IQ.Pilot Prebuilt Release @ ab07000

cereal/messaging/__init__.py

@@ -0,0 +1,269 @@
+# must be built with scons
+from msgq import fake_event_handle, drain_sock_raw, MultiplePublishersError, IpcError, \
+                 Context, Poller, SubSocket, PubSocket, SocketEventHandle, toggle_fake_events, \
+                 set_fake_prefix, get_fake_prefix, delete_fake_prefix, wait_for_one_event
+import msgq
+import os
+import capnp
+import time
+
+from typing import Optional, List, Union, Dict
+
+from cereal import log
+from cereal.services import SERVICE_LIST
+from openpilot.common.utils import MovingAverage
+
+NO_TRAVERSAL_LIMIT = 2**64-1
+
+
+def pub_sock(endpoint: str) -> PubSocket:
+  service = SERVICE_LIST.get(endpoint)
+  segment_size = service.queue_size if service else 0
+  return msgq.pub_sock(endpoint, segment_size)
+
+
+def sub_sock(endpoint: str, poller: Optional[Poller] = None, addr: str = "127.0.0.1",
+             conflate: bool = False, timeout: Optional[int] = None) -> SubSocket:
+  service = SERVICE_LIST.get(endpoint)
+  segment_size = service.queue_size if service else 0
+  return msgq.sub_sock(endpoint, poller=poller, addr=addr, conflate=conflate,
+                       timeout=timeout, segment_size=segment_size)
+
+
+def reset_context():
+  msgq.context = Context()
+
+
+def log_from_bytes(dat: bytes, struct: capnp.lib.capnp._StructModule = log.Event) -> capnp.lib.capnp._DynamicStructReader:
+  with struct.from_bytes(dat, traversal_limit_in_words=NO_TRAVERSAL_LIMIT) as msg:
+    return msg
+
+
+def new_message(service: Optional[str], size: Optional[int] = None, **kwargs) -> capnp.lib.capnp._DynamicStructBuilder:
+  args = {
+    'valid': False,
+    'logMonoTime': int(time.monotonic() * 1e9),
+    **kwargs
+  }
+  dat = log.Event.new_message(**args)
+  if service is not None:
+    if size is None:
+      dat.init(service)
+    else:
+      dat.init(service, size)
+  return dat
+
+
+def drain_sock(sock: SubSocket, wait_for_one: bool = False) -> List[capnp.lib.capnp._DynamicStructReader]:
+  """Receive all message currently available on the queue"""
+  msgs = drain_sock_raw(sock, wait_for_one=wait_for_one)
+  return [log_from_bytes(m) for m in msgs]
+
+
+# TODO: print when we drop packets?
+def recv_sock(sock: SubSocket, wait: bool = False) -> Optional[capnp.lib.capnp._DynamicStructReader]:
+  """Same as drain sock, but only returns latest message. Consider using conflate instead."""
+  dat = None
+
+  while 1:
+    if wait and dat is None:
+      recv = sock.receive()
+    else:
+      recv = sock.receive(non_blocking=True)
+
+    if recv is None:  # Timeout hit
+      break
+
+    dat = recv
+
+  if dat is not None:
+    dat = log_from_bytes(dat)
+
+  return dat
+
+
+def recv_one(sock: SubSocket) -> Optional[capnp.lib.capnp._DynamicStructReader]:
+  dat = sock.receive()
+  if dat is not None:
+    dat = log_from_bytes(dat)
+  return dat
+
+
+def recv_one_or_none(sock: SubSocket) -> Optional[capnp.lib.capnp._DynamicStructReader]:
+  dat = sock.receive(non_blocking=True)
+  if dat is not None:
+    dat = log_from_bytes(dat)
+  return dat
+
+
+def recv_one_retry(sock: SubSocket) -> capnp.lib.capnp._DynamicStructReader:
+  """Keep receiving until we get a message"""
+  while True:
+    dat = sock.receive()
+    if dat is not None:
+      return log_from_bytes(dat)
+
+
+class FrequencyTracker:
+  def __init__(self, service_freq: float, update_freq: float, is_poll: bool):
+    freq = max(min(service_freq, update_freq), 1.)
+    if is_poll:
+      min_freq = max_freq = freq
+    else:
+      max_freq = min(freq, update_freq)
+      if service_freq >= 2 * update_freq:
+        min_freq = update_freq
+      elif update_freq >= 2* service_freq:
+        min_freq = freq
+      else:
+        min_freq = min(freq, freq / 2.)
+
+    self.min_freq = min_freq * 0.8
+    self.max_freq = max_freq * 1.2
+    self.avg_dt = MovingAverage(int(10 * freq))
+    self.recent_avg_dt = MovingAverage(int(freq))
+    self.prev_time = 0.0
+
+  def record_recv_time(self, cur_time: float) -> None:
+    # TODO: Handle case where cur_time is less than prev_time
+    if self.prev_time > 1e-5:
+      dt = cur_time - self.prev_time
+
+      self.avg_dt.add_value(dt)
+      self.recent_avg_dt.add_value(dt)
+
+    self.prev_time = cur_time
+
+  @property
+  def valid(self) -> bool:
+    if self.avg_dt.count == 0:
+      return False
+
+    avg_freq = 1.0 / self.avg_dt.get_average()
+    if self.min_freq <= avg_freq <= self.max_freq:
+      return True
+
+    avg_freq_recent = 1.0 / self.recent_avg_dt.get_average()
+    return self.min_freq <= avg_freq_recent <= self.max_freq
+
+
+class SubMaster:
+  def __init__(self, services: List[str], poll: Optional[str] = None,
+               ignore_alive: Optional[List[str]] = None, ignore_avg_freq: Optional[List[str]] = None,
+               ignore_valid: Optional[List[str]] = None, addr: str = "127.0.0.1", frequency: Optional[float] = None):
+    self.frame = -1
+    self.services = services
+    self.seen = {s: False for s in services}
+    self.updated = {s: False for s in services}
+    self.recv_time = {s: 0. for s in services}
+    self.recv_frame = {s: 0 for s in services}
+    self.sock = {}
+    self.data = {}
+    self.logMonoTime = {s: 0 for s in services}
+
+    # zero-frequency / on-demand services are always alive and presumed valid; all others must pass checks
+    on_demand = {s: SERVICE_LIST[s].frequency <= 1e-5 for s in services}
+    self.static_freq_services = set(s for s in services if not on_demand[s])
+    self.alive = {s: on_demand[s] for s in services}
+    self.freq_ok = {s: on_demand[s] for s in services}
+    self.valid = {s: on_demand[s] for s in services}
+
+    self.freq_tracker: Dict[str, FrequencyTracker] = {}
+    self.poller = Poller()
+    polled_services = set([poll, ] if poll is not None else services)
+    self.non_polled_services = set(services) - polled_services
+
+    self.ignore_average_freq = [] if ignore_avg_freq is None else ignore_avg_freq
+    self.ignore_alive = [] if ignore_alive is None else ignore_alive
+    self.ignore_valid = [] if ignore_valid is None else ignore_valid
+
+    self.simulation = bool(int(os.getenv("SIMULATION", "0")))
+
+    # if freq and poll aren't specified, assume the max to be conservative
+    assert frequency is None or poll is None, "Do not specify 'frequency' - frequency of the polled service will be used."
+    self.update_freq = frequency or max([SERVICE_LIST[s].frequency for s in polled_services])
+
+    for s in services:
+      p = self.poller if s not in self.non_polled_services else None
+      self.sock[s] = sub_sock(s, poller=p, addr=addr, conflate=True)
+
+      try:
+        data = new_message(s)
+      except capnp.lib.capnp.KjException:
+        data = new_message(s, 0) # lists
+
+      self.data[s] = getattr(data.as_reader(), s)
+      self.freq_tracker[s] = FrequencyTracker(SERVICE_LIST[s].frequency, self.update_freq, s == poll)
+
+  def __getitem__(self, s: str) -> capnp.lib.capnp._DynamicStructReader:
+    return self.data[s]
+
+  def _check_avg_freq(self, s: str) -> bool:
+    return SERVICE_LIST[s].frequency > 0.99 and (s not in self.ignore_average_freq) and (s not in self.ignore_alive)
+
+  def update(self, timeout: int = 100) -> None:
+    msgs = []
+    for sock in self.poller.poll(timeout):
+      msgs.append(recv_one_or_none(sock))
+
+    # non-blocking receive for non-polled sockets
+    for s in self.non_polled_services:
+      msgs.append(recv_one_or_none(self.sock[s]))
+    self.update_msgs(time.monotonic(), msgs)
+
+  def update_msgs(self, cur_time: float, msgs: List[capnp.lib.capnp._DynamicStructReader]) -> None:
+    self.frame += 1
+    self.updated = dict.fromkeys(self.services, False)
+    for msg in msgs:
+      if msg is None:
+        continue
+
+      s = msg.which()
+      self.seen[s] = True
+      self.updated[s] = True
+
+      self.freq_tracker[s].record_recv_time(cur_time)
+      self.recv_time[s] = cur_time
+      self.recv_frame[s] = self.frame
+      self.data[s] = getattr(msg, s)
+      self.logMonoTime[s] = msg.logMonoTime
+      self.valid[s] = msg.valid
+
+    for s in self.static_freq_services:
+      # alive if delay is within 10x the expected frequency; checks relaxed in simulator
+      self.alive[s] = (cur_time - self.recv_time[s]) < (10. / SERVICE_LIST[s].frequency) or (self.seen[s] and self.simulation)
+      self.freq_ok[s] = self.freq_tracker[s].valid or self.simulation
+
+  def all_alive(self, service_list: Optional[List[str]] = None) -> bool:
+    return all(self.alive[s] for s in (service_list or self.services) if s not in self.ignore_alive)
+
+  def all_freq_ok(self, service_list: Optional[List[str]] = None) -> bool:
+    return all(self.freq_ok[s] for s in (service_list or self.services) if self._check_avg_freq(s))
+
+  def all_valid(self, service_list: Optional[List[str]] = None) -> bool:
+    return all(self.valid[s] for s in (service_list or self.services) if s not in self.ignore_valid)
+
+  def all_checks(self, service_list: Optional[List[str]] = None) -> bool:
+    return self.all_alive(service_list) and self.all_freq_ok(service_list) and self.all_valid(service_list)
+
+
+class PubMaster:
+  def __init__(self, services: List[str]):
+    self.sock = {}
+    for s in services:
+      self.sock[s] = pub_sock(s)
+
+  def send(self, s: str, dat: Union[bytes, capnp.lib.capnp._DynamicStructBuilder]) -> None:
+    if not isinstance(dat, bytes):
+      dat = dat.to_bytes()
+    self.sock[s].send(dat)
+
+  def wait_for_readers_to_update(self, s: str, timeout: int, dt: float = 0.05) -> bool:
+    for _ in range(int(timeout*(1./dt))):
+      if self.sock[s].all_readers_updated():
+        return True
+      time.sleep(dt)
+    return False
+
+  def all_readers_updated(self, s: str) -> bool:
+    return self.sock[s].all_readers_updated()  # type: ignore

cereal/messaging/tests/test_messaging.py

@@ -0,0 +1,185 @@
+import os
+import capnp
+import multiprocessing
+import numbers
+import random
+import threading
+import time
+from parameterized import parameterized
+import pytest
+
+from cereal import log, car
+import cereal.messaging as messaging
+from cereal.services import SERVICE_LIST
+
+events = [evt for evt in log.Event.schema.union_fields if evt in SERVICE_LIST.keys()]
+
+def random_sock():
+  return random.choice(events)
+
+def random_socks(num_socks=10):
+  return list({random_sock() for _ in range(num_socks)})
+
+def random_bytes(length=1000):
+  return bytes([random.randrange(0xFF) for _ in range(length)])
+
+def zmq_sleep(t=1):
+  if "ZMQ" in os.environ:
+    time.sleep(t)
+
+
+# TODO: this should take any capnp struct and returrn a msg with random populated data
+def random_carstate():
+  fields = ["vEgo", "aEgo", "brake", "steeringAngleDeg"]
+  msg = messaging.new_message("carState")
+  cs = msg.carState
+  for f in fields:
+    setattr(cs, f, random.random() * 10)
+  return msg
+
+# TODO: this should compare any capnp structs
+def assert_carstate(cs1, cs2):
+  for f in car.CarState.schema.non_union_fields:
+    # TODO: check all types
+    val1, val2 = getattr(cs1, f), getattr(cs2, f)
+    if isinstance(val1, numbers.Number):
+      assert val1 == val2, f"{f}: sent '{val1}' vs recvd '{val2}'"
+
+def delayed_send(delay, sock, dat):
+  def send_func():
+    sock.send(dat)
+  threading.Timer(delay, send_func).start()
+
+
+class TestMessaging:
+  def setUp(self):
+    # TODO: ZMQ tests are too slow; all sleeps will need to be
+    # replaced with logic to block on the necessary condition
+    if "ZMQ" in os.environ:
+      pytest.skip()
+
+    # ZMQ pub socket takes too long to die
+    # sleep to prevent multiple publishers error between tests
+    zmq_sleep()
+
+  @parameterized.expand(events)
+  def test_new_message(self, evt):
+    try:
+      msg = messaging.new_message(evt)
+    except capnp.lib.capnp.KjException:
+      msg = messaging.new_message(evt, random.randrange(200))
+    assert (time.monotonic() - msg.logMonoTime) < 0.1
+    assert not msg.valid
+    assert evt == msg.which()
+
+  @parameterized.expand(events)
+  def test_pub_sock(self, evt):
+    messaging.pub_sock(evt)
+
+  @parameterized.expand(events)
+  def test_sub_sock(self, evt):
+    messaging.sub_sock(evt)
+
+  @parameterized.expand([
+    (messaging.drain_sock, capnp._DynamicStructReader),
+    (messaging.drain_sock_raw, bytes),
+  ])
+  def test_drain_sock(self, func, expected_type):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sub_sock = messaging.sub_sock(sock, timeout=1000)
+    zmq_sleep()
+
+    # no wait and no msgs in queue
+    msgs = func(sub_sock)
+    assert isinstance(msgs, list)
+    assert len(msgs) == 0
+
+    # no wait but msgs are queued up
+    num_msgs = random.randrange(3, 10)
+    for _ in range(num_msgs):
+      pub_sock.send(messaging.new_message(sock).to_bytes())
+    time.sleep(0.1)
+    msgs = func(sub_sock)
+    assert isinstance(msgs, list)
+    assert all(isinstance(msg, expected_type) for msg in msgs)
+    assert len(msgs) == num_msgs
+
+  def test_recv_sock(self):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sub_sock = messaging.sub_sock(sock, timeout=100)
+    zmq_sleep()
+
+    # no wait and no msg in queue, socket should timeout
+    recvd = messaging.recv_sock(sub_sock)
+    assert recvd is None
+
+    # no wait and one msg in queue
+    msg = random_carstate()
+    pub_sock.send(msg.to_bytes())
+    time.sleep(0.01)
+    recvd = messaging.recv_sock(sub_sock)
+    assert isinstance(recvd, capnp._DynamicStructReader)
+    # https://github.com/python/mypy/issues/13038
+    assert_carstate(msg.carState, recvd.carState)
+
+  def test_recv_one(self):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sub_sock = messaging.sub_sock(sock, timeout=1000)
+    zmq_sleep()
+
+    # no msg in queue, socket should timeout
+    recvd = messaging.recv_one(sub_sock)
+    assert recvd is None
+
+    # one msg in queue
+    msg = random_carstate()
+    pub_sock.send(msg.to_bytes())
+    recvd = messaging.recv_one(sub_sock)
+    assert isinstance(recvd, capnp._DynamicStructReader)
+    assert_carstate(msg.carState, recvd.carState)
+
+  @pytest.mark.xfail(condition="ZMQ" in os.environ, reason='ZMQ detected')
+  def test_recv_one_or_none(self):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sub_sock = messaging.sub_sock(sock)
+    zmq_sleep()
+
+    # no msg in queue, socket shouldn't block
+    recvd = messaging.recv_one_or_none(sub_sock)
+    assert recvd is None
+
+    # one msg in queue
+    msg = random_carstate()
+    pub_sock.send(msg.to_bytes())
+    recvd = messaging.recv_one_or_none(sub_sock)
+    assert isinstance(recvd, capnp._DynamicStructReader)
+    assert_carstate(msg.carState, recvd.carState)
+
+  def test_recv_one_retry(self):
+    sock = "carState"
+    sock_timeout = 0.1
+    pub_sock = messaging.pub_sock(sock)
+    sub_sock = messaging.sub_sock(sock, timeout=round(sock_timeout*1000))
+    zmq_sleep()
+
+    # this test doesn't work with ZMQ since multiprocessing interrupts it
+    if "ZMQ" not in os.environ:
+      # wait 5 socket timeouts and make sure it's still retrying
+      p = multiprocessing.Process(target=messaging.recv_one_retry, args=(sub_sock,))
+      p.start()
+      time.sleep(sock_timeout*5)
+      assert p.is_alive()
+      p.terminate()
+
+    # wait 5 socket timeouts before sending
+    msg = random_carstate()
+    start_time = time.monotonic()
+    delayed_send(sock_timeout*5, pub_sock, msg.to_bytes())
+    recvd = messaging.recv_one_retry(sub_sock)
+    assert (time.monotonic() - start_time) >= sock_timeout*5
+    assert isinstance(recvd, capnp._DynamicStructReader)
+    assert_carstate(msg.carState, recvd.carState)

cereal/messaging/tests/test_pub_sub_master.py

@@ -0,0 +1,160 @@
+import random
+import time
+from typing import Sized, cast
+
+import cereal.messaging as messaging
+from cereal.messaging.tests.test_messaging import events, random_sock, random_socks, \
+                                                  random_bytes, random_carstate, assert_carstate, \
+                                                  zmq_sleep
+from cereal.services import SERVICE_LIST
+
+
+class TestSubMaster:
+
+  def setup_method(self):
+    # ZMQ pub socket takes too long to die
+    # sleep to prevent multiple publishers error between tests
+    zmq_sleep(3)
+
+  def test_init(self):
+    sm = messaging.SubMaster(events)
+    for p in [sm.updated, sm.recv_time, sm.recv_frame, sm.alive,
+              sm.sock, sm.data, sm.logMonoTime, sm.valid]:
+      assert len(cast(Sized, p)) == len(events)
+
+  def test_init_state(self):
+    socks = random_socks()
+    sm = messaging.SubMaster(socks)
+    assert sm.frame == -1
+    assert not any(sm.updated.values())
+    assert not any(sm.seen.values())
+    on_demand = {s: SERVICE_LIST[s].frequency <= 1e-5 for s in sm.services}
+    assert all(sm.alive[s] == sm.valid[s] == sm.freq_ok[s] == on_demand[s] for s in sm.services)
+    assert all(t == 0. for t in sm.recv_time.values())
+    assert all(f == 0 for f in sm.recv_frame.values())
+    assert all(t == 0 for t in sm.logMonoTime.values())
+
+    for p in [sm.updated, sm.recv_time, sm.recv_frame, sm.alive,
+              sm.sock, sm.data, sm.logMonoTime, sm.valid]:
+      assert len(cast(Sized, p)) == len(socks)
+
+  def test_getitem(self):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sm = messaging.SubMaster([sock,])
+    zmq_sleep()
+
+    msg = random_carstate()
+    pub_sock.send(msg.to_bytes())
+    sm.update(1000)
+    assert_carstate(msg.carState, sm[sock])
+
+  # TODO: break this test up to individually test SubMaster.update and SubMaster.update_msgs
+  def test_update(self):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sm = messaging.SubMaster([sock,])
+    zmq_sleep()
+
+    for i in range(10):
+      msg = messaging.new_message(sock)
+      pub_sock.send(msg.to_bytes())
+      sm.update(1000)
+      assert sm.frame == i
+      assert all(sm.updated.values())
+
+  def test_update_timeout(self):
+    sock = random_sock()
+    sm = messaging.SubMaster([sock,])
+    timeout = random.randrange(1000, 3000)
+    start_time = time.monotonic()
+    sm.update(timeout)
+    t = time.monotonic() - start_time
+    assert t >= timeout/1000.
+    assert t < 3
+    assert not any(sm.updated.values())
+
+  def test_avg_frequency_checks(self):
+    for poll in (True, False):
+      sm = messaging.SubMaster(["modelV2", "carParams", "carState", "cameraOdometry", "liveCalibration"],
+                               poll=("modelV2" if poll else None),
+                               frequency=(20. if not poll else None))
+
+      checks = {
+        "carState": (20, 20),
+        "modelV2": (20, 20 if poll else 10),
+        "cameraOdometry": (20, 10),
+        "liveCalibration": (4, 4),
+        "carParams": (None, None),
+        "userBookmark": (None, None),
+      }
+
+      for service, (max_freq, min_freq) in checks.items():
+        if max_freq is not None:
+          assert sm._check_avg_freq(service)
+          assert sm.freq_tracker[service].max_freq == max_freq*1.2
+          assert sm.freq_tracker[service].min_freq == min_freq*0.8
+        else:
+          assert not sm._check_avg_freq(service)
+
+  def test_alive(self):
+    pass
+
+  def test_ignore_alive(self):
+    pass
+
+  def test_valid(self):
+    pass
+
+  # SubMaster should always conflate
+  def test_conflate(self):
+    sock = "carState"
+    pub_sock = messaging.pub_sock(sock)
+    sm = messaging.SubMaster([sock,])
+
+    n = 10
+    for i in range(n+1):
+      msg = messaging.new_message(sock)
+      msg.carState.vEgo = i
+      pub_sock.send(msg.to_bytes())
+      time.sleep(0.01)
+    sm.update(1000)
+    assert sm[sock].vEgo == n
+
+
+class TestPubMaster:
+
+  def setup_method(self):
+    # ZMQ pub socket takes too long to die
+    # sleep to prevent multiple publishers error between tests
+    zmq_sleep(3)
+
+  def test_init(self):
+    messaging.PubMaster(events)
+
+  def test_send(self):
+    socks = random_socks()
+    pm = messaging.PubMaster(socks)
+    sub_socks = {s: messaging.sub_sock(s, conflate=True, timeout=1000) for s in socks}
+    zmq_sleep()
+
+    # PubMaster accepts either a capnp msg builder or bytes
+    for capnp in [True, False]:
+      for i in range(100):
+        sock = socks[i % len(socks)]
+
+        if capnp:
+          try:
+            msg = messaging.new_message(sock)
+          except Exception:
+            msg = messaging.new_message(sock, random.randrange(50))
+        else:
+          msg = random_bytes()
+
+        pm.send(sock, msg)
+        recvd = sub_socks[sock].receive()
+
+        if capnp:
+          msg.clear_write_flag()
+          msg = msg.to_bytes()
+        assert msg == recvd, i

cereal/messaging/tests/test_services.py

@@ -0,0 +1,27 @@
+import os
+import tempfile
+from typing import Dict
+from parameterized import parameterized
+
+from cereal import log
+import cereal.services as services
+from cereal.services import SERVICE_LIST
+
+
+class TestServices:
+
+  @parameterized.expand(SERVICE_LIST.keys())
+  def test_services(self, s):
+    service = SERVICE_LIST[s]
+    assert service.frequency <= 104
+    assert service.decimation != 0
+
+  def test_generated_header(self):
+    with tempfile.NamedTemporaryFile(suffix=".h") as f:
+      ret = os.system(f"python3 {services.__file__} > {f.name} && clang++ {f.name} -std=c++11")
+      assert ret == 0, "generated services header is not valid C"
+
+  def test_all_services_exist_in_log_union(self):
+    event_fields = set(log.Event.schema.union_fields)
+    missing = sorted(s for s in SERVICE_LIST if s not in event_fields)
+    assert not missing, f"services missing from log.capnp Event union: {missing}"

cereal/messaging/tests/validate_sp_cereal_upstream.py

@@ -0,0 +1,222 @@
+#!/usr/bin/env python3
+import argparse
+import sys
+from typing import Any, List, Tuple
+
+DEBUG = False
+
+
+def print_debug(string: str) -> None:
+  if DEBUG:
+    print(string)
+
+
+def create_schema_instance(struct: Any, prop: Tuple[str, Any]) -> Any:
+  """
+  Create a new instance of a schema type, handling different field types.
+
+  Args:
+      struct: The Cap'n Proto schema structure
+      prop: A tuple containing the field name and field metadata
+
+  Returns:
+      A new initialized schema instance
+  """
+  struct_instance = struct.new_message()
+  field_name, field_metadata = prop
+
+  try:
+    field_type = field_metadata.proto.slot.type.which()
+
+    # Initialize different types of fields
+    if field_type in ('list', 'text', 'data'):
+      struct_instance.init(field_name, 1)
+      print_debug(f"Initialized list/text/data field: {field_name}")
+    elif field_type in ('struct', 'object'):
+      struct_instance.init(field_name)
+      print_debug(f"Initialized struct/object field: {field_name}")
+
+    return struct_instance
+
+  except Exception as e:
+    print(f"Error creating instance for {field_name}: {e}")
+    return None
+
+
+def get_schema_fields(schema_struct: Any) -> List[Tuple[str, Any]]:
+  """
+  Retrieve all fields from a given schema structure.
+
+  Args:
+      schema_struct: The Cap'n Proto schema structure
+
+  Returns:
+      A list of field names and their metadata
+  """
+  try:
+    # Get all fields from the schema
+    schema_fields = list(schema_struct.schema.fields.items())
+
+    print_debug("Discovered schema fields:")
+    for field_name, field_metadata in schema_fields:
+      print_debug(f"- {field_name}")
+
+    return schema_fields
+
+  except Exception as e:
+    print(f"Error retrieving schema fields: {e}")
+    return []
+
+
+def generate_schema_instances(schema_struct: Any) -> List[Any]:
+  """
+  Generate instances for all fields in a given schema.
+
+  Args:
+      schema_struct: The Cap'n Proto schema structure
+
+  Returns:
+      A list of schema instances
+  """
+  schema_fields = get_schema_fields(schema_struct)
+  instances = []
+
+  for field_prop in schema_fields:
+    try:
+      instance = create_schema_instance(schema_struct, field_prop)
+      if instance is not None:
+        instances.append(instance)
+    except Exception as e:
+      print(f"Skipping field due to error: {e}")
+
+  print(f"Generated {len(instances)} schema instances")
+  return instances
+
+
+def persist_instances(instances: List[Any], filename: str) -> None:
+  """
+  Write schema instances to a binary file.
+
+  Args:
+      instances: List of schema instances
+      filename: Output file path
+  """
+  try:
+    with open(filename, 'wb') as f:
+      for instance in instances:
+        f.write(instance.to_bytes())
+
+    print(f"Successfully wrote {len(instances)} instances to {filename}")
+
+  except Exception as e:
+    print(f"Error persisting instances: {e}")
+    sys.exit(1)
+
+
+def read_instances(filename: str, schema_type: Any) -> List[Any]:
+  """
+  Read schema instances from a binary file.
+
+  Args:
+      filename: Input file path
+      schema_type: The schema type to use for reading
+
+  Returns:
+      A list of read schema instances
+  """
+  try:
+    with open(filename, 'rb') as f:
+      data = f.read()
+
+    instances = list(schema_type.read_multiple_bytes(data))
+
+    print(f"Read {len(instances)} instances from {filename}")
+    return instances
+
+  except Exception as e:
+    print(f"Error reading instances: {e}")
+    sys.exit(1)
+
+
+def compare_schemas(original_instances: List[Any], read_instances: List[Any]) -> bool:
+  """
+  Compare original and read-back instances to detect potential breaking changes.
+
+  Args:
+      original_instances: List of originally generated instances
+      read_instances: List of instances read back from file
+
+  Returns:
+      Boolean indicating whether schemas appear compatible
+  """
+  if len(original_instances) != len(read_instances):
+    print("❌ Schema Compatibility Warning: Instance count mismatch")
+    return False
+
+  compatible = True
+  for struct in read_instances:
+    try:
+      getattr(struct, struct.which())  # Attempting to access the field to validate readability
+    except Exception as e:
+      print(f"❌ Structural change detected: {struct.which()} is not readable.\nFull error: {e}")
+      compatible = False
+
+  return compatible
+
+
+def main():
+  """
+  CLI entry point for schema compatibility testing.
+  """
+  # Setup argument parser
+  parser = argparse.ArgumentParser(
+    description='Cap\'n Proto Schema Compatibility Testing Tool',
+    epilog='Test schema compatibility by generating and reading back instances.'
+  )
+
+  # Add mutually exclusive group for generation or reading mode
+  mode_group = parser.add_mutually_exclusive_group(required=True)
+  mode_group.add_argument('-g', '--generate', action='store_true',
+                          help='Generate schema instances')
+  mode_group.add_argument('-r', '--read', action='store_true',
+                          help='Read and validate schema instances')
+
+  # Common arguments
+  parser.add_argument('-f', '--file',
+                      default='schema_instances.bin',
+                      help='Output/input binary file (default: schema_instances.bin)')
+
+  # Parse arguments
+  args = parser.parse_args()
+
+  # Import the schema dynamically 
+  try:
+    from cereal import log
+    schema_type = log.Event
+  except ImportError:
+    print("Error: Unable to import schema. Ensure 'cereal' is installed.")
+    sys.exit(1)
+
+  # Execute based on mode
+  if args.generate:
+    print("🔧 Generating Schema Instances")
+    instances = generate_schema_instances(schema_type)
+    persist_instances(instances, args.file)
+    print("✅ Instance generation complete")
+
+  elif args.read:
+    print("🔍 Reading and Validating Schema Instances")
+    generated_instances = generate_schema_instances(schema_type)
+    read_back_instances = read_instances(args.file, schema_type)
+
+    # Compare schemas
+    if compare_schemas(generated_instances, read_back_instances):
+      print("✅ Schema Compatibility: No breaking changes detected")
+      sys.exit(0)
+    else:
+      print("❌ Potential Schema Breaking Changes Detected")
+      sys.exit(1)
+
+
+if __name__ == "__main__":
+  main()