cgroups: Add helper to calculate cgroup ID

We repeatedly calculate the cgroup ID for command in our tests.

Deduplicate these instances into a helper method.

3 files changed, 18 insertions, 16 deletions

diff --git a/internal/cgroups/testhelper_test.go b/internal/cgroups/testhelper_test.go
index 5f594195a..55d0ae338 100644
--- a/internal/cgroups/testhelper_test.go
+++ b/internal/cgroups/testhelper_test.go
@@ -3,6 +3,8 @@
 package cgroups
 
 import (
+	"hash/crc32"
+	"strings"
 	"testing"
 
 	"gitlab.com/gitlab-org/gitaly/v16/internal/testhelper"
@@ -11,3 +13,9 @@ import (
 func TestMain(m *testing.M) {
 	testhelper.Run(m)
 }
+
+// calcGroupID calculates the repository cgroup ID for the key provided.
+func calcGroupID(key []string, ct uint) uint {
+	checksum := crc32.ChecksumIEEE([]byte(strings.Join(key, "/")))
+	return uint(checksum) % ct
+}
diff --git a/internal/cgroups/v1_linux_test.go b/internal/cgroups/v1_linux_test.go
index ba8a55b29..e28df87df 100644
--- a/internal/cgroups/v1_linux_test.go
+++ b/internal/cgroups/v1_linux_test.go
@@ -4,7 +4,6 @@ package cgroups
 
 import (
 	"fmt"
-	"hash/crc32"
 	"io/fs"
 	"os"
 	"os/exec"
@@ -235,12 +234,11 @@ func TestAddCommand(t *testing.T) {
 	v1Manager2 := mock.newCgroupManager(config, testhelper.SharedLogger(t), pid)
 
 	t.Run("without overridden key", func(t *testing.T) {
+		groupID := calcGroupID(cmd2.Args, config.Repositories.Count)
+
 		_, err := v1Manager2.AddCommand(cmd2)
 		require.NoError(t, err)
 
-		checksum := crc32.ChecksumIEEE([]byte(strings.Join(cmd2.Args, "/")))
-		groupID := uint(checksum) % config.Repositories.Count
-
 		for _, s := range mock.subsystems {
 			path := filepath.Join(mock.root, string(s.Name()), "gitaly",
 				fmt.Sprintf("gitaly-%d", pid), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
@@ -254,15 +252,14 @@ func TestAddCommand(t *testing.T) {
 	})
 
 	t.Run("with overridden key", func(t *testing.T) {
+		overridenGroupID := calcGroupID([]string{"foobar"}, config.Repositories.Count)
+
 		_, err := v1Manager2.AddCommand(cmd2, WithCgroupKey("foobar"))
 		require.NoError(t, err)
 
-		checksum := crc32.ChecksumIEEE([]byte("foobar"))
-		groupID := uint(checksum) % config.Repositories.Count
-
 		for _, s := range mock.subsystems {
 			path := filepath.Join(mock.root, string(s.Name()), "gitaly",
-				fmt.Sprintf("gitaly-%d", pid), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
+				fmt.Sprintf("gitaly-%d", pid), fmt.Sprintf("repos-%d", overridenGroupID), "cgroup.procs")
 			content := readCgroupFile(t, path)
 
 			cmdPid, err := strconv.Atoi(string(content))
diff --git a/internal/cgroups/v2_linux_test.go b/internal/cgroups/v2_linux_test.go
index 96c5a3fdb..347ce2498 100644
--- a/internal/cgroups/v2_linux_test.go
+++ b/internal/cgroups/v2_linux_test.go
@@ -4,7 +4,6 @@ package cgroups
 
 import (
 	"fmt"
-	"hash/crc32"
 	"io/fs"
 	"os"
 	"os/exec"
@@ -223,12 +222,11 @@ func TestAddCommandV2(t *testing.T) {
 	v2Manager2 := mock.newCgroupManager(config, testhelper.SharedLogger(t), pid)
 
 	t.Run("without overridden key", func(t *testing.T) {
+		groupID := calcGroupID(cmd2.Args, config.Repositories.Count)
+
 		_, err := v2Manager2.AddCommand(cmd2)
 		require.NoError(t, err)
 
-		checksum := crc32.ChecksumIEEE([]byte(strings.Join(cmd2.Args, "/")))
-		groupID := uint(checksum) % config.Repositories.Count
-
 		path := filepath.Join(mock.root, "gitaly",
 			fmt.Sprintf("gitaly-%d", pid), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
 		content := readCgroupFile(t, path)
@@ -240,14 +238,13 @@ func TestAddCommandV2(t *testing.T) {
 	})
 
 	t.Run("with overridden key", func(t *testing.T) {
+		overriddenGroupID := calcGroupID([]string{"foobar"}, config.Repositories.Count)
+
 		_, err := v2Manager2.AddCommand(cmd2, WithCgroupKey("foobar"))
 		require.NoError(t, err)
 
-		checksum := crc32.ChecksumIEEE([]byte("foobar"))
-		groupID := uint(checksum) % config.Repositories.Count
-
 		path := filepath.Join(mock.root, "gitaly",
-			fmt.Sprintf("gitaly-%d", pid), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
+			fmt.Sprintf("gitaly-%d", pid), fmt.Sprintf("repos-%d", overriddenGroupID), "cgroup.procs")
 		content := readCgroupFile(t, path)
 
 		cmdPid, err := strconv.Atoi(string(content))