How to enable logging tracer output in Haystack

Tracing in Haystack records pipeline and component activity while a pipeline run is being debugged. The built-in LoggingTracer sends those trace records through Python logging, which gives a local script visibility into component names, payload shapes, and pipeline output without a separate tracing backend.

Python code enables LoggingTracer with tracing.enable_tracing(). Content tracing is a separate switch because inputs and outputs can contain prompts, documents, API responses, user text, or other sensitive payloads.

A logger scoped to haystack.tracing.logging_tracer keeps the console focused on trace records instead of unrelated framework debug lines. A small custom component makes the logged component span, content tags, and final pipeline output easy to recognize before the same setup is added to a larger pipeline.

1. Create haystack_logging_tracer_demo.py with the Haystack imports and a logger limited to LoggingTracer debug records.

   haystack_logging_tracer_demo.py

   import logging
    
   from haystack import Pipeline, component, tracing
   from haystack.tracing.logging_tracer import LoggingTracer
    
    
   logging.basicConfig(
       format="%(levelname)s:%(name)s:%(message)s",
       level=logging.WARNING,
   )
   logging.getLogger("haystack.tracing.logging_tracer").setLevel(logging.DEBUG)

   The LoggingTracer class is built into haystack-ai and does not need an additional tracing package.
   Related: How to install Haystack with pip

2. Enable Haystack tracing below the logger setup with a LoggingTracer instance.

   tracing.tracer.is_content_tracing_enabled = True
   tracing.enable_tracing(LoggingTracer(tags_color_strings={}))

   Content tracing writes component payloads to logs, including any prompts, documents, chat messages, API responses, or credentials passed through a pipeline. Only payloads that are safe to store belong in content tracing.

3. Append the DebugEcho component below the tracing configuration.

   @component
   class DebugEcho:
       @component.output_types(reply=str)
       def run(self, text: str):
           return {"reply": text.upper()}

4. Append the pipeline construction and execution below the component class.

    
   pipeline = Pipeline()
   pipeline.add_component("debug_echo", DebugEcho())
    
   result = pipeline.run({"debug_echo": {"text": "trace me"}})
    
   print(f"reply={result['debug_echo']['reply']}")

5. Run the completed demo to verify the component trace content and final pipeline result.

   $ python3 haystack_logging_tracer_demo.py
   reply=TRACE ME
   DEBUG:haystack.tracing.logging_tracer:Operation: haystack.component.run
   DEBUG:haystack.tracing.logging_tracer:haystack.component.name=debug_echo
   DEBUG:haystack.tracing.logging_tracer:haystack.component.type=DebugEcho
   DEBUG:haystack.tracing.logging_tracer:haystack.component.fully_qualified_type=__main__.DebugEcho
   DEBUG:haystack.tracing.logging_tracer:haystack.component.input_types={"text": "str"}
   DEBUG:haystack.tracing.logging_tracer:haystack.component.input_spec={"text": {"type": "str", "senders": []}}
   DEBUG:haystack.tracing.logging_tracer:haystack.component.output_spec={"reply": {"type": "str", "receivers": []}}
   DEBUG:haystack.tracing.logging_tracer:haystack.component.input={"text": "trace me"}
   DEBUG:haystack.tracing.logging_tracer:haystack.component.visits=1
   DEBUG:haystack.tracing.logging_tracer:haystack.component.output={"reply": "TRACE ME"}
   DEBUG:haystack.tracing.logging_tracer:Operation: haystack.pipeline.run
   DEBUG:haystack.tracing.logging_tracer:haystack.pipeline.input_data={"debug_echo": {"text": "trace me"}}
   DEBUG:haystack.tracing.logging_tracer:haystack.pipeline.output_data={"debug_echo": {"reply": "TRACE ME"}}
   DEBUG:haystack.tracing.logging_tracer:haystack.pipeline.metadata={}
   DEBUG:haystack.tracing.logging_tracer:haystack.pipeline.max_runs_per_component=100

   Python logging writes to stderr while print() writes to stdout, so terminals and runners can show the final reply=TRACE ME line before or after the pipeline-level tracer lines.