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Custom Spans

While the spans created via Phoenix and OpenInference creates a solid foundation for tracing your application, sometimes you may need to create customized LLM spans.
Phoenix and OpenInference use OpenTelemetry Trace API to create spans. Because Phoenix supports OpenTelemetry, this means that you can perform manual instrumentation, no LLM framework required! This guide will help you understand how to create and customize spans using OpenTelemetry Trace API.
First, ensure you have the API and SDK packages:
pip install opentelemetry-api
pip install opentelemetry-sdk
Let's next install the OpenInference Semantic Conventions package so that we can construct spans with LLM semantic conventions:
pip install openinference-semantic-conventions
For full documentation on the OpenInference semantic conventions, please consult the specification

Acquire Tracer

To start tracing, you'll need get a tracer (note that this assumes you already have a trace provider configured):
from opentelemetry import trace
# Creates a tracer from the global tracer provider
tracer = trace.get_tracer("")

Creating spans

To create a span, you'll typically want it to be started as the current span.
def do_work():
with tracer.start_as_current_span("span-name") as span:
# do some work that 'span' will track
print("doing some work...")
# When the 'with' block goes out of scope, 'span' is closed for you
You can also use start_span to create a span without making it the current span. This is usually done to track concurrent or asynchronous operations.

Creating nested spans

If you have a distinct sub-operation you'd like to track as a part of another one, you can create span to represent the relationship:
def do_work():
with tracer.start_as_current_span("parent") as parent:
# do some work that 'parent' tracks
print("doing some work...")
# Create a nested span to track nested work
with tracer.start_as_current_span("child") as child:
# do some work that 'child' tracks
print("doing some nested work...")
# the nested span is closed when it's out of scope
# This span is also closed when it goes out of scope
When you view spans in a trace visualization tool, child will be tracked as a nested span under parent.

Creating spans with decorators

It's common to have a single spans track the execution of an entire function. In that scenario, there is a decorator you can use to reduce code:
def do_work():
print("doing some work...")
Use of the decorator is equivalent to creating the span inside do_work() and ending it when do_work() is finished.
To use the decorator, you must have a tracer instance available global to your function declaration.
If you need to add attributes or events then it's less convenient to use a decorator.

Get the current span

Sometimes it's helpful to access whatever the current spans is at a point in time so that you can enrich it with more information.
from opentelemetry import trace
current_span = trace.get_current_span()
# enrich 'current_span' with some information

Add attributes to a span

Attributes let you attach key/value pairs to a spans so it carries more information about the current operation that it's tracking.
from opentelemetry import trace
current_span = trace.get_current_span()
current_span.set_attribute("operation.value", 1)
current_span.set_attribute("", "Saying hello!")
current_span.set_attribute("operation.other-stuff", [1, 2, 3])
Notice above that the attributes have a specific prefix operation. When adding custom attributes, it's best practice to vendor your attributes (e.x. mycompany.) so that your attributes do not clash with semantic conventions.

Add semantic attributes

Semantic Attributes are pre-defined Attributes that are well-known naming conventions for common kinds of data. Using Semantic Attributes lets you normalize this kind of information across your systems. In the case of Phoenix, the OpenInference Semantic Conventions package provides a set of well-known attributes that are used to represent LLM application specific semantic conventions.
To use OpenInference Semantic Attributes in Python, ensure you have the semantic conventions package:
pip install openinference-semantic-conventions
Then you can use it in code:
from openinference.semconv.trace import SpanAttributes
// ...
current_span = trace.get_current_span()
current_span.set_attribute(SpanAttributes.INPUT_VALUE, "Hello world!")
current_span.set_attribute(SpanAttributes.LLM_MODEL_NAME, "gpt-3.5-turbo")

Adding events

An event is a human-readable message on a span that represents "something happening" during its lifetime. You can think of it as a primitive log.
from opentelemetry import trace
current_span = trace.get_current_span()
current_span.add_event("Gonna try it!")
# Do the thing
current_span.add_event("Did it!")

Set span status

from opentelemetry import trace
from opentelemetry.trace import Status, StatusCode
current_span = trace.get_current_span()
# something that might fail

Record exceptions in spans

It can be a good idea to record exceptions when they happen. It’s recommended to do this in conjunction with setting span status.
from opentelemetry import trace
from opentelemetry.trace import Status, StatusCode
current_span = trace.get_current_span()
# something that might fail
# Consider catching a more specific exception in your code
except Exception as ex: