From 5675ea31c8e92a6cc8e29daf96c33278ddc7c6f2 Mon Sep 17 00:00:00 2001
From: arkn98 <2424696-arkn98@users.noreply.gitlab.com>
Date: Sun, 20 Aug 2023 01:00:58 -0400
Subject: [PATCH] streamcache: add support for symlinks

Streamcache.filestore, currently, doesn't work when its directory is a
symlink; the cleanup function ends up deleting it (see [1]). This
commit fixes it by resolving the symlink to its absolute path during
configuration.

The side-effects of this change are:

- The log messages, label values, etc. will use the resolved path
  instead of the value set in pack_objects_cache.dir, if it was a
  symlink.

- Since we lstat the path to check if it is a symlink, the errors that
  might happen during the cleanup (when `cleanWalk()` is run) can now
  happen during configuration.

1. https://gitlab.com/gitlab-org/gitaly/-/issues/4845

Fixes: https://gitlab.com/gitlab-org/gitaly/-/issues/4845
Changelog: added
Signed-off-by: arkn98 <2424696-arkn98@users.noreply.gitlab.com>
---
 internal/gitaly/config/config.go | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/internal/gitaly/config/config.go b/internal/gitaly/config/config.go
index 5b02d15bfe9..1bdb7e25ee4 100644
--- a/internal/gitaly/config/config.go
+++ b/internal/gitaly/config/config.go
@@ -934,9 +934,40 @@ func (cfg *Cfg) configurePackObjectsCache() error {
 		return errPackObjectsCacheRelativePath
 	}
 
+	realPath, err := evalSymlink(poc.Dir)
+	if err != nil {
+		return fmt.Errorf("pack_objects_cache.dir symlink cannot be resolved: %w", err)
+	}
+	poc.Dir = realPath
+
 	return nil
 }
 
+func evalSymlink(path string) (string, error) {
+	// check if path is a symlink
+	fileInfo, err := os.Lstat(path)
+	if err != nil {
+		return "", err
+	}
+
+	if fileInfo.Mode()&os.ModeSymlink == 0 {
+		// path is not a symlink
+		return path, nil
+	}
+
+	realPath, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		return "", err
+	}
+
+	// the evaluated path can be relative
+	if !filepath.IsAbs(realPath) {
+		return filepath.Abs(realPath)
+	}
+
+	return realPath, 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
-- 
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