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Wait for port availability before aborting startup #2304

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47 changes: 40 additions & 7 deletions main.py
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Original file line number Diff line number Diff line change
Expand Up @@ -397,6 +397,32 @@ def get_port_usage(port: int) -> str:
return ""


def wait_for_port_to_become_available(
port: int, timeout: float = 15.0, interval: float = 0.5
) -> bool:
"""Wait for a TCP port to become available.

Args:
port: TCP port to check.
timeout: Maximum seconds to wait for the port to free.
interval: Seconds to sleep between checks.

Returns:
bool: ``True`` if the port became available within the timeout.
Comment on lines +407 to +411
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Copilot AI Nov 14, 2025

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[nitpick] The docstring says "Maximum seconds to wait for the port to free" but this doesn't account for the early return when IN_DOCKER is set. Consider clarifying the documentation:

"""Wait for a TCP port to become available.

Args:
    port: TCP port to check.
    timeout: Maximum seconds to wait for the port to free (ignored in Docker).
    interval: Seconds to sleep between checks.

Returns:
    bool: ``True`` if the port became available within the timeout,
          or if running in Docker. ``False`` if the timeout was reached.
"""
Suggested change
timeout: Maximum seconds to wait for the port to free.
interval: Seconds to sleep between checks.
Returns:
bool: ``True`` if the port became available within the timeout.
timeout: Maximum seconds to wait for the port to free (ignored if running in Docker).
interval: Seconds to sleep between checks.
Returns:
bool: ``True`` if the port became available within the timeout,
or if running in Docker. ``False`` if the timeout was reached.

Copilot uses AI. Check for mistakes.
"""

if os.environ.get("IN_DOCKER"):
return True

deadline = time.monotonic() + timeout
while time.monotonic() < deadline:
if not is_port_in_use(port):
return True
time.sleep(interval)

return not is_port_in_use(port)


def main(argv=None):
"""Entry point for the ``glimpser`` command."""
# Clear the console before starting
Expand All @@ -415,19 +441,26 @@ def main(argv=None):
display_startup_info(args)

if is_port_in_use(config.PORT) and config.DEBUG_MODE is False:
logging.error(
"Error: Port %s is already in use. Please choose a different port.",
logging.warning(
"Port %s is already in use. Waiting for it to become available...",
config.PORT,
)
usage = get_port_usage(config.PORT)
if usage:
logging.error("Processes using port %s:\n%s", config.PORT, usage)
if wait_for_port_to_become_available(config.PORT):
logging.info("Port %s became available. Continuing startup.", config.PORT)
else:
logging.error(
"Could not determine which process is using port %s.",
"Error: Port %s is already in use. Please choose a different port.",
config.PORT,
)
sys.exit(1)
usage = get_port_usage(config.PORT)
if usage:
logging.error("Processes using port %s:\n%s", config.PORT, usage)
else:
logging.error(
"Could not determine which process is using port %s.",
config.PORT,
)
sys.exit(1)

try:
logging.info(
Expand Down
30 changes: 30 additions & 0 deletions tests/test_main_utilities.py
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Original file line number Diff line number Diff line change
Expand Up @@ -170,6 +170,36 @@ def test_get_port_usage_fuser_fallback(self, mock_run):
self.assertEqual(mock_run.call_args_list, expected_calls)
self.assertEqual(output, "fuser output")

@patch("main.time.sleep")
@patch("main.time.monotonic")
@patch("main.is_port_in_use")
def test_wait_for_port_to_become_available_success(
self, mock_in_use, mock_monotonic, mock_sleep
):
mock_monotonic.side_effect = [0.0, 0.0, 0.6]
mock_in_use.side_effect = [True, False]

result = main.wait_for_port_to_become_available(8082, timeout=1.0, interval=0.5)

self.assertTrue(result)
self.assertEqual(mock_in_use.call_count, 2)
self.assertEqual(mock_sleep.call_args_list, [call(0.5)])

@patch("main.time.sleep")
@patch("main.time.monotonic")
@patch("main.is_port_in_use")
def test_wait_for_port_to_become_available_timeout(
self, mock_in_use, mock_monotonic, mock_sleep
):
mock_monotonic.side_effect = [0.0, 0.0, 0.6, 1.2]
mock_in_use.side_effect = [True, True, True]

result = main.wait_for_port_to_become_available(8082, timeout=1.0, interval=0.5)

self.assertFalse(result)
self.assertEqual(mock_in_use.call_count, 3)
self.assertEqual(mock_sleep.call_args_list, [call(0.5), call(0.5)])


if __name__ == "__main__":
unittest.main()
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