fix(runtime metrics): ensure DD_TAGS are added to runtime metrics [backport 1.16] (#6274)

Backport 09956e4 from #6271 to 1.16.

This is a fix for a bug found in testing #6121.

The tests in #6121 were testing the individual tag collectors, but not
the `RuntimeCollectorsIterator` which will filter out any undefined
tags.

The fix needed was to remove the tag filter from the `RuntimeTags`
iterator. This means any tags emitted by `TracerTagCollector` or
`PlatformTagCollector` will be included, instead of specifying an
explicit allow list.

Tests were added for the `RuntimeTags` iterator to ensure the expected
behavior is followed for the new behavior.

No changelog entry is needed since this fix is being added to 1.16.0rc1
before the release.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: Brett Langdon <[email protected]>

Author: github-actions[bot]

ddtrace/internal/runtime/constants.py

@@ -25,9 +25,3 @@
 LANG_VERSION = "lang_version"
 LANG = "lang"
 TRACER_VERSION = "tracer_version"
-
-TRACER_TAGS = set([SERVICE, ENV])
-
-PLATFORM_TAGS = set([LANG_INTERPRETER, LANG_VERSION, LANG, TRACER_VERSION])
-
-DEFAULT_RUNTIME_TAGS = TRACER_TAGS | PLATFORM_TAGS

ddtrace/internal/runtime/runtime_metrics.py

@@ -14,7 +14,6 @@
 from ..dogstatsd import get_dogstatsd_client
 from ..logger import get_logger
 from .constants import DEFAULT_RUNTIME_METRICS
-from .constants import DEFAULT_RUNTIME_TAGS
 from .metric_collectors import GCRuntimeMetricCollector
 from .metric_collectors import PSUtilRuntimeMetricCollector
 from .tag_collectors import PlatformTagCollector
@@ -42,7 +41,8 @@ def __repr__(self):
 
 
 class RuntimeTags(RuntimeCollectorsIterable):
-    ENABLED = DEFAULT_RUNTIME_TAGS
+    # DEV: `None` means to allow all tags generated by PlatformTagCollector and TracerTagCollector
+    ENABLED = None
     COLLECTORS = [
         PlatformTagCollector,
         TracerTagCollector,

tests/tracer/runtime/test_runtime_metrics.py

@@ -3,6 +3,7 @@
 import time
 
 import mock
+import pytest
 
 from ddtrace.ext import SpanTypes
 from ddtrace.internal.runtime.constants import DEFAULT_RUNTIME_METRICS
@@ -69,6 +70,64 @@ def filter_only_env_tags(tags):
                 assert tags == [("env", "staging.dog")]
 
 
+@pytest.mark.subprocess(env={})
+def test_runtime_tags_empty():
+    from ddtrace.internal.runtime.runtime_metrics import RuntimeTags
+
+    tags = list(RuntimeTags())
+    assert len(tags) == 4
+
+    tags = dict(tags)
+    assert set(tags.keys()) == set(["lang", "lang_interpreter", "lang_version", "tracer_version"])
+
+
+@pytest.mark.subprocess(env={"DD_SERVICE": "my-service", "DD_ENV": "test-env", "DD_VERSION": "1.2.3"})
+def test_runtime_tags_usm():
+    from ddtrace.internal.runtime.runtime_metrics import RuntimeTags
+
+    tags = list(RuntimeTags())
+    assert len(tags) == 7, tags
+
+    tags = dict(tags)
+    assert set(tags.keys()) == set(
+        ["lang", "lang_interpreter", "lang_version", "tracer_version", "service", "version", "env"]
+    )
+    assert tags["service"] == "my-service"
+    assert tags["env"] == "test-env"
+    assert tags["version"] == "1.2.3"
+
+
+@pytest.mark.subprocess(env={"DD_TAGS": "version:1.2.3,custom:tag,test:key", "DD_VERSION": "4.5.6"})
+def test_runtime_tags_dd_tags():
+    from ddtrace.internal.runtime.runtime_metrics import RuntimeTags
+
+    tags = list(RuntimeTags())
+    assert len(tags) == 7, tags
+
+    tags = dict(tags)
+    assert set(tags.keys()) == set(
+        ["lang", "lang_interpreter", "lang_version", "tracer_version", "version", "custom", "test"]
+    )
+    assert tags["custom"] == "tag"
+    assert tags["test"] == "key"
+    assert tags["version"] == "4.5.6"
+
+
+@pytest.mark.subprocess()
+def test_runtime_tags_manual_tracer_tags():
+    from ddtrace import tracer
+    from ddtrace.internal.runtime.runtime_metrics import RuntimeTags
+
+    tracer.set_tags({"manual": "tag"})
+
+    tags = list(RuntimeTags())
+    assert len(tags) == 5, tags
+
+    tags = dict(tags)
+    assert set(tags.keys()) == set(["lang", "lang_interpreter", "lang_version", "tracer_version", "manual"])
+    assert tags["manual"] == "tag"
+
+
 class TestRuntimeMetrics(BaseTestCase):
     def test_all_metrics(self):
         metrics = set([k for (k, v) in RuntimeMetrics()])

tests/tracer/runtime/test_tag_collectors.py

@@ -1,13 +1,12 @@
 import pytest
 
-from ddtrace.internal.runtime import constants
 from ddtrace.internal.runtime import tag_collectors
 
 
 def test_values():
     ptc = tag_collectors.PlatformTagCollector()
     values = dict(ptc.collect())
-    assert constants.PLATFORM_TAGS == set(values.keys())
+    assert set(["lang", "lang_interpreter", "lang_version", "tracer_version"]) == set(values.keys())
 
 
 @pytest.mark.subprocess(