fix: Use str() to calculate fingerprint instead of json.dumps

This is to avoid serialization issue for some fields that are not json serializable. meanwhile restructure the debug logs in context cache manager for better debugging potential issues. PiperOrigin-RevId: 811182492

Author: seanzhougoogle

src/google/adk/models/gemini_context_cache_manager.py

@@ -68,8 +68,19 @@ async def handle_context_caching(
  """
  # Check if we have existing cache metadata and if it's valid
  if llm_request.cache_metadata:
+ logger.debug(
+ "Found existing cache metadata: cache_name=%s, invocations_used=%d,"
+ " cached_contents_count=%d",
+ llm_request.cache_metadata.cache_name,
+ llm_request.cache_metadata.invocations_used,
+ llm_request.cache_metadata.cached_contents_count,
+ )
  if await self._is_cache_valid(llm_request):
  # Valid cache found - use it
+ logger.debug(
+ "Cache is valid, reusing cache: %s",
+ llm_request.cache_metadata.cache_name,
+ )
  cache_name = llm_request.cache_metadata.cache_name
  cache_contents_count = llm_request.cache_metadata.cached_contents_count
  self._apply_cache_to_request(
@@ -78,13 +89,22 @@ async def handle_context_caching(
  return llm_request.cache_metadata.model_copy()
  else:
  # Invalid cache - clean it up
+ logger.debug(
+ "Cache is invalid, cleaning up: %s",
+ llm_request.cache_metadata.cache_name,
+ )
  await self.cleanup_cache(llm_request.cache_metadata.cache_name)
  llm_request.cache_metadata = None
 
  # Find contents to cache for new cache creation
  cache_contents_count = self._find_count_of_contents_to_cache(
  llm_request.contents
  )
+ logger.debug(
+ "Determined to cache %d contents from %d total contents",
+ cache_contents_count,
+ len(llm_request.contents),
+ )
 
  # Create new cache with the determined contents
  cache_metadata = await self._create_new_cache_with_contents(
@@ -97,6 +117,9 @@ async def handle_context_caching(
  self._apply_cache_to_request(
  llm_request, cache_metadata.cache_name, cache_contents_count
  )
+ logger.debug(
+ "Successfully applied cache to request: %s", cache_metadata.cache_name
+ )
 
  return cache_metadata
 
@@ -218,8 +241,8 @@ def _generate_cache_fingerprint(
  contents_data.append(content.model_dump())
  fingerprint_data["cached_contents"] = contents_data
 
- # Generate hash
- fingerprint_str = json.dumps(fingerprint_data, sort_keys=True)
+ # Generate hash using str() instead of json.dumps() to handle bytes
+ fingerprint_str = str(fingerprint_data)
  return hashlib.sha256(fingerprint_str.encode()).hexdigest()[:16]
 
  async def _create_new_cache_with_contents(
@@ -310,6 +333,10 @@ async def _create_gemini_cache(
  # Add system instruction if present
  if llm_request.config and llm_request.config.system_instruction:
  cache_config.system_instruction = llm_request.config.system_instruction
+ logger.debug(
+ "Added system instruction to cache config (length=%d)",
+ len(llm_request.config.system_instruction),
+ )
 
  # Add tools if present
  if llm_request.config and llm_request.config.tools:
@@ -319,36 +346,38 @@ async def _create_gemini_cache(
  if llm_request.config and llm_request.config.tool_config:
  cache_config.tool_config = llm_request.config.tool_config
 
- try:
- cached_content = await self.genai_client.aio.caches.create(
- model=llm_request.model,
- config=cache_config,
- )
- # Set precise creation timestamp right after cache creation
- created_at = time.time()
- logger.info("Cache created successfully: %s", cached_content.name)
-
- # Return complete cache metadata with precise timing
- return CacheMetadata(
- cache_name=cached_content.name,
- expire_time=created_at + llm_request.cache_config.ttl_seconds,
- fingerprint=self._generate_cache_fingerprint(
- llm_request, cache_contents_count
- ),
- invocations_used=1,
- cached_contents_count=cache_contents_count,
- created_at=created_at,
- )
- except Exception as e:
- logger.error("Failed to create Gemini cache: %s", e)
- raise
+ logger.debug(
+ "Creating cache with model %s and config: %s",
+ llm_request.model,
+ cache_config,
+ )
+ cached_content = await self.genai_client.aio.caches.create(
+ model=llm_request.model,
+ config=cache_config,
+ )
+ # Set precise creation timestamp right after cache creation
+ created_at = time.time()
+ logger.info("Cache created successfully: %s", cached_content.name)
+
+ # Return complete cache metadata with precise timing
+ return CacheMetadata(
+ cache_name=cached_content.name,
+ expire_time=created_at + llm_request.cache_config.ttl_seconds,
+ fingerprint=self._generate_cache_fingerprint(
+ llm_request, cache_contents_count
+ ),
+ invocations_used=1,
+ cached_contents_count=cache_contents_count,
+ created_at=created_at,
+ )
 
  async def cleanup_cache(self, cache_name: str) -> None:
  """Clean up cache by deleting it.
 
  Args:
  cache_name: Name of cache to delete
  """
+ logger.debug("Attempting to delete cache: %s", cache_name)
  try:
  await self.genai_client.aio.caches.delete(name=cache_name)
  logger.info("Cache cleaned up: %s", cache_name)