From 9f546ee0f35afe0e7d7d64d15a92d715bd3301b2 Mon Sep 17 00:00:00 2001
From: Moshe Immerman <moshe@flanksource.com>
Date: Sun, 26 Nov 2023 20:19:29 +0200
Subject: [PATCH] fix: lock git checkout dirs

---
 checks/exec.go     | 16 +++++++++++++---
 pkg/utils/utils.go | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/checks/exec.go b/checks/exec.go
index d6139ecd6..d6ef7bee1 100644
--- a/checks/exec.go
+++ b/checks/exec.go
@@ -9,17 +9,21 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"time"
 
 	"github.com/flanksource/canary-checker/api/context"
 	"github.com/flanksource/canary-checker/api/external"
 	v1 "github.com/flanksource/canary-checker/api/v1"
 	"github.com/flanksource/canary-checker/pkg"
+	"github.com/flanksource/canary-checker/pkg/utils"
 	"github.com/flanksource/commons/files"
 	"github.com/flanksource/commons/hash"
 	"github.com/flanksource/duty/models"
 	"github.com/hashicorp/go-getter"
 )
 
+var checkoutLocks = utils.NamedLock{}
+
 type ExecChecker struct {
 }
 
@@ -91,11 +95,17 @@ func (c *ExecChecker) prepareEnvironment(ctx *context.Context, check v1.ExecChec
 
 		result.mountPoint = check.Checkout.Destination
 		if result.mountPoint == "" {
-			pwd, _ := os.Getwd()
-			result.mountPoint = filepath.Join(pwd, ".downloads", hash.Sha256Hex(goGetterURL))
+			result.mountPoint = filepath.Join("exec-checkout", hash.Sha256Hex(goGetterURL))
+		}
+		// We allow multiple checks to use the same checkout location, for disk space and performance reasons
+		// however git does not allow multiple operations to be performed, so we need to lock it
+		lock := checkoutLocks.TryLock(result.mountPoint, 5*time.Minute)
+		if lock == nil {
+			return nil, fmt.Errorf("failed to acquire checkout lock for %s", result.mountPoint)
 		}
+		defer lock.Release()
 
-		if err := checkout(ctx, goGetterURL, result.mountPoint); err != nil {
+		if err := checkout(ctx, goGetterURL, filepath.Join(os.TempDir(), result.mountPoint)); err != nil {
 			return nil, fmt.Errorf("error checking out: %w", err)
 		}
 	}
diff --git a/pkg/utils/utils.go b/pkg/utils/utils.go
index b60bea400..d73622ba4 100644
--- a/pkg/utils/utils.go
+++ b/pkg/utils/utils.go
@@ -1,16 +1,48 @@
 package utils
 
 import (
+	"context"
 	"crypto/md5"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"sync"
 	"time"
 
+	"golang.org/x/sync/semaphore"
+
 	"github.com/google/uuid"
 	"k8s.io/apimachinery/pkg/util/duration"
 )
 
+type NamedLock struct {
+	locks sync.Map
+}
+
+type Unlocker interface {
+	Release()
+}
+
+type unlocker struct {
+	lock *semaphore.Weighted
+}
+
+func (u *unlocker) Release() {
+	u.lock.Release(1)
+}
+
+func (n *NamedLock) TryLock(name string, timeout time.Duration) Unlocker {
+	o, _ := n.locks.LoadOrStore(name, semaphore.NewWeighted(1))
+	lock := o.(*semaphore.Weighted)
+
+	ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(timeout))
+	defer cancel()
+	if err := lock.Acquire(ctx, 1); err != nil {
+		return nil
+	}
+	return &unlocker{lock}
+}
+
 func Age(d time.Duration) string {
 	if d.Milliseconds() == 0 {
 		return "0ms"