For agent URL configuration, consider empty environment variables as unset

[xlamorlette-datadog]

Description

When reading the DD_TRACE_AGENT_URL, DD_AGENT_HOST and DD_TRACE_AGENT_PORT environment variables for the configuration of the agent, consider empty values as unset.

Motivation

This was discovered when activating the handling of IPv6 agent host addresses in System Tests. See the error:

unable to initialize tracer:Datadog Agent URL is missing the "://" separator: ""

Actually, this does not come from the newly implemented handling of IPv6 agent host addresses, this was a bug already present before.

Additional Notes

Jira ticket: IDMPL-760 [C++ Tracer] Bug: empty environment variables for agent configuration not handled correctly

performance/ignore-performance-regression: We get very often high values for BM_TraceID_ParseHex whereas the relative code has not been touched:

[STDERR] Fail on regression  | FAIL! Metric MetricName.EXECUTION_TIME in scenario:BM_TraceID_ParseHex/64bit has regression +32.48%, larger than threshold 5.00%.
[STDERR] Fail on regression  | FAIL! Metric MetricName.EXECUTION_TIME in scenario:BM_TraceID_ParseHex/128bit has regression +40.50%, larger than threshold 5.00%.

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-08-12 14:33:41

Comparing candidate commit af3dcdb in PR branch xlamorlette/fix-empty-agent-env-variables with baseline commit 2e86335 in branch main.

Found 0 performance improvements and 2 performance regressions! Performance is the same for 6 metrics, 0 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

scenario:BM_TraceID_ParseHex/128bit

• 🟥 execution_time [+49.771ns; +49.956ns] or [+40.504%; +40.656%]

scenario:BM_TraceID_ParseHex/64bit

• 🟥 execution_time [+22.502ns; +22.517ns] or [+32.484%; +32.505%]

[datadog-prod-us1-3]

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⚠️ Warnings

🚦 1 Pipeline job failed

DataDog/apm-reliability/dd-trace-cpp | check-big-regressions     

ℹ️ Info

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 84.48% (+0.01%)

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