupsen/logrus"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/types/known/timestamppb"
+	"gorm.io/gorm"
 )
 
+var newsSourceCache = expirable.NewLRU[string, []model.NewsSource](1, nil, time.Hour*6)
+var newsCache = expirable.NewLRU[string, []model.News](1024, nil, time.Minute*30)
+
 func (s *CampusServer) ListNewsSources(ctx context.Context, _ *pb.ListNewsSourcesRequest) (*pb.ListNewsSourcesReply, error) {
 	if err := s.checkDevice(ctx); err != nil {
 		return nil, err
 	}
 
-	var sources []model.NewsSource
-	if err := s.db.WithContext(ctx).
-		Joins("File").
-		Find(&sources).Error; err != nil {
-		log.WithError(err).Error("could not find news_sources")
+	sources, err := s.getNewsSources(ctx)
+	if err != nil {
 		return nil, status.Error(codes.Internal, "could not ListNewsSources")
 	}
 
@@ -40,27 +40,27 @@ func (s *CampusServer) ListNewsSources(ctx context.Context, _ *pb.ListNewsSource
 	return &pb.ListNewsSourcesReply{Sources: resp}, nil
 }
 
+const CacheKeyAllNewsSources = "all_news_sources"
+
+func (s *CampusServer) getNewsSources(ctx context.Context) ([]model.NewsSource, error) {
+	if newsSources, ok := newsSourceCache.Get(CacheKeyAllNewsSources); ok {
+		return newsSources, nil
+	}
+	var sources []model.NewsSource
+	if err := s.db.WithContext(ctx).Joins("File").Find(&sources).Error; err != nil {
+		return nil, err
+	}
+	newsSourceCache.Add(CacheKeyAllNewsSources, sources)
+	return sources, nil
+}
+
 func (s *CampusServer) ListNews(ctx context.Context, req *pb.ListNewsRequest) (*pb.ListNewsReply, error) {
 	if err := s.checkDevice(ctx); err != nil {
 		return nil, err
 	}
 
-	var newsEntries []model.News
-	tx := s.db.WithContext(ctx).
-		Joins("File").
-		Joins("NewsSource").
-		Joins("NewsSource.File")
-	if req.NewsSource != 0 {
-		tx = tx.Where("src = ?", req.NewsSource)
-	}
-	if req.OldestDateAt.GetSeconds() != 0 || req.OldestDateAt.GetNanos() != 0 {
-		tx = tx.Where("date > ?", req.OldestDateAt.AsTime())
-	}
-	if req.LastNewsId != 0 {
-		tx = tx.Where("news > ?", req.LastNewsId)
-	}
-	if err := tx.Find(&newsEntries).Error; err != nil {
-		log.WithError(err).Error("could not find news item")
+	var newsEntries, err = s.getNews(ctx, req.NewsSource, req.LastNewsId, req.OldestDateAt.AsTime())
+	if err != nil {
 		return nil, status.Error(codes.Internal, "could not ListNews")
 	}
 
@@ -86,6 +86,34 @@ func (s *CampusServer) ListNews(ctx context.Context, req *pb.ListNewsRequest) (*
 	return &pb.ListNewsReply{News: resp}, nil
 }
 
+func (s *CampusServer) getNews(ctx context.Context, sourceID int32, lastNewsID int32, oldestDateAt time.Time) ([]model.News, error) {
+	cacheKey := fmt.Sprintf("%d_%d_%d", sourceID, oldestDateAt.Second(), lastNewsID)
+
+	if news, ok := newsCache.Get(cacheKey); ok {
+		return news, nil
+	}
+
+	var news []model.News
+	tx := s.db.WithContext(ctx).
+		Joins("File").
+		Joins("NewsSource").
+		Joins("NewsSource.File")
+	if sourceID != 0 {
+		tx = tx.Where("src = ?", sourceID)
+	}
+	if oldestDateAt.Second() != 0 || oldestDateAt.Nanosecond() != 0 {
+		tx = tx.Where("date > ?", oldestDateAt)
+	}
+	if lastNewsID != 0 {
+		tx = tx.Where("news > ?", lastNewsID)
+	}
+	if err := tx.Find(&news).Error; err != nil {
+		return nil, err
+	}
+	newsCache.Add(cacheKey, news)
+	return news, nil
+}
+
 func (s *CampusServer) ListNewsAlerts(ctx context.Context, req *pb.ListNewsAlertsRequest) (*pb.ListNewsAlertsReply, error) {
 	if err := s.checkDevice(ctx); err != nil {
 		return nil, err
diff --git a/server/go.mod b/server/go.mod
index ed963c3f..820152a1 100644
--- a/server/go.mod
+++ b/server/go.mod
@@ -58,6 +58,7 @@ require (
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/gorilla/css v1.0.1 // indirect
+	github.com/hashicorp/golang-lru/v2 v2.0.7 // 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
diff --git a/server/go.sum b/server/go.sum
index 7b2b5859..9266c693 100644
--- a/server/go.sum
+++ b/server/go.sum
@@ -157,6 +157,8 @@ github.com/grpc-ecosystem/grpc-gateway/v2 v2.22.0 h1:asbCHRVmodnJTuQ3qamDwqVOIjw
 github.com/grpc-ecosystem/grpc-gateway/v2 v2.22.0/go.mod h1:ggCgvZ2r7uOoQjOyu2Y1NhHmEPPzzuhWgcza5M1Ji1I=
 github.com/guregu/null v4.0.0+incompatible h1:4zw0ckM7ECd6FNNddc3Fu4aty9nTlpkkzH7dPn4/4Gw=
 github.com/guregu/null v4.0.0+incompatible/go.mod h1:ePGpQaN9cw0tj45IR5E5ehMvsFlLlQZAkkOXZurJ3NM=
+github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
+github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/ianlancetaylor/demangle v0.0.0-20200824232613-28f6c0f3b639/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=