The LLM's response is generator and cannot be pickle

[BCeZn]

Bug Description

This issue arises when streaming=True is selected, causing the LLM's return value to be a generator, which cannot be pickle. The return value of the get_chat_result function in model/model.py is a generator, as shown in the following image. However, in the build_vertex function in graph/base.py, it calls await set_cache(key=vertex.id, data=vertex_dict), which includes a generator. Consequently, an error occurs during the subsequent pickle process.

Reproduction

1. Use langflow version 1.0.15 and start langflow with make init. Configure .env to use Redis (other options like memory, disk, async also have similar errors).
2. Use the Basic Prompting (Hello, World) template.
3. Enable the Stream option with the configuration as shown in the following image.

5. After running, an error occurs while building the OpenAI model. 6.

Expected behavior

It should normally print streaming output instead of being unable to build the component with streaming=true when configuring RedisCache or reporting an error of no cache found in the conversation when configured to memory. I hope you can provide an example of the correct usage of streaming=true.

Who can help?

@italojohnny @ogabrielluiz @nicoloboschi @zzzming @jordanrfrazier @mfortman11 @NadirJ

Operating System

Alibaba Cloud Linux 3 (Soaring Falcon)

Langflow Version

1.0.15

Python Version

3.12

Screenshot

No response

Flow File

No response

[dosubot[bot]]

Hey there, @BCeZn! I'm here to assist you with any bugs, questions, or contributions. Let's work together to solve the issue you're facing.

To resolve the issue of the "cannot pickle 'generator' object" error when using streaming=True with RedisCache in Langflow version 1.0.15, you need to ensure that the values being cached are serializable. Generators are not serializable with pickle, so you need to convert the generator to a list or another serializable type before caching it.

Here's how you can modify the set method to handle generators:

def set(self, key, value):
    """
    Add an item to the cache.

    Args:
        key: The key of the item.
        value: The value to cache.
    """
    try:
        # Convert generator to list if value is a generator
        if hasattr(value, '__iter__') and not isinstance(value, (str, bytes, bytearray)):
            value = list(value)
        if pickled := pickle.dumps(value):
            result = self._client.setex(key, self.expiration_time, pickled)
            if not result:
                raise ValueError("RedisCache could not set the value.")
    except TypeError as exc:
        raise TypeError("RedisCache only accepts values that can be pickled.") from exc

This modification ensures that if the value is a generator, it is converted to a list before being pickled and stored in the cache. This will prevent the "cannot pickle 'generator' object" error ^[1][2].

Additionally, the get_chat_result function in model/model.py returns a generator when the stream parameter is set to True:

if stream:
    return runnable.stream(inputs)

To handle this in the build_vertex function in graph/base.py, ensure that any data passed to set_cache is serializable. You can use a utility function like recursive_serialize_or_str to convert generators to a serializable type before caching:

def recursive_serialize_or_str(obj):
    try:
        if isinstance(obj, dict):
            return {k: recursive_serialize_or_str(v) for k, v in obj.items()}
        elif isinstance(obj, list):
            return [recursive_serialize_or_str(v) for v in obj]
        elif isinstance(obj, (AsyncIterator, Generator, Iterator)):
            return "Unconsumed Stream"
        return str(obj)
    except Exception:
        return str(obj)

By using this utility function, you can ensure that the data being cached is serializable, thus avoiding the pickling error ^[3].

Implement these changes to handle the serialization of generators properly and avoid the "cannot pickle 'generator' object" error.

To continue talking to Dosu, mention @dosu.

[StephenRi]

I have the same question, please fix it ASAP

[jordanrfrazier]

Confirmed that this still exists in 1.0.18 - generators cannot be pickled. Will look into this coming week.

[xchency]

Has this issue been resolved? Our team has also encountered this problem. It did not exist in version 1.0.14, but it has been present since version 1.0.15.

[jordanrfrazier]

It's a relatively tricky problem to pickle generators. We're discussing the best solution (and open to ideas!). For now, you may use the in-memory or async caches rather than Redis to avoid this issue, if possible for your use case. I will keep this thread updated as we discuss a solution.

LANGFLOW_LANGCHAIN_CACHE=SQLiteCache # this is the default value
LANGFLOW_CACHE_TYPE=memory # or async
LANGFLOW_CACHE_TYPE=async

[deekshanee]

@jordanrfrazier I have debugged this issue in depth , and realized the generator functions are the main culprit and if you try to serialize it to store to redis than the purpose of generators will be defeated . As Inorder to seralize it you have to resolve its value than its not the good solution even will not work and causes memory issues. But this issue needs special attention as if we keep relying on inmemory than it will not be scalable.

[deekshanee]

@jordanrfrazier @lucaseduoli do you think it can be fixed at anytime soon?

[jordanrfrazier]

@deekshanee Thanks for looking into this. The team is in the process of designing our story around scalability and stability in our v2 API. I'll make sure that this is included in those discussions, but I don't have a timeline I can share right now. As you said, it's a tricky problem, as fully serializing the generator defeats the purpose in many cases. Certain stateful generators may have a solution, but without further investigation I don't want to go with the "easy" fix of resolving the generator and unintentionally creating harder-to-diagnose memory issues.

[deekshanee]

@jordanrfrazier Sounds reasonable to me , Definately it will take time , thanks for the perspective

[dosubot[bot]]

Hi, @BCeZn. I'm Dosu, and I'm helping the langflow team manage their backlog. I'm marking this issue as stale.

Issue Summary:

• Bug in langflow v1.0.15 with streaming=True causing unpicklable generator errors with RedisCache.
• Suggested workaround: Convert generator to a list before caching.
• Problem persists in v1.0.18; discussions for a solution are ongoing.
• Temporary workaround: Use in-memory or async caches.
• Consideration for a scalable solution in the v2 API development.

Next Steps:

• Please confirm if this issue is still relevant to the latest version of langflow.
• If no update is provided, the issue will be automatically closed in 7 days.

Thank you for your understanding and contribution!