fix: repository cloning race condition (#2341) (#2348)

* fix: repository cloning race condition (#2341) * fix: switched from sync to golang.org/x/sync/semaphore * fix: check value of sem.Acquire(...)
runatlantis · Jul 27, 2022 · e0e29bd · e0e29bd
1 parent fe67a2a
commit e0e29bd
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diff --git a/go.mod b/go.mod
@@ -43,6 +43,7 @@ require (
 	go.etcd.io/bbolt v1.3.6
 	go.uber.org/zap v1.21.0
 	golang.org/x/oauth2 v0.0.0-20220411215720-9780585627b5
+	golang.org/x/sync v0.0.0-20220513210516-0976fa681c29
 	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211
 	gopkg.in/go-playground/validator.v9 v9.31.0
 	gopkg.in/yaml.v2 v2.4.0

diff --git a/go.sum b/go.sum
@@ -717,6 +717,7 @@ golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20220513210516-0976fa681c29 h1:w8s32wxx3sY+OjLlv9qltkLU5yvJzxjjgiHWLjdIcw4=
 golang.org/x/sync v0.0.0-20220513210516-0976fa681c29/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

diff --git a/server/events/working_dir.go b/server/events/working_dir.go
@@ -14,20 +14,25 @@
 package events
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/pkg/errors"
 	"github.com/runatlantis/atlantis/server/events/models"
 	"github.com/runatlantis/atlantis/server/logging"
+	"golang.org/x/sync/semaphore"
 )
 
 const workingDirPrefix = "repos"
 
+var cloneLocks sync.Map
+
 //go:generate pegomock generate -m --use-experimental-model-gen --package mocks -o mocks/mock_working_dir.go WorkingDir
 //go:generate pegomock generate -m --use-experimental-model-gen --package events WorkingDir
 
@@ -199,6 +204,18 @@ func (w *FileWorkspace) forceClone(log logging.SimpleLogging,
 	headRepo models.Repo,
 	p models.PullRequest) error {
 
+	value, _ := cloneLocks.LoadOrStore(cloneDir, semaphore.NewWeighted(1))
+	sem := value.(*semaphore.Weighted)
+
+	defer sem.Release(1)
+	if acquired := sem.TryAcquire(1); !acquired {
+		err := sem.Acquire(context.TODO(), 1)
+		if err != nil {
+			return errors.Wrap(err, "waiting for repository to be cloned")
+		}
+		return nil
+	}
+
 	err := os.RemoveAll(cloneDir)
 	if err != nil {
 		return errors.Wrapf(err, "deleting dir %q before cloning", cloneDir)