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Refactor subprocess mixin to control setting up and tearing down chil… (
#894) The Subprocess mixin can be used to control setting up and tearing down child process. The `TestServerBase` will leverage this and it will be re-used by a xDS configuration generator. Signed-off-by: Kevin Baichoo <kbaichoo@google.com>
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,81 @@ | ||
| """Mixin for managing child subprocess with an additional thread.""" | ||
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| from threading import Thread, Condition | ||
| import subprocess | ||
| import logging | ||
| from abc import ABC, abstractmethod | ||
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| class SubprocessMixin(ABC): | ||
| """Mixin used to manage launching subprocess using a separate Python thread. | ||
| See test_subprocess_captures_stdout and test_subprocess_stop to see usage | ||
| of the mixin. | ||
| """ | ||
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| def __init__(self): | ||
| """Create SubprocessMixin.""" | ||
| self._server_thread = Thread(target=self._serverThreadRunner) | ||
| self._server_process = None | ||
| self._has_launched = False | ||
| self._has_launched_cv = Condition() | ||
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| @abstractmethod | ||
| def _argsForSubprocess(self) -> list[str]: | ||
| """Return the args to launch the subprocess.""" | ||
| pass | ||
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| def _serverThreadRunner(self): | ||
| """Routine executed by the python thread that launches the child subprocess. | ||
| Derived classes may wish to extend this to use the stdout, stderr of | ||
| the child process. | ||
| """ | ||
| args = self._argsForSubprocess() | ||
| logging.info("Test server popen() args: %s" % str.join(" ", args)) | ||
| self._server_process = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE) | ||
| with self._has_launched_cv: | ||
| self._has_launched = True | ||
| self._has_launched_cv.notify_all() | ||
| stdout, stderr = self._server_process.communicate() | ||
| logging.info("Process stdout: %s", stdout.decode("utf-8")) | ||
| logging.info("Process stderr: %s", stderr.decode("utf-8")) | ||
| return stdout, stderr | ||
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| def launchSubprocess(self): | ||
| """Start the subprocess.""" | ||
| self._server_thread.daemon = True | ||
| self._server_thread.start() | ||
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| def waitUntilSubprocessLaunched(self): | ||
| """Blocks until the subprocess has launched at least once.""" | ||
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| def hasLaunched(): | ||
| return self._has_launched | ||
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| with self._has_launched_cv: | ||
| self._has_launched_cv.wait_for(hasLaunched) | ||
| assert self._has_launched | ||
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| def waitForSubprocessNotRunning(self): | ||
| """Wait for the subprocess to not be running assuming it exits.""" | ||
| if not self._has_launched or not self._server_thread.is_alive(): | ||
| return | ||
| self._server_thread.join() | ||
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| def hasLaunched(): | ||
| return self._has_launched | ||
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| with self._has_launched_cv: | ||
| self._has_launched_cv.wait_for(hasLaunched) | ||
| assert self._has_launched | ||
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| def stopSubprocess(self) -> int: | ||
| """Stop the subprocess. | ||
| Returns: | ||
| Int: exit code of the server process. | ||
| """ | ||
| self._server_process.terminate() | ||
| self._server_thread.join() | ||
| return self._server_process.returncode |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,54 @@ | ||
| """Contains unit tests for subprocess_mixin.py.""" | ||
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| import pytest | ||
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| from test.integration.subprocess_mixin import SubprocessMixin | ||
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| class TestSubprocessMixin(SubprocessMixin): | ||
| """Helper class for testing the SubprocessMixin.""" | ||
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| def __init__(self, args): | ||
| """Create the TestSubprocessMixin.""" | ||
| super().__init__() | ||
| self.args = args | ||
| self.stdout = b'' | ||
| self.stderr = b'' | ||
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| def _argsForSubprocess(self) -> list[str]: | ||
| return self.args | ||
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| def _serverThreadRunner(self): | ||
| self.stdout, self.stderr = super()._serverThreadRunner() | ||
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| def test_subprocess_captures_stdout(): | ||
| """Test the subprocess captures stdout.""" | ||
| child_process = TestSubprocessMixin(['echo', 'stdout']) | ||
| child_process.launchSubprocess() | ||
| child_process.waitUntilSubprocessLaunched() | ||
| child_process.waitForSubprocessNotRunning() | ||
| assert b'stdout' in child_process.stdout | ||
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| def test_subprocess_captures_stderr(): | ||
| """Test the subprocess captures stderr.""" | ||
| child_process = TestSubprocessMixin(['logger', '--no-act', '-s', 'stderr']) | ||
| child_process.launchSubprocess() | ||
| child_process.waitUntilSubprocessLaunched() | ||
| child_process.waitForSubprocessNotRunning() | ||
| assert child_process.stderr != b'' | ||
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| def test_subprocess_stop(): | ||
| """Test the subprocess can be stopped.""" | ||
| child_process = TestSubprocessMixin(['sleep', '120']) | ||
| child_process.launchSubprocess() | ||
| child_process.waitUntilSubprocessLaunched() | ||
| ret_code = child_process.stopSubprocess() | ||
| # Non-zero exit is expected as the subprocess should be killed. | ||
| assert ret_code != 0 | ||
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| if __name__ == '__main__': | ||
| raise SystemExit(pytest.main([__file__, '--assert=plain'])) |