Extract runtime directory creation logic into a method

The logic to create the runtime directory currently lies in
setDefaults that is called to set up the default values of the config.
We'll need more control over this soon as we want to prune the old
runtime directories on start up. It also allows us to move the
directory creation outside of the config loading, given it's better
if one can load a config without creating directories as a side effect.

1 files changed, 54 insertions, 38 deletions

diff --git a/internal/gitaly/config/config.go b/internal/gitaly/config/config.go
index 29718876f..c269eabd1 100644
--- a/internal/gitaly/config/config.go
+++ b/internal/gitaly/config/config.go
@@ -232,45 +232,11 @@ func (cfg *Cfg) setDefaults() error {
 		cfg.Hooks.CustomHooksDir = filepath.Join(cfg.GitlabShell.Dir, "hooks")
 	}
 
-	if cfg.RuntimeDir == "" {
-		// If there is no runtime directory configured we just use a temporary runtime
-		// directory. This may not always be an ideal choice given that it's typically
-		// created at `/tmp`, which may get periodically pruned if `noatime` is set.
-		runtimeDir, err := os.MkdirTemp("", "gitaly-")
-		if err != nil {
-			return fmt.Errorf("creating temporary runtime directory: %w", err)
-		}
-
-		cfg.RuntimeDir = runtimeDir
-	} else {
-		// Otherwise, we use the configured runtime directory. Note that we don't use the
-		// runtime directory directly, but instead create a subdirectory within it which is
-		// based on the process's PID. While we could use `MkdirTemp()` instead and don't
-		// bother with preexisting directories, the benefit of using the PID here is that we
-		// can determine whether the directory may still be in use by checking whether the
-		// PID exists. Furthermore, it allows easier debugging in case one wants to inspect
-		// the runtime directory of a running Gitaly node.
-
-		runtimeDir := filepath.Join(cfg.RuntimeDir, fmt.Sprintf("gitaly-%d", os.Getpid()))
-
-		if _, err := os.Stat(runtimeDir); err != nil && !os.IsNotExist(err) {
-			return fmt.Errorf("statting runtime directory: %w", err)
-		} else if err != nil {
-			// If the directory exists already then it must be from an old invocation of
-			// Gitaly. Because we use the PID as path component we know that the old
-			// instance cannot exist anymore though, so it's safe to remove this
-			// directory now.
-			if err := os.RemoveAll(runtimeDir); err != nil {
-				return fmt.Errorf("removing old runtime directory: %w", err)
-			}
-		}
-
-		if err := os.Mkdir(runtimeDir, 0o700); err != nil {
-			return fmt.Errorf("creating runtime directory: %w", err)
-		}
-
-		cfg.RuntimeDir = runtimeDir
+	runtimeDir, err := SetupRuntimeDirectory(*cfg, os.Getpid())
+	if err != nil {
+		return err
 	}
+	cfg.RuntimeDir = runtimeDir
 
 	// The socket path must be short-ish because listen(2) fails on long
 	// socket paths. We hope/expect that os.MkdirTemp creates a directory
@@ -604,3 +570,53 @@ func (cfg *Cfg) configurePackObjectsCache() error {
 
 	return nil
 }
+
+// SetupRuntimeDirectory creates a new runtime directory. Runtime directory contains internal
+// runtime data generated by Gitaly such as the internal sockets. If cfg.RuntimeDir is set,
+// it's used as the parent directory for the runtime directory. Runtime directory owner process
+// can be identified by the suffix process ID suffixed in the directory name. If a directory already
+// exists for this process' ID, it's removed and recreated. If cfg.RuntimeDir is not set, a temporary
+// directory is used instead. SetupRuntimeDirectory returns the absolute path to the created runtime
+// directory.
+func SetupRuntimeDirectory(cfg Cfg, processID int) (string, error) {
+	var runtimeDir string
+	if cfg.RuntimeDir == "" {
+		// If there is no parent directory provided, we just use a temporary directory
+		// as the runtime directory. This may not always be an ideal choice given that
+		// it's typically created at `/tmp`, which may get periodically pruned if `noatime`
+		// is set.
+		var err error
+		runtimeDir, err = os.MkdirTemp("", "gitaly-")
+		if err != nil {
+			return "", fmt.Errorf("creating temporary runtime directory: %w", err)
+		}
+	} else {
+		// Otherwise, we use the configured runtime directory. Note that we don't use the
+		// runtime directory directly, but instead create a subdirectory within it which is
+		// based on the process's PID. While we could use `MkdirTemp()` instead and don't
+		// bother with preexisting directories, the benefit of using the PID here is that we
+		// can determine whether the directory may still be in use by checking whether the
+		// PID exists. Furthermore, it allows easier debugging in case one wants to inspect
+		// the runtime directory of a running Gitaly node.
+
+		runtimeDir = filepath.Join(cfg.RuntimeDir, fmt.Sprintf("gitaly-%d", processID))
+
+		if _, err := os.Stat(runtimeDir); err != nil && !os.IsNotExist(err) {
+			return "", fmt.Errorf("statting runtime directory: %w", err)
+		} else if err != nil {
+			// If the directory exists already then it must be from an old invocation of
+			// Gitaly. Because we use the PID as path component we know that the old
+			// instance cannot exist anymore though, so it's safe to remove this
+			// directory now.
+			if err := os.RemoveAll(runtimeDir); err != nil {
+				return "", fmt.Errorf("removing old runtime directory: %w", err)
+			}
+		}
+
+		if err := os.Mkdir(runtimeDir, 0o700); err != nil {
+			return "", fmt.Errorf("creating runtime directory: %w", err)
+		}
+	}
+
+	return runtimeDir, nil
+}