test(debugger): ensure span error budgets are reasonable

manifests/java.yml

@@ -2695,6 +2695,7 @@ manifest:
         spring-boot-undertow: v1.38.0
         spring-boot-wildfly: v1.38.0
         uds-spring-boot: v1.38.0
+  tests/debugger/test_debugger_probe_budgets.py::Test_Debugger_Probe_Budgets::test_span_probe_expression_budgets: bug (DEBUG-3797)
   tests/debugger/test_debugger_probe_snapshot.py::Test_Debugger_Line_Probe_Snaphots:
     - weblog_declaration:
         "*": missing_feature

tests/debugger/test_debugger_probe_budgets.py

@@ -90,3 +90,52 @@ def test_log_line_budgets(self):
             assert 1 <= snapshots_with_captures <= 20, (
                 f"Expected 1-20 snapshot with captures, got {snapshots_with_captures} in {self.total_request_time} seconds"
             )
+
+    def setup_span_probe_expression_budgets(self):
+        self.initialize_weblog_remote_config()
+
+        probes = debugger.read_probes("probe_span_method_budgets_expression")
+        for probe in probes:
+            probe["id"] = debugger.generate_probe_id("decor")
+
+        self.set_probes(probes)
+        self.send_rc_probes()
+        self.wait_for_all_probes(statuses=["INSTALLED"])
+
+        start_time = time.time()
+        self.send_weblog_request("/debugger/budgets/1")
+        for _ in range(149):
+            self.send_weblog_request("/debugger/budgets/1", reset=False)
+        end_time = time.time()
+        self.total_request_time = end_time - start_time
+
+        # Allow time for the agent to receive data after the last request
+        time.sleep(2)
+
+    def test_span_probe_expression_budgets(self):
+        self.collect()
+        self.assert_setup_ok()
+        self.assert_rc_state_not_error()
+        self.assert_all_weblog_responses_ok()
+
+        # Count all snapshot entries emitted for the span probe.
+        # When a span probe's expression fails (e.g., "Cannot dereference field"),
+        # error logs should be rate-limited to at most 1 per second.
+        total_error_entries = 0
+        for _id in self.probe_ids:
+            if _id in self.probe_snapshots:
+                total_error_entries += len(self.probe_snapshots[_id])
+
+        # Verify at least one error entry was generated (probe actually fired and failed)
+        assert total_error_entries >= 1, (
+            f"Expected at least 1 error entry to verify the span probe expression error was logged, got 0"
+        )
+
+        # Error entries should be rate-limited to at most 1 per second.
+        # Allow a buffer for timing imprecision.
+        max_expected = int(self.total_request_time) + 5
+        assert total_error_entries <= max_expected, (
+            f"Expected at most {max_expected} error entries (1/sec budget for "
+            f"{self.total_request_time:.1f}s), got {total_error_entries}. "
+            f"Span probe expression error logging should be rate-limited."
+        )

tests/debugger/utils/probes/probe_span_method_budgets_expression.json

@@ -0,0 +1,46 @@
+[
+    {
+        "language": "",
+        "type": "",
+        "id": "",
+        "version": 0,
+        "targetSpan": "ACTIVE",
+        "decorations": [
+            {
+                "when": {
+                    "dsl": "",
+                    "json": {
+                        "gt": [
+                            {"ref": "loops"},
+                            0
+                        ]
+                    }
+                },
+                "tags": [
+                    {
+                        "name": "BudgetsTag",
+                        "value": {
+                            "template": null,
+                            "segments": [
+                                {
+                                    "dsl": "",
+                                    "json": {
+                                        "getmember": [
+                                            {"ref": "clientTracer"},
+                                            "nonExistentField"
+                                        ]
+                                    }
+                                }
+                            ]
+                        }
+                    }
+                ]
+            }
+        ],
+        "where": {
+            "typeName": "ACTUAL_TYPE_NAME",
+            "methodName": "Budgets",
+            "sourceFile": null
+        }
+    }
+]