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83 lines
2.8 KiB
Plaintext
83 lines
2.8 KiB
Plaintext
---
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title: "Custom Tracer"
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id: custom-tracer
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slug: "/tracing-custom-tracer"
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description: "Learn how to connect Haystack to a custom tracing backend by implementing the Tracer interface."
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---
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# Custom Tracer
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Learn how to connect Haystack to a custom tracing backend by implementing the `Tracer` interface.
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<div className="key-value-table">
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| | |
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| --- | --- |
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| **Base classes** | `Tracer` and `Span` |
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| **How to enable** | Implement the `Tracer` interface, then `tracing.enable_tracing(your_tracer)` |
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| **Content tracing** | Optional. Set `HAYSTACK_CONTENT_TRACING_ENABLED` to `true` to trace component inputs and outputs |
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| **Package** | Built into Haystack |
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| **GitHub link** | https://github.com/deepset-ai/haystack/blob/main/haystack/tracing/tracer.py |
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</div>
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## Overview
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If your tracing backend isn't supported out of the box, you can connect it to Haystack by implementing the `Tracer` interface. This gives you full control over how spans are created and how tags are recorded.
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## Usage
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1. Implement the `Tracer` interface. The following code snippet provides an example using the OpenTelemetry package:
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```python
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import contextlib
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from typing import Optional, Dict, Any, Iterator
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from opentelemetry import trace
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from opentelemetry.trace import NonRecordingSpan
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from haystack.tracing import Tracer, Span
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from haystack.tracing import utils as tracing_utils
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import opentelemetry.trace
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class OpenTelemetrySpan(Span):
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def __init__(self, span: opentelemetry.trace.Span) -> None:
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self._span = span
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def set_tag(self, key: str, value: Any) -> None:
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# Tracing backends usually don't support any tag value
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# `coerce_tag_value` forces the value to either be a Python
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# primitive (int, float, boolean, str) or tries to dump it as string.
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coerced_value = tracing_utils.coerce_tag_value(value)
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self._span.set_attribute(key, coerced_value)
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class OpenTelemetryTracer(Tracer):
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def __init__(self, tracer: opentelemetry.trace.Tracer) -> None:
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self._tracer = tracer
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@contextlib.contextmanager
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def trace(self, operation_name: str, tags: Optional[Dict[str, Any]] = None) -> Iterator[Span]:
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with self._tracer.start_as_current_span(operation_name) as span:
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span = OpenTelemetrySpan(span)
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if tags:
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span.set_tags(tags)
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yield span
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def current_span(self) -> Optional[Span]:
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current_span = trace.get_current_span()
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if isinstance(current_span, NonRecordingSpan):
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return None
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return OpenTelemetrySpan(current_span)
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```
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2. Tell Haystack to use your custom tracer:
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```python
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from haystack import tracing
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haystack_tracer = OpenTelemetryTracer(tracer)
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tracing.enable_tracing(haystack_tracer)
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```
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