FiddlerClient

FiddlerClient

The main client for instrumenting Generative AI applications with Fiddler observability.

This client configures and manages the OpenTelemetry tracer that sends telemetry data to the Fiddler platform for monitoring, analysis, and debugging of your AI agents and workflows.

Parameters

Parameter	Type	Required	Default	Description
api_key	str	✓	-	The API key for authenticating with the Fiddler backend.
application_id	str	✓	-	The unique identifier (UUID4) for the application.
url	str	✓	-	The base URL for your Fiddler instance. This is specific to your deployment, whether hosted, VPC-deployed, on-premise, or local development (e.g., https://your-instance.fiddler.ai, http://localhost:4318).
console_tracer	bool	✗	False	If True, traces will be printed to the console instead of being sent to the Fiddler backend. Useful for debugging.
span_limits	SpanLimits | None	✗	a restrictive set of internal limits (32 events	Configuration for span limits, such as the maximum number of attributes or events. 2048 char limit).
sampler	sampling.Sampler | None	✗	None, which uses the parent-based always-on Ope	The sampler for deciding which spans to record. which uses the parent-based always-on OpenTelemetry sampler (100% sampling).
compression	Compression	✗	Compression.Gzip (recommended for production	The compression for exporting traces. Can be Compression.Gzip, Compression.Deflate, or Compression.NoCompression. Defaults to Compression.Gzip (recommended for production).
jsonl_capture_enabled	bool	✗	False	Whether to enable JSONL capture of trace data. When enabled, all span data will be captured and saved to a JSONL file in OpenTelemetry format for offline analysis.
jsonl_file_path	str	✗	“fiddler_trace_data.jsonl”	Path to the JSONL file where trace data will be saved. Only used when jsonl_capture_enabled is True. Defaults to “fiddler_trace_data.jsonl”.

Raises

ValueError – If application_id is not a valid UUID4 or if the url is not a valid HTTP/HTTPS URL.

Examples

Basic connection to your Fiddler instance:

client = FiddlerClient(
    api_key='YOUR_API_KEY',
    application_id='YOUR_APPLICATION_ID',
    url='https://your-instance.fiddler.ai',
)

High-volume applications with custom configuration:

from opentelemetry.sdk.trace import SpanLimits, sampling
from opentelemetry.exporter.otlp.proto.http.trace_exporter import Compression

client = FiddlerClient(
    api_key='YOUR_API_KEY',
    application_id='YOUR_APPLICATION_ID',
    url='https://your-instance.fiddler.ai',
    span_limits=SpanLimits(max_span_attributes=64),
    sampler=sampling.TraceIdRatioBased(0.1),  # Sample 10% of traces
    compression=Compression.Gzip,
)

Local development with console output:

client = FiddlerClient(
    api_key='dev-key',
    application_id='00000000-0000-0000-0000-000000000000',
    url='http://localhost:4318',
    console_tracer=True,  # Print traces to console for debugging
)

get_tracer_provider()

Gets the OpenTelemetry TracerProvider instance.

Initializes the provider on the first call.

Returns

The configured OpenTelemetry TracerProvider.

Return type: TracerProvider

Raises

RuntimeError – If tracer provider initialization fails.

update_resource()

Updates the OpenTelemetry resource with additional attributes.

Use this to add metadata that applies to all spans, such as version numbers or environment names.

Must be called before get_tracer() is invoked.

Parameters

Parameter	Type	Required	Default	Description
attributes	dict[str, Any]	✓	-	Key-value pairs to add to the resource.

Raises

ValueError – If the tracer has already been initialized. Return type: None

Examples

from fiddler_langgraph import FiddlerClient
client = FiddlerClient(api_key='...', application_id='...', url='https://your-instance.fiddler.ai')
client.update_resource({'service.version': '1.2.3'})

get_tracer()

Returns an OpenTelemetry tracer instance for creating spans.

Initializes the tracer on the first call. This is the primary method for developers to get a tracer for custom instrumentation.

Returns

OpenTelemetry tracer instance.

Return type: trace.Tracer

Raises

RuntimeError – If tracer initialization fails.

Examples

from fiddler_langgraph import FiddlerClient
client = FiddlerClient(api_key='...', application_id='...', url='https://your-instance.fiddler.ai')
tracer = client.get_tracer()
with tracer.start_as_current_span('my-operation'):
    print('Doing some work...')