Add cache for branch divergence on branch list page (#29577)

The branch page for blender project will take 6s because calculating
divergence is very slow.
This PR will add a cache for the branch divergence calculation. So when
the second visit the branch list, it will take only less 200ms.

2 files changed, 54 insertions, 6 deletions

diff --git a/services/repository/branch.go b/services/repository/branch.go
index 763fb966c5..8d8cfa2d19 100644
--- a/services/repository/branch.go
+++ b/services/repository/branch.go
@@ -16,9 +16,11 @@ import (
 	issues_model "code.gitea.io/gitea/models/issues"
 	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/gitrepo"
 	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/queue"
@@ -99,7 +101,6 @@ func LoadBranches(ctx context.Context, repo *repo_model.Repository, gitRepo *git
 		if err != nil {
 			return nil, nil, 0, fmt.Errorf("loadOneBranch: %v", err)
 		}
-
 		branches = append(branches, branch)
 	}
 
@@ -109,10 +110,44 @@ func LoadBranches(ctx context.Context, repo *repo_model.Repository, gitRepo *git
 	if err != nil {
 		return nil, nil, 0, fmt.Errorf("loadOneBranch: %v", err)
 	}
-
 	return defaultBranch, branches, totalNumOfBranches, nil
 }
 
+func getDivergenceCacheKey(repoID int64, branchName string) string {
+	return fmt.Sprintf("%d-%s", repoID, branchName)
+}
+
+// getDivergenceFromCache gets the divergence from cache
+func getDivergenceFromCache(repoID int64, branchName string) (*git.DivergeObject, bool) {
+	data := cache.GetCache().Get(getDivergenceCacheKey(repoID, branchName))
+	res := git.DivergeObject{
+		Ahead:  -1,
+		Behind: -1,
+	}
+	s, ok := data.([]byte)
+	if !ok || len(s) == 0 {
+		return &res, false
+	}
+
+	if err := json.Unmarshal(s, &res); err != nil {
+		log.Error("json.UnMarshal failed: %v", err)
+		return &res, false
+	}
+	return &res, true
+}
+
+func putDivergenceFromCache(repoID int64, branchName string, divergence *git.DivergeObject) error {
+	bs, err := json.Marshal(divergence)
+	if err != nil {
+		return err
+	}
+	return cache.GetCache().Put(getDivergenceCacheKey(repoID, branchName), bs, 30*24*60*60)
+}
+
+func DelDivergenceFromCache(repoID int64, branchName string) error {
+	return cache.GetCache().Delete(getDivergenceCacheKey(repoID, branchName))
+}
+
 func loadOneBranch(ctx context.Context, repo *repo_model.Repository, dbBranch *git_model.Branch, protectedBranches *git_model.ProtectedBranchRules,
 	repoIDToRepo map[int64]*repo_model.Repository,
 	repoIDToGitRepo map[int64]*git.Repository,
@@ -130,10 +165,18 @@ func loadOneBranch(ctx context.Context, repo *repo_model.Repository, dbBranch *g
 
 	// it's not default branch
 	if repo.DefaultBranch != dbBranch.Name && !dbBranch.IsDeleted {
-		var err error
-		divergence, err = files_service.CountDivergingCommits(ctx, repo, git.BranchPrefix+branchName)
-		if err != nil {
-			log.Error("CountDivergingCommits: %v", err)
+		var cached bool
+		divergence, cached = getDivergenceFromCache(repo.ID, dbBranch.Name)
+		if !cached {
+			var err error
+			divergence, err = files_service.CountDivergingCommits(ctx, repo, git.BranchPrefix+branchName)
+			if err != nil {
+				log.Error("CountDivergingCommits: %v", err)
+			} else {
+				if err = putDivergenceFromCache(repo.ID, dbBranch.Name, divergence); err != nil {
+					log.Error("putDivergenceFromCache: %v", err)
+				}
+			}
 		}
 	}
 
diff --git a/services/repository/push.go b/services/repository/push.go
index 0aeb4c830b..39843249a5 100644
--- a/services/repository/push.go
+++ b/services/repository/push.go
@@ -220,6 +220,11 @@ func pushUpdates(optsList []*repo_module.PushUpdateOptions) error {
 					}
 				}
 
+				// delete cache for divergence
+				if err := DelDivergenceFromCache(repo.ID, branch); err != nil {
+					log.Error("DelDivergenceFromCache: %v", err)
+				}
+
 				commits := repo_module.GitToPushCommits(l)
 				commits.HeadCommit = repo_module.CommitToPushCommit(newCommit)