Installation failure#

ModuleNotFoundError: No module named 'Cython'

pip is failing to install ddtrace and complaining about a missing module (Cython). pip>=18 is required to properly install ddtrace package.

Check which version of pip you are using with pip --version.

Consider upgrading pip via pip install -U pip>=18.

Traces not showing up in the app#

The most common reason for traces not being received by Datadog is an agent communication issue:

  • Ensure the Datadog agent is running and reachable over the network if not on the same host.

  • Ensure that ddtrace is configured with the hostname and port of the agent. See Configuration for the configuration variables.

To verify that a connection can be made to the agent with your environment variable configurations run the command ddtrace-run --info.

Failed to send traces… ConnectionRefusedError#

Failed to send traces to Datadog Agent...: ConnectionRefusedError(111, 'Connection refused')

The most common error is a connection error. If you’re experiencing a connection error, please make sure you’ve followed the setup for your particular environment so that the tracer and Datadog agent are configured properly to connect, and that the Datadog agent is running:

If the above doesn’t fix your issue, the Datadog Agent also has a limit to the number of connections it can receive. This can be configured with the instructions here:

Service, Env, or Version not set#

The service, env, and version tags are reserved tags in Datadog that allow unique capabilities in the Datadog UI for correlating and viewing data. In order to have all of the features Datadog provides, we’d recommend setting these tags.

The service tag is used for the scoping of application specific data across metrics, traces, and logs. If a service tag is not provided for the tracer, traces and trace metrics will appear under the name of the instrumented integration, e.g. flask for a Flask application.

The env tag is used for the scoping of the application’s data to a specific environment, e.g. env:prod vs env:dev.

For more information about the version tag please see:

To set service, env, and version properly for your environment, please see:

Root span is missing error details#

If an error is raised during the execution of instrumented code, any span from instrumented code which does not handle the exception will include error details (error flag, message, type, traceback).

However, if the instrumented code for a span handles the exception, that span will not include error details as the exception is not raised from the call stack of the span’s execution context.

This can be a problem for users who want to see error details from a child span in the root span of a trace. An example of this is when an error is raised during the execution of view code, subsequently handled by the web framework in order to return an error page, the error details from the span for an instrumented view will not be included in the root span for the request.

While this is default behavior for integrations, users can add a trace filter to propagate the error details up to the root span:

from ddtrace import Span, tracer
from ddtrace.filters import TraceFilter

class ErrorFilter(TraceFilter):
  def process_trace(self, trace):
      # Find first child span with an error and copy its error details to root span
      if not trace:
          return trace

      local_root = trace[0]

      for span in trace[1:]:
          if span.error == 1:  # or any other conditional for finding the relevant child span
              local_root.error = 1
                  "error.msg": span.get_tag("error.msg"),
                  "error.type": span.get_tag("error.type"),
                  "error.stack": span.get_tag("error.stack"),

      return trace

tracer.configure(settings={'FILTERS': [ErrorFilter()]})

Still having issues?#

If none of the above was able to resolve the issue then please reach out to Datadog support at Or view the other support options listed here: