chore(dbm): add injection mode environment variable

ddtrace/settings/database_monitoring.py

@@ -0,0 +1,17 @@
+from envier import En
+from envier import validators
+
+
+class DatabaseMonitoringConfig(En):
+    __prefix__ = "dd_trace"
+
+    injection_mode = En.v(
+        str,
+        "sql_comment_injection_mode",
+        default="disabled",
+        help="Valid Injection Modes: disabled, service, and full",
+        validator=validators.choice(["disabled", "full", "service"]),
+    )
+
+
+config = DatabaseMonitoringConfig()

tests/internal/test_database_monitoring.py

@@ -0,0 +1,29 @@
+import pytest
+
+from ddtrace.settings import database_monitoring
+from tests.utils import override_env
+
+
+def test_injection_mode_configuration():
+    # Ensure Database Monitoring support is disabled by default
+    # TODO: Enable DBM support by default
+    assert database_monitoring.config.injection_mode == "disabled"
+
+    # Ensure service is a valid injection mode
+    with override_env(dict(DD_TRACE_SQL_COMMENT_INJECTION_MODE="service")):
+        config = database_monitoring.DatabaseMonitoringConfig()
+        assert config.injection_mode == "service"
+
+    # Ensure full is a valid injection mode
+    with override_env(dict(DD_TRACE_SQL_COMMENT_INJECTION_MODE="full")):
+        config = database_monitoring.DatabaseMonitoringConfig()
+        assert config.injection_mode == "full"
+
+    # Ensure an invalid injection mode raises a ValueError
+    with override_env(dict(DD_TRACE_SQL_COMMENT_INJECTION_MODE="notaninjectionmode")):
+        with pytest.raises(ValueError) as excinfo:
+            database_monitoring.DatabaseMonitoringConfig()
+    assert (
+        excinfo.value.args[0] == "Invalid value for environment variable DD_TRACE_SQL_COMMENT_INJECTION_MODE: "
+        "value must be one of ['disabled', 'full', 'service']"
+    )