feat(exporter): implement subprocess execution with active stall watchdog and TCP metrics (#26)

- Replace in-process iperf3 C binding with subprocess execution
- Add active I/O stall detection and connect-timeout
- Expose TCP retransmissions, mean RTT (ms), and exporter cycle timestamp
- Upgrade Dockerfile to Python 3.12 running as non-root user (nobody)
- Fix testTimeout/testDuration environment variable mapping in Helm chart
- Remove dead TrueCharts prometheus-operator chart dependency
- Add unit tests for exporter metric parsing and stall handling
- Switch tooling from devbox to mise

Co-authored-by: Malarbase <malarbase@gmail.com>

exporter/test_exporter.py

@@ -0,0 +1,111 @@
+import os
+import sys
+import unittest
+import json
+from unittest.mock import patch, MagicMock
+
+import importlib.util
+
+spec = importlib.util.spec_from_file_location("exporter_mod", os.path.join(os.path.dirname(__file__), "exporter.py"))
+exporter = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(exporter)
+
+class TestExporter(unittest.TestCase):
+
+    def setUp(self):
+        self.source = "node-a"
+        self.dest = "node-b"
+        self.labels = {'source_node': self.source, 'destination_node': self.dest, 'protocol': 'tcp'}
+        self.udp_labels = {'source_node': self.source, 'destination_node': self.dest, 'protocol': 'udp'}
+
+    def test_parse_tcp_success(self):
+        tcp_json = {
+            "end": {
+                "streams": [
+                    {
+                        "sender": {
+                            "mean_rtt": 250,  # 250 microseconds = 0.25 ms
+                            "retransmits": 3
+                        }
+                    }
+                ],
+                "sum_sent": {
+                    "seconds": 5.0,
+                    "bytes": 50000000,
+                    "bits_per_second": 80000000.0,
+                    "retransmits": 3
+                },
+                "sum_received": {
+                    "seconds": 5.0,
+                    "bytes": 49000000,
+                    "bits_per_second": 78400000.0
+                }
+            }
+        }
+
+        exporter.parse_and_publish_metrics(tcp_json, self.source, self.dest, 'tcp')
+
+        self.assertEqual(exporter.IPERF_TEST_SUCCESS.labels(**self.labels)._value.get(), 1)
+        self.assertAlmostEqual(exporter.IPERF_BANDWIDTH_MBPS.labels(**self.labels)._value.get(), 78.4)
+        self.assertEqual(exporter.IPERF_TCP_RETRANSMITS.labels(**self.labels)._value.get(), 3)
+        self.assertAlmostEqual(exporter.IPERF_TCP_RTT_MS.labels(**self.labels)._value.get(), 0.25)
+        self.assertEqual(exporter.IPERF_TEST_DURATION_SECONDS.labels(**self.labels)._value.get(), 5.0)
+        self.assertEqual(exporter.IPERF_JITTER_MS.labels(**self.labels)._value.get(), 0)
+
+    def test_parse_udp_success(self):
+        udp_json = {
+            "end": {
+                "sum": {
+                    "seconds": 5.0,
+                    "bytes": 1000000,
+                    "bits_per_second": 1600000.0,
+                    "jitter_ms": 1.25,
+                    "packets": 1000,
+                    "lost_packets": 2
+                }
+            }
+        }
+
+        exporter.parse_and_publish_metrics(udp_json, self.source, self.dest, 'udp')
+
+        self.assertEqual(exporter.IPERF_TEST_SUCCESS.labels(**self.udp_labels)._value.get(), 1)
+        self.assertAlmostEqual(exporter.IPERF_BANDWIDTH_MBPS.labels(**self.udp_labels)._value.get(), 1.6)
+        self.assertEqual(exporter.IPERF_JITTER_MS.labels(**self.udp_labels)._value.get(), 1.25)
+        self.assertEqual(exporter.IPERF_PACKETS_TOTAL.labels(**self.udp_labels)._value.get(), 1000)
+        self.assertEqual(exporter.IPERF_LOST_PACKETS.labels(**self.udp_labels)._value.get(), 2)
+        self.assertEqual(exporter.IPERF_TCP_RETRANSMITS.labels(**self.udp_labels)._value.get(), 0)
+
+    def test_parse_error_result(self):
+        err_json = {
+            "error": "error - unable to connect to server: Connection timed out"
+        }
+
+        exporter.parse_and_publish_metrics(err_json, self.source, self.dest, 'tcp')
+
+        self.assertEqual(exporter.IPERF_TEST_SUCCESS.labels(**self.labels)._value.get(), 0)
+        self.assertEqual(exporter.IPERF_BANDWIDTH_MBPS.labels(**self.labels)._value.get(), 0)
+        self.assertEqual(exporter.IPERF_TCP_RETRANSMITS.labels(**self.labels)._value.get(), 0)
+        self.assertEqual(exporter.IPERF_TCP_RTT_MS.labels(**self.labels)._value.get(), 0)
+
+    @patch("subprocess.Popen")
+    def test_stall_exception_raised_on_stall(self, mock_popen):
+        # Simulate a process that never terminates and produces no I/O progress
+        fake_proc = MagicMock()
+        fake_proc.poll.return_value = None  # Process is running
+        fake_proc.pid = 999999  # Non-existent PID to simulate no /proc IO advancement
+        mock_popen.return_value = fake_proc
+
+        with self.assertRaises(exporter.IperfTimeoutException):
+            exporter.execute_iperf_test(
+                server_ip="127.0.0.1",
+                server_port=5201,
+                protocol="tcp",
+                duration=1,
+                connect_timeout_ms=500,
+                stall_threshold_sec=1,
+            )
+
+        fake_proc.kill.assert_called()
+
+if __name__ == '__main__':
+    unittest.main()