feat: add process tags to traces

[wantsui]

What does this PR do?

The goal of AIDM-253 is to add process tags to the trace payloads.

After this gets merged, the next step is to add it for the other products.

To run the tests in docker

docker compose run --rm tracer-3.3 /bin/bash

Main tests:

bundle install --gemfile /app/gemfiles/ruby_3.3_rails8.gemfile
bundle exec rake compile
bundle exec rake test:core_with_rails
TEST_DATADOG_INTEGRATION=1 BUNDLE_GEMFILE=/app/gemfiles/ruby_3.3_rails8.gemfile bundle exec rspec spec/datadog/core/environment/process_spec.rb


bundle exec rspec spec/datadog/tracing/transport/trace_formatter_spec.rb
bundle exec rspec spec/datadog/core/tag_normalizer_spec.rb
bundle exec rspec spec/datadog/core/configuration/settings_spec.rb

Motivation:

We're trying to add process tags to various payloads so they can be used in different use cases.

Note I still want to try adding server type but I'll have to tackle that in a separate PR.

Change log entry

Yes. Adds process tags to trace payloads with the new environment variable: DD_EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED.

Additional Notes:

How to test the change?

[github-actions]

Thank you for updating Change log entry section 👏

^{Visited at: 2025-12-02 20:18:02 UTC}

[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 98.08%
• Total Coverage: 95.22% (+0.01%)

View detailed report

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 50d3392 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-12-04 03:26:05

Comparing candidate commit 50d3392 in PR branch add-process-tags-to-tracing with baseline commit 7243ac3 in branch master.

Found 0 performance improvements and 2 performance regressions! Performance is the same for 42 metrics, 2 unstable metrics.

scenario:error - error tracking, with_error=true - third_party only

• 🟥 throughput [-640.577op/s; -597.599op/s] or [-5.672%; -5.291%]

scenario:tracing - Propagation - Trace Context

• 🟥 throughput [-3650.334op/s; -3540.900op/s] or [-9.667%; -9.378%]

[github-actions]

Typing analysis

Note: Ignored files are excluded from the next sections.

Untyped methods

This PR introduces 2 partially typed methods. It increases the percentage of typed methods from 55.46% to 55.53% (+0.07%).

Partially typed methods (+2-0)

❌ Introduced:

sig/datadog/core/tag_normalizer.rbs:11
└── def self.normalize: (untyped original_value, ?remove_digit_start_char: bool) -> ::String
sig/datadog/core/tag_normalizer.rbs:13
└── def self.normalize_process_value: (untyped value) -> ::String

If you believe a method or an attribute is rightfully untyped or partially typed, you can add # untyped:accept to the end of the line to remove it from the stats.

[p-datadog]

This one is even more of a pickle:

big% ruby -e 'puts $0; sleep 1000000000'
-e

[p-datadog]

I added a commit changing before/after to around for the $0 override.

[marcotc]

I recommend applying the renamming suggested by @Strech in 5cae372#r2584467486, but all else is good!