WIP: By-repository mutex to create issues

go.mod

@@ -105,6 +105,7 @@ require (
 	github.com/urfave/cli v1.20.0
 	github.com/willf/bitset v0.0.0-20180426185212-8ce1146b8621 // indirect
 	github.com/yohcop/openid-go v0.0.0-20160914080427-2c050d2dae53
+	go.chromium.org/luci v0.0.0-20190816194131-4b600c9efb12
 	go.etcd.io/bbolt v1.3.2 // indirect
 	golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4
 	golang.org/x/net v0.0.0-20190724013045-ca1201d0de80

go.sum

@@ -367,6 +367,8 @@ github.com/yohcop/openid-go v0.0.0-20160914080427-2c050d2dae53 h1:HsIQ6yAjfjQ3Ix
 github.com/yohcop/openid-go v0.0.0-20160914080427-2c050d2dae53/go.mod h1:f6elajwZV+xceiaqgRL090YzLEDGSbqr3poGL3ZgXYo=
 github.com/ziutek/mymysql v1.5.4 h1:GB0qdRGsTwQSBVYuVShFBKaXSnSnYYC2d9knnE1LHFs=
 github.com/ziutek/mymysql v1.5.4/go.mod h1:LMSpPZ6DbqWFxNCHW77HeMg9I646SAhApZ/wKdgO/C0=
+go.chromium.org/luci v0.0.0-20190816194131-4b600c9efb12 h1:mY6O4bEXDOKJNhqkv17p5Pxjk3hM9RoRPeMc2CJWM2A=
+go.chromium.org/luci v0.0.0-20190816194131-4b600c9efb12/go.mod h1:MIQewVTLvOvc0UioV0JNqTNO/RspKFS0XEeoKrOxsdM=
 go.etcd.io/bbolt v1.3.2 h1:Z/90sZLPOeCy2PwprqkFa25PdkusRzaj9P8zm/KNyvk=
 go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.opencensus.io v0.20.1/go.mod h1:6WKK9ahsWS3RSO+PY9ZHZUfv2irvY6gN279GOPZjmmk=

models/issue.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/Unknwon/com"
 	"github.com/go-xorm/xorm"
+	"go.chromium.org/luci/common/sync/mutexpool"
 	"xorm.io/builder"
 )
 
@@ -70,6 +71,7 @@ type Issue struct {
 var (
 	issueTasksPat     *regexp.Regexp
 	issueTasksDonePat *regexp.Regexp
+	issueIDLock       mutexpool.P
 )
 
 const issueTasksRegexpStr = `(^\s*[-*]\s\[[\sx]\]\s.)|(\n\s*[-*]\s\[[\sx]\]\s.)`
@@ -1052,14 +1054,22 @@ func getMaxIndexOfIssue(e Engine, repoID int64) (int64, error) {
 	return maxIndex, nil
 }
 
-func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
-	opts.Issue.Title = strings.TrimSpace(opts.Issue.Title)
-
-	maxIndex, err := getMaxIndexOfIssue(e, opts.Issue.RepoID)
+func issueSyncCreate(e *xorm.Session, issue *Issue) error {
+	maxIndex, err := getMaxIndexOfIssue(e, issue.RepoID)
 	if err != nil {
 		return err
 	}
-	opts.Issue.Index = maxIndex + 1
+	issue.Index = maxIndex + 1
+
+	if _, err = e.Insert(issue); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
+	opts.Issue.Title = strings.TrimSpace(opts.Issue.Title)
 
 	if opts.Issue.MilestoneID > 0 {
 		milestone, err := getMilestoneByRepoID(e, opts.Issue.RepoID, opts.Issue.MilestoneID)
@@ -1108,8 +1118,10 @@ func newIssue(e *xorm.Session, doer *User, opts NewIssueOptions) (err error) {
 		}
 	}
 
-	// Milestone and assignee validation should happen before insert actual object.
-	if _, err = e.Insert(opts.Issue); err != nil {
+	// Calculate Issue.Index and create; make sure nobody else is doing the same for this RepoID
+	if issueIDLock.WithMutex(opts.Issue.RepoID, func() {
+		err = issueSyncCreate(e, opts.Issue)
+	}); err != nil {
 		return err
 	}