Fix parallel creating commit status bug with tests (#21911) (#21989)

backport #21911 
backport #21998

Co-authored-by: silverwind <me@silverwind.io>

2 files changed, 70 insertions, 65 deletions

diff --git a/models/db/index.go b/models/db/index.go
index 58a976ad52..f64bf6bfb5 100644
--- a/models/db/index.go
+++ b/models/db/index.go
@@ -8,6 +8,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"strconv"
+
+	"code.gitea.io/gitea/modules/setting"
 )
 
 // ResourceIndex represents a resource index which could be used as issue/release and others
@@ -24,11 +27,6 @@ var (
 	ErrGetResourceIndexFailed = errors.New("get resource index failed")
 )
 
-const (
-	// MaxDupIndexAttempts max retry times to create index
-	MaxDupIndexAttempts = 3
-)
-
 // SyncMaxResourceIndex sync the max index with the resource
 func SyncMaxResourceIndex(ctx context.Context, tableName string, groupID, maxIndex int64) (err error) {
 	e := GetEngine(ctx)
@@ -61,8 +59,25 @@ func SyncMaxResourceIndex(ctx context.Context, tableName string, groupID, maxInd
 	return nil
 }
 
+func postgresGetNextResourceIndex(ctx context.Context, tableName string, groupID int64) (int64, error) {
+	res, err := GetEngine(ctx).Query(fmt.Sprintf("INSERT INTO %s (group_id, max_index) "+
+		"VALUES (?,1) ON CONFLICT (group_id) DO UPDATE SET max_index = %s.max_index+1 RETURNING max_index",
+		tableName, tableName), groupID)
+	if err != nil {
+		return 0, err
+	}
+	if len(res) == 0 {
+		return 0, ErrGetResourceIndexFailed
+	}
+	return strconv.ParseInt(string(res[0]["max_index"]), 10, 64)
+}
+
 // GetNextResourceIndex generates a resource index, it must run in the same transaction where the resource is created
 func GetNextResourceIndex(ctx context.Context, tableName string, groupID int64) (int64, error) {
+	if setting.Database.UsePostgreSQL {
+		return postgresGetNextResourceIndex(ctx, tableName, groupID)
+	}
+
 	e := GetEngine(ctx)
 
 	// try to update the max_index to next value, and acquire the write-lock for the record
diff --git a/models/git/commit_status.go b/models/git/commit_status.go
index 620baa036c..53c5458040 100644
--- a/models/git/commit_status.go
+++ b/models/git/commit_status.go
@@ -7,8 +7,10 @@ package git
 import (
 	"context"
 	"crypto/sha1"
+	"errors"
 	"fmt"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -49,79 +51,67 @@ func init() {
 	db.RegisterModel(new(CommitStatusIndex))
 }
 
-// upsertCommitStatusIndex the function will not return until it acquires the lock or receives an error.
-func upsertCommitStatusIndex(ctx context.Context, repoID int64, sha string) (err error) {
-	// An atomic UPSERT operation (INSERT/UPDATE) is the only operation
-	// that ensures that the key is actually locked.
-	switch {
-	case setting.Database.UseSQLite3 || setting.Database.UsePostgreSQL:
-		_, err = db.Exec(ctx, "INSERT INTO `commit_status_index` (repo_id, sha, max_index) "+
-			"VALUES (?,?,1) ON CONFLICT (repo_id,sha) DO UPDATE SET max_index = `commit_status_index`.max_index+1",
-			repoID, sha)
-	case setting.Database.UseMySQL:
-		_, err = db.Exec(ctx, "INSERT INTO `commit_status_index` (repo_id, sha, max_index) "+
-			"VALUES (?,?,1) ON DUPLICATE KEY UPDATE max_index = max_index+1",
-			repoID, sha)
-	case setting.Database.UseMSSQL:
-		// https://weblogs.sqlteam.com/dang/2009/01/31/upsert-race-condition-with-merge/
-		_, err = db.Exec(ctx, "MERGE `commit_status_index` WITH (HOLDLOCK) as target "+
-			"USING (SELECT ? AS repo_id, ? AS sha) AS src "+
-			"ON src.repo_id = target.repo_id AND src.sha = target.sha "+
-			"WHEN MATCHED THEN UPDATE SET target.max_index = target.max_index+1 "+
-			"WHEN NOT MATCHED THEN INSERT (repo_id, sha, max_index) "+
-			"VALUES (src.repo_id, src.sha, 1);",
-			repoID, sha)
-	default:
-		return fmt.Errorf("database type not supported")
+func postgresGetCommitStatusIndex(ctx context.Context, repoID int64, sha string) (int64, error) {
+	res, err := db.GetEngine(ctx).Query("INSERT INTO `commit_status_index` (repo_id, sha, max_index) "+
+		"VALUES (?,?,1) ON CONFLICT (repo_id, sha) DO UPDATE SET max_index = `commit_status_index`.max_index+1 RETURNING max_index",
+		repoID, sha)
+	if err != nil {
+		return 0, err
+	}
+	if len(res) == 0 {
+		return 0, db.ErrGetResourceIndexFailed
 	}
-	return err
+	return strconv.ParseInt(string(res[0]["max_index"]), 10, 64)
 }
 
 // GetNextCommitStatusIndex retried 3 times to generate a resource index
-func GetNextCommitStatusIndex(repoID int64, sha string) (int64, error) {
-	for i := 0; i < db.MaxDupIndexAttempts; i++ {
-		idx, err := getNextCommitStatusIndex(repoID, sha)
-		if err == db.ErrResouceOutdated {
-			continue
-		}
-		if err != nil {
-			return 0, err
-		}
-		return idx, nil
+func GetNextCommitStatusIndex(ctx context.Context, repoID int64, sha string) (int64, error) {
+	if setting.Database.UsePostgreSQL {
+		return postgresGetCommitStatusIndex(ctx, repoID, sha)
 	}
-	return 0, db.ErrGetResourceIndexFailed
-}
 
-// getNextCommitStatusIndex return the next index
-func getNextCommitStatusIndex(repoID int64, sha string) (int64, error) {
-	ctx, commiter, err := db.TxContext()
+	e := db.GetEngine(ctx)
+
+	// try to update the max_index to next value, and acquire the write-lock for the record
+	res, err := e.Exec("UPDATE `commit_status_index` SET max_index=max_index+1 WHERE repo_id=? AND sha=?", repoID, sha)
 	if err != nil {
 		return 0, err
 	}
-	defer commiter.Close()
-
-	var preIdx int64
-	_, err = db.GetEngine(ctx).SQL("SELECT max_index FROM `commit_status_index` WHERE repo_id = ? AND sha = ?", repoID, sha).Get(&preIdx)
+	affected, err := res.RowsAffected()
 	if err != nil {
 		return 0, err
 	}
+	if affected == 0 {
+		// this slow path is only for the first time of creating a resource index
+		_, errIns := e.Exec("INSERT INTO `commit_status_index` (repo_id, sha, max_index) VALUES (?, ?, 0)", repoID, sha)
+		res, err = e.Exec("UPDATE `commit_status_index` SET max_index=max_index+1 WHERE repo_id=? AND sha=?", repoID, sha)
+		if err != nil {
+			return 0, err
+		}
 
-	if err := upsertCommitStatusIndex(ctx, repoID, sha); err != nil {
-		return 0, err
+		affected, err = res.RowsAffected()
+		if err != nil {
+			return 0, err
+		}
+		// if the update still can not update any records, the record must not exist and there must be some errors (insert error)
+		if affected == 0 {
+			if errIns == nil {
+				return 0, errors.New("impossible error when GetNextCommitStatusIndex, insert and update both succeeded but no record is updated")
+			}
+			return 0, errIns
+		}
 	}
 
-	var curIdx int64
-	has, err := db.GetEngine(ctx).SQL("SELECT max_index FROM `commit_status_index` WHERE repo_id = ? AND sha = ? AND max_index=?", repoID, sha, preIdx+1).Get(&curIdx)
+	// now, the new index is in database (protected by the transaction and write-lock)
+	var newIdx int64
+	has, err := e.SQL("SELECT max_index FROM `commit_status_index` WHERE repo_id=? AND sha=?", repoID, sha).Get(&newIdx)
 	if err != nil {
 		return 0, err
 	}
 	if !has {
-		return 0, db.ErrResouceOutdated
-	}
-	if err := commiter.Commit(); err != nil {
-		return 0, err
+		return 0, errors.New("impossible error when GetNextCommitStatusIndex, upsert succeeded but no record can be selected")
 	}
-	return curIdx, nil
+	return newIdx, nil
 }
 
 func (status *CommitStatus) loadAttributes(ctx context.Context) (err error) {
@@ -291,18 +281,18 @@ func NewCommitStatus(opts NewCommitStatusOptions) error {
 		return fmt.Errorf("NewCommitStatus[%s, %s]: no user specified", repoPath, opts.SHA)
 	}
 
-	// Get the next Status Index
-	idx, err := GetNextCommitStatusIndex(opts.Repo.ID, opts.SHA)
-	if err != nil {
-		return fmt.Errorf("generate commit status index failed: %w", err)
-	}
-
 	ctx, committer, err := db.TxContext()
 	if err != nil {
 		return fmt.Errorf("NewCommitStatus[repo_id: %d, user_id: %d, sha: %s]: %w", opts.Repo.ID, opts.Creator.ID, opts.SHA, err)
 	}
 	defer committer.Close()
 
+	// Get the next Status Index
+	idx, err := GetNextCommitStatusIndex(ctx, opts.Repo.ID, opts.SHA)
+	if err != nil {
+		return fmt.Errorf("generate commit status index failed: %w", err)
+	}
+
 	opts.CommitStatus.Description = strings.TrimSpace(opts.CommitStatus.Description)
 	opts.CommitStatus.Context = strings.TrimSpace(opts.CommitStatus.Context)
 	opts.CommitStatus.TargetURL = strings.TrimSpace(opts.CommitStatus.TargetURL)
@@ -316,7 +306,7 @@ func NewCommitStatus(opts NewCommitStatusOptions) error {
 
 	// Insert new CommitStatus
 	if _, err = db.GetEngine(ctx).Insert(opts.CommitStatus); err != nil {
-		return fmt.Errorf("Insert CommitStatus[%s, %s]: %w", repoPath, opts.SHA, err)
+		return fmt.Errorf("insert CommitStatus[%s, %s]: %w", repoPath, opts.SHA, err)
 	}
 
 	return committer.Commit()