test(metrics): add integration tests for id and properties

Cover the emitted metrics line shape, which the unit tests cannot reach
since they exercise the serializer in isolation rather than a running
microVM. Assert each combination of the two opt-in fields: neither set,
`emit_id` alone, `properties` alone, and both together, checking that
the `id` and `properties` keys appear (or not) and carry the configured
values.

Signed-off-by: Jay Chung <jaehoc@amazon.com>

Author: not4s

tests/integration_tests/functional/test_metrics.py

@@ -3,6 +3,7 @@
 """Tests the metrics system."""
 
 import os
+from pathlib import Path
 
 import host_tools.drive as drive_tools
 from framework.artifacts import GUEST_KERNEL_DEFAULT, pin_guest_kernel
@@ -23,6 +24,88 @@ def test_flush_metrics(uvm):
     validate_fc_metrics(metrics)
 
 
+def _configure_metrics_via_api(microvm, **kwargs):
+    """Configure metrics through the API rather than the `--metrics-path` CLI
+    option (the two ways of initializing metrics are mutually exclusive), and
+    wire up the host-side metrics file so the line can be read back."""
+    microvm.spawn(metrics_path=None)
+    microvm.basic_config()
+
+    metrics_path = Path(microvm.path) / "metrics.ndjson"
+    metrics_path.touch()
+    microvm.metrics_file = metrics_path
+
+    microvm.api.metrics.put(
+        metrics_path=microvm.create_jailed_resource(metrics_path), **kwargs
+    )
+    microvm.start()
+
+
+@pin_guest_kernel(GUEST_KERNEL_DEFAULT)
+def test_metrics_default_shape(uvm):
+    """
+    Check that, with neither field configured, a metrics line carries neither
+    the top-level `id` field nor the `properties` map.
+    """
+    microvm = uvm
+    microvm.spawn()
+    microvm.basic_config()
+    microvm.start()
+
+    metrics = microvm.flush_metrics()
+    validate_fc_metrics(metrics)
+    assert "id" not in metrics
+    assert "properties" not in metrics
+
+
+@pin_guest_kernel(GUEST_KERNEL_DEFAULT)
+def test_metrics_emit_id(uvm):
+    """
+    Check that `emit_id` makes every metrics line carry the top-level `id` field
+    holding the microVM instance id, without requiring custom properties.
+    """
+    microvm = uvm
+    _configure_metrics_via_api(microvm, emit_id=True)
+
+    metrics = microvm.flush_metrics()
+    validate_fc_metrics(metrics)
+    assert metrics["id"] == microvm.id
+    assert "properties" not in metrics
+
+
+@pin_guest_kernel(GUEST_KERNEL_DEFAULT)
+def test_metrics_with_properties(uvm):
+    """
+    Check that configuring custom properties via `PUT /metrics` makes every
+    metrics line carry the operator-defined `properties` map, without emitting
+    the `id` field when `emit_id` is not set.
+    """
+    microvm = uvm
+    properties = {"customer_id": "1234", "bundle_id": "fn-abc"}
+    _configure_metrics_via_api(microvm, properties=properties)
+
+    metrics = microvm.flush_metrics()
+    validate_fc_metrics(metrics)
+    assert metrics["properties"] == properties
+    assert "id" not in metrics
+
+
+@pin_guest_kernel(GUEST_KERNEL_DEFAULT)
+def test_metrics_emit_id_and_properties(uvm):
+    """
+    Check that `emit_id` and custom properties can be configured together, so a
+    metrics line carries both the top-level `id` field and the `properties` map.
+    """
+    microvm = uvm
+    properties = {"customer_id": "1234", "bundle_id": "fn-abc"}
+    _configure_metrics_via_api(microvm, emit_id=True, properties=properties)
+
+    metrics = microvm.flush_metrics()
+    validate_fc_metrics(metrics)
+    assert metrics["id"] == microvm.id
+    assert metrics["properties"] == properties
+
+
 @pin_guest_kernel(GUEST_KERNEL_DEFAULT)
 def test_net_metrics(uvm):
     """