Langflow (tracing) | Respan Docs

Langflow is a visual framework by DataStax for building multi-agent and RAG applications. It provides a drag-and-drop interface for composing LLM pipelines with components for models, prompts, tools, and data sources. Langflow is built on LangChain, so Respan tracing uses respan-instrumentation-langchain to capture component runs, underlying LangChain calls, tools, retrievers, and LLM generations — and gateway routing through the OpenAI-compatible Respan endpoint.

Set up Respan

Create an account at platform.respan.ai and grab an API key.

Run npx @respan/cli setup to set up with your coding agent.

Use Respan Gateway

See Langflow gateway setup to route this integration through the Respan gateway.

Example projects

Example projects

Setup

Install packages

$ pip install respan-ai respan-instrumentation-langchain langflow langchain langchain-openai python-dotenv

Set environment variables

$ export RESPAN_API_KEY="YOUR_RESPAN_API_KEY"
$ export RESPAN_BASE_URL="https://api.respan.ai/api"

RESPAN_API_KEY is used to export traces to Respan. Set OPENAI_API_KEY too when your Langflow components call provider-backed models.

Initialize and run

Pass LangChainInstrumentor() to Respan(instrumentations=[...]). Langflow is built on LangChain, so in Python component runs are traced automatically. Reuse one callback handler when you want independent component runs grouped into a single trace.

There are two ways to run Langflow with tracing: run custom-component code directly (as below), or run a flow you built in the Langflow UI. A UI flow must be exported first (Share → Export) to a flow.json before run_flow_from_json can load it — this quickstart ships no standalone flow file, so the runnable example uses component code directly.

1 from langchain_core.runnables import RunnableLambda
2 from respan import Respan
3 from respan_instrumentation_langchain import (
4     LangChainInstrumentor,
5     add_respan_callback,
6     get_callback_handler,
7 )
8 
9 # Activates global instrumentation. Component runs are captured automatically;
10 # the shared handler groups independent component root runs into one trace.
11 respan = Respan(instrumentations=[LangChainInstrumentor()])
12 
13 handler = get_callback_handler()
14 
15 def langflow_config(name: str):
16     return add_respan_callback(
17         {
18             "run_name": name,
19             "tags": ["respan-langchain-example", "langflow", name],
20             "metadata": {
21                 "example": name,
22                 "framework": "langflow",
23                 "langflow_component": "RoutingComponent",
24             },
25         },
26         handler,
27     )
28 
29 route_department = RunnableLambda(
30     lambda input: f"{input['department']}-workspace"
31 )
32 get_weather = RunnableLambda(
33     lambda input: f"It is sunny in {input['city']}."
34 )
35 
36 route = route_department.invoke(
37     {"department": "security"},
38     config=langflow_config("langflow_route_department"),
39 )
40 weather = get_weather.invoke(
41     {"city": "Dublin"},
42     config=langflow_config("langflow_get_weather"),
43 )
44 print(f"{route}: {weather}")

View your trace

Open the Traces page to see your Langflow workflow with component-level operations, LLM calls, retriever spans, and tool calls.

Configuration

Parameter	Type	Default	Description
`api_key`	`str \| None`	`None`	Falls back to `RESPAN_API_KEY` env var.
`base_url`	`str \| None`	`None`	Falls back to `RESPAN_BASE_URL` env var.
`instrumentations`	`list`	`[]`	Plugin instrumentations to activate, e.g. `LangChainInstrumentor()`.
`group_langflow_root_runs`	`bool`	`True` via `get_callback_handler()`	Groups independent Langflow component root runs into one trace.
`include_content`	`bool`	`True`	Includes component inputs and outputs on spans.
`include_metadata`	`bool`	`True`	Includes Langflow tags, metadata, and serialized runnable details.
`customer_identifier`	`str \| None`	`None`	Default customer identifier for all spans.
`metadata`	`dict \| None`	`None`	Default metadata attached to all spans.
`environment`	`str \| None`	`None`	Environment tag, e.g. `"production"`.

Attributes

In Respan()

Set defaults at initialization — these apply to all spans.

1 from respan import Respan
2 from respan_instrumentation_langchain import LangChainInstrumentor
3 
4 respan = Respan(
5     instrumentations=[LangChainInstrumentor()],
6     customer_identifier="user_123",
7     metadata={"service": "langflow-api", "version": "1.0.0"},
8 )

With propagate_attributes

Override per-request using a context scope.

1 from langflow.load import run_flow_from_json
2 from respan import propagate_attributes
3 
4 def handle_request(user_id: str, question: str):
5     with propagate_attributes(
6         customer_identifier=user_id,
7         thread_identifier="conv_abc_123",
8         metadata={"plan": "pro"},
9     ):
10         result = run_flow_from_json(flow="flow.json", input_value=question)
11         print(result)

Attribute	Type	Description
`customer_identifier`	`str`	Identifies the end user in Respan analytics.
`thread_identifier`	`str`	Groups related messages into a conversation.
`metadata`	`dict`	Custom key-value pairs. Merged with default metadata.

Decorators (optional)

Decorators are not required. Langflow runs are traced through LangChain callbacks. Use @workflow and @task (Python) or withWorkflow and withTask (TypeScript) when you want to group one or more flow executions inside a named application workflow.

1 from respan import workflow, task
2 
3 @task(name="run_langflow_flow")
4 def run_langflow_flow(question: str):
5     return run_flow_from_json(flow="flow.json", input_value=question)
6 
7 @workflow(name="langflow_request")
8 def pipeline(question: str):
9     print(run_langflow_flow(question))
10 
11 pipeline("What is the meaning of life?")

Examples

Custom component callback grouping

Use one callback handler for the component invocation so multiple LangChain calls in the same custom component share a trace.

1 from respan_instrumentation_langchain import add_respan_callback, get_callback_handler
2 
3 handler = get_callback_handler()
4 config = add_respan_callback(
5     {
6         "run_name": "langflow_component",
7         "tags": ["langflow", "custom-component"],
8         "metadata": {
9             "framework": "langflow",
10             "langflow_component": "RoutingComponent",
11         },
12     },
13     handler,
14 )
15 
16 result = chain.invoke({"question": "Route this request"}, config=config)

Exported flows

Export the flow from the Langflow UI (Share → Export) to a flow.json first. Exported flows can then be run normally after Respan telemetry is initialized. For custom components inside the flow, pass add_respan_callback(...) when invoking LangChain runnables.

1 from langflow.load import run_flow_from_json
2 
3 result = run_flow_from_json(
4     flow="path/to/your/flow.json",
5     input_value="Summarize this support request.",
6 )
7 print(result)