test(integration): add e2e test for log rate limiting

Add integration tests that verify the rate-limited logging
infrastructure works end-to-end:

- rate_limited_log_count metric exists in the metrics output and is
  zero under normal (non-error) operation
- Normal balloon inflate/deflate does not trigger spurious suppression
  summary messages in the log output

Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>

Author: kalyazin

tests/integration_tests/functional/test_log_rate_limiting.py

@@ -0,0 +1,59 @@
+# Copyright 2026 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Tests for per-callsite log rate limiting.
+
+Validates that the rate-limited logging infrastructure is wired up correctly
+end-to-end: the rate_limited_log_count metric exists in the metrics output,
+and normal balloon operations (which use error_rate_limited! at some callsites)
+do not produce spurious suppression summaries under non-error conditions.
+"""
+
+
+def test_rate_limited_metric_exists(uvm_plain):
+    """
+    Verify that the rate_limited_log_count metric is present in the
+    metrics output and is zero under normal (non-error) operation.
+    """
+    microvm = uvm_plain
+    microvm.spawn()
+    microvm.basic_config()
+    microvm.start()
+
+    metrics = microvm.flush_metrics()
+
+    # The logger metrics should contain the new rate_limited_log_count field.
+    assert "logger" in metrics
+    assert "rate_limited_log_count" in metrics["logger"]
+    # Under normal operation no messages should be rate-limited.
+    assert metrics["logger"]["rate_limited_log_count"] == 0
+
+
+def test_no_spurious_suppression_in_logs(uvm_plain):
+    """
+    Verify that normal balloon inflate/deflate does not trigger rate
+    limiting suppression messages in the log output.
+    """
+    microvm = uvm_plain
+    microvm.spawn(log_show_level=True)
+    microvm.basic_config()
+    microvm.add_net_iface()
+
+    # Add a balloon device.
+    microvm.api.balloon.put(
+        amount_mib=0, deflate_on_oom=True, stats_polling_interval_s=0
+    )
+    microvm.start()
+
+    # Inflate and deflate — this exercises the balloon code paths that
+    # now use error_rate_limited!, but under normal operation none of
+    # the error paths should fire.
+    microvm.api.balloon.patch(amount_mib=64)
+    microvm.api.balloon.patch(amount_mib=0)
+
+    log_data = microvm.log_data
+    # No suppression summary should appear in normal operation.
+    assert "messages were suppressed at" not in log_data
+
+    # Verify metric is still zero.
+    metrics = microvm.flush_metrics()
+    assert metrics["logger"]["rate_limited_log_count"] == 0