cgroups: Handle nil repojc-pick-handle-nil-repo-into-15-0-stable

If a command's repo is nil, handle it gracefully by adding the command
to a cgroup by using the command arguments as a key for the circular
hash.

While we're at it, fix a test that was doing the checksum incorrectly.
This didn't make a difference in the test however, because we were using
the groupID we calculated ourselves to check for the location of the
cgroup file.

Changelog: fixed

2 files changed, 44 insertions, 13 deletions

diff --git a/internal/cgroups/v1_linux.go b/internal/cgroups/v1_linux.go
index 49802bcb8..3e37c6205 100644
--- a/internal/cgroups/v1_linux.go
+++ b/internal/cgroups/v1_linux.go
@@ -103,9 +103,17 @@ func (cg *CGroupV1Manager) AddCommand(
 	cmd *command.Command,
 	repo repository.GitRepo,
 ) error {
+	var key string
+	if repo == nil {
+		key = strings.Join(cmd.Args(), "/")
+	} else {
+		key = repo.GetStorageName() + "/" + repo.GetRelativePath()
+	}
+
 	checksum := crc32.ChecksumIEEE(
-		[]byte(repo.GetStorageName() + "/" + repo.GetRelativePath()),
+		[]byte(key),
 	)
+
 	groupID := uint(checksum) % cg.cfg.Repositories.Count
 	cgroupPath := cg.repoPath(int(groupID))
 
diff --git a/internal/cgroups/v1_linux_test.go b/internal/cgroups/v1_linux_test.go
index 347973374..03a498a11 100644
--- a/internal/cgroups/v1_linux_test.go
+++ b/internal/cgroups/v1_linux_test.go
@@ -69,7 +69,7 @@ func TestAddCommand(t *testing.T) {
 	}
 
 	config := defaultCgroupsConfig()
-	config.Repositories.Count = 1
+	config.Repositories.Count = 10
 	config.Repositories.MemoryBytes = 1024
 	config.Repositories.CPUShares = 16
 
@@ -90,21 +90,44 @@ func TestAddCommand(t *testing.T) {
 		hierarchy: mock.hierarchy,
 	}
 
-	require.NoError(t, v1Manager2.AddCommand(cmd2, repo))
+	t.Run("without a repository", func(t *testing.T) {
+		require.NoError(t, v1Manager2.AddCommand(cmd2, nil))
 
-	checksum := crc32.ChecksumIEEE([]byte(strings.Join([]string{"default", "path/to/repo.git"}, "")))
-	groupID := uint(checksum) % config.Repositories.Count
+		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", os.Getpid()), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
-		content := readCgroupFile(t, path)
+		for _, s := range mock.subsystems {
+			path := filepath.Join(mock.root, string(s.Name()), "gitaly",
+				fmt.Sprintf("gitaly-%d", os.Getpid()), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
+			content := readCgroupFile(t, path)
 
-		pid, err := strconv.Atoi(string(content))
-		require.NoError(t, err)
+			pid, err := strconv.Atoi(string(content))
+			require.NoError(t, err)
 
-		require.Equal(t, cmd2.Pid(), pid)
-	}
+			require.Equal(t, cmd2.Pid(), pid)
+		}
+	})
+
+	t.Run("with a repository", func(t *testing.T) {
+		require.NoError(t, v1Manager2.AddCommand(cmd2, repo))
+
+		checksum := crc32.ChecksumIEEE([]byte(strings.Join([]string{
+			"default",
+			"path/to/repo.git",
+		}, "/")))
+		groupID := uint(checksum) % config.Repositories.Count
+
+		for _, s := range mock.subsystems {
+			path := filepath.Join(mock.root, string(s.Name()), "gitaly",
+				fmt.Sprintf("gitaly-%d", os.Getpid()), fmt.Sprintf("repos-%d", groupID), "cgroup.procs")
+			content := readCgroupFile(t, path)
+
+			pid, err := strconv.Atoi(string(content))
+			require.NoError(t, err)
+
+			require.Equal(t, cmd2.Pid(), pid)
+		}
+	})
 }
 
 func TestCleanup(t *testing.T) {