Handling update of state parameters in multiple nodes at the same time

[Eknathabhiram]

def seed_question_router(state: State):
if state['seed_question']:
return ['reasoning_question_gen','conditional_question_gen']
else:
return "get_random_node"

I have created a routing function like above. A different state parameter will be updated at both nodes. But I am receiving this error,
Traceback (most recent call last):
File "/home/x/anaconda3/envs/rag-env/lib/python3.9/runpy.py", line 197, in _run_module_as_main
return _run_code(code, main_globals, None,
File "/home/x/anaconda3/envs/rag-env/lib/python3.9/runpy.py", line 87, in _run_code
exec(code, run_globals)
File "/home/x/Documents/RAG Pipeline/evalution/workflow_nodes.py", line 148, in
for event in events:
File "/home/x/anaconda3/envs/rag-env/lib/python3.9/site-packages/langgraph/pregel/init.py", line 1218, in stream
while loop.tick(
File "/home/x/anaconda3/envs/rag-env/lib/python3.9/site-packages/langgraph/pregel/loop.py", line 285, in tick
mv_writes = apply_writes(
File "/home/x/anaconda3/envs/rag-env/lib/python3.9/site-packages/langgraph/pregel/algo.py", line 223, in apply_writes
if channels[chan].update(vals) and get_next_version is not None:
File "/home/x/anaconda3/envs/rag-env/lib/python3.9/site-packages/langgraph/channels/last_value.py", line 38, in update
raise InvalidUpdateError(
langgraph.errors.InvalidUpdateError: At key 'node': Can receive only one value per step. Use an Annotated key to handle multiple values.

[nfcampos]

Hi you need to attach a reducer to the state keys that you want to update from multiple nodes at the same time https://langchain-ai.github.io/langgraph/concepts/low_level/#reducers

[Eknathabhiram]

My question was to update different keys from multiple nodes at same time... Any way I got a solution

[RetroFiveCinque]

which is ?

[Eknathabhiram]

@RetroFiveCinque I was returning the whole state at node node...
If you are updating different key at same steps using multiple nodes you can directly return that key value as dict.

If you are trying to update the same key....You should use some reducer function.

[RetroFiveCinque]

Thanks Le mar. 5 nov. 2024 à 10:49, Abhi Pemmaraju ***@***.***> a écrit :

…

@RetroFiveCinque <https://github.com/RetroFiveCinque> I was returning the whole state at node node... If you are updating different key at same steps using multiple nodes you can directly return that key value as dict. If you are trying to update the same key....You should use some reducer function. — Reply to this email directly, view it on GitHub <#1787 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BLJ6LLHSJPD2NGROBE4C53TZ7CIDVAVCNFSM6AAAAABOTL2RDOVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTCMJVGI3TENA> . You are receiving this because you were mentioned.Message ID: ***@***.*** com>