Fix performance issues in /deployment/version/ endpoint

- Add proper cache expiration with 5-minute TTL
- Optimize git log file reading to avoid loading entire file
- Read only last chunk (1024 bytes) instead of all lines
- Add shorter TTL (30s) for error cases to allow retry
- Improve error handling with UnicodeDecodeError support
- Maintain backward compatibility and security (no subprocess calls)

This fixes the 30-second response time issue by implementing efficient
caching and optimized file I/O operations.

ivatar/views.py

@@ -845,9 +845,11 @@ class StatsView(TemplateView, JsonResponse):
         return JsonResponse(retval)
 
 
-# Thread-safe version cache
+# Thread-safe version cache with timestamp
 _version_cache = None
+_version_cache_timestamp = None
 _version_cache_lock = threading.Lock()
+_VERSION_CACHE_TTL = 300  # 5 minutes cache TTL
 
 
 def _get_git_info_from_files():
@@ -889,15 +891,29 @@ def _get_git_info_from_files():
             branch_name = "detached"
 
         # Try to get commit date from git log file (if available)
+        # Optimize: read only the last line instead of entire file
         commit_date = None
         log_file = path.join(git_dir, "logs", "HEAD")
         if path.exists(log_file):
             try:
-                with open(log_file, "r") as f:
-                    # Read last line to get most recent commit info
-                    lines = f.readlines()
-                    if lines:
-                        last_line = lines[-1].strip()
+                with open(log_file, "rb") as f:
+                    # Seek to end and read backwards to find last line
+                    f.seek(0, 2)  # Seek to end
+                    file_size = f.tell()
+
+                    # Read backwards in chunks to find the last line
+                    chunk_size = min(1024, file_size)
+                    f.seek(max(0, file_size - chunk_size))
+                    chunk = f.read().decode("utf-8", errors="ignore")
+
+                    # Find the last newline
+                    last_newline = chunk.rfind("\n")
+                    if last_newline != -1:
+                        last_line = chunk[last_newline + 1:].strip()
+                    else:
+                        last_line = chunk.strip()
+
+                    if last_line:
                         # Git log format: <old_hash> <new_hash> <author> <timestamp> <timezone> <message>
                         parts = last_line.split("\t")
                         if len(parts) >= 2:
@@ -910,7 +926,7 @@ def _get_git_info_from_files():
                                 commit_date = datetime.datetime.fromtimestamp(
                                     timestamp
                                 ).strftime("%Y-%m-%d %H:%M:%S %z")
-            except (ValueError, IndexError):
+            except (ValueError, IndexError, UnicodeDecodeError):
                 pass
 
         # Fallback: try to get date from commit object if available
@@ -941,21 +957,33 @@ def _get_git_info_from_files():
 
 def _get_cached_version_info():
     """
-    Get cached version information, loading it if not available
+    Get cached version information, loading it if not available or expired
     """
-    global _version_cache
+    global _version_cache, _version_cache_timestamp
+    import time
 
     with _version_cache_lock:
-        if _version_cache is None:
+        current_time = time.time()
+
+        # Check if cache is expired or doesn't exist
+        if (
+            _version_cache is None
+            or _version_cache_timestamp is None
+            or current_time - _version_cache_timestamp > _VERSION_CACHE_TTL
+        ):
+
             # Get version info from git files
             _version_cache = _get_git_info_from_files()
+            _version_cache_timestamp = current_time
 
-            # If that fails, return error
+            # If that fails, return error but don't cache it for long
             if _version_cache is None:
                 _version_cache = {
                     "error": "Unable to determine version - .git directory not found",
                     "deployment_status": "unknown",
                 }
+                # Set shorter TTL for error cases to allow retry
+                _version_cache_timestamp = current_time - _VERSION_CACHE_TTL + 30
 
         return _version_cache