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Flush output in Python before running execvp #2258

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Merged
merged 1 commit into from
Mar 21, 2025
Merged

Flush output in Python before running execvp #2258

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5 changes: 3 additions & 2 deletions images/base-notebook/start-notebook.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,8 @@
# If we are in a JupyterHub, we pass on to `start-singleuser.py` instead so it does the right thing
if "JUPYTERHUB_API_TOKEN" in os.environ:
print(
"WARNING: using start-singleuser.py instead of start-notebook.py to start a server associated with JupyterHub."
"WARNING: using start-singleuser.py instead of start-notebook.py to start a server associated with JupyterHub.",
flush=True,
)
command = ["/usr/local/bin/start-singleuser.py"] + sys.argv[1:]
os.execvp(command[0], command)
Expand Down Expand Up @@ -40,5 +41,5 @@
command += sys.argv[1:]

# Execute the command!
print("Executing: " + " ".join(command))
print("Executing: " + " ".join(command), flush=True)
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@mathbunnyru mathbunnyru Mar 21, 2025 •
edited
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I think what was going on without TTY is that the output was buffered and this buffer was lost and not flushed, so the test was failing.

Adding flush allows us to write a test without a tty (the lost output is required in the test)

os.execvp(command[0], command)
2 changes: 1 addition & 1 deletion images/base-notebook/start-singleuser.py
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Expand Up @@ -20,5 +20,5 @@
command += sys.argv[1:]

# Execute the command!
print("Executing: " + " ".join(command))
print("Executing: " + " ".join(command), flush=True)
os.execvp(command[0], command)
6 changes: 1 addition & 5 deletions tests/by_image/base-notebook/test_start_container.py
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Expand Up @@ -42,11 +42,7 @@ def test_start_notebook(
f"Test that the start-notebook.py launches the {expected_command} server from the env {env} ..."
)
host_port = find_free_port()
container.run_detached(
tty=True,
environment=env,
ports={"8888/tcp": host_port},
)
container.run_detached(environment=env, ports={"8888/tcp": host_port})
# sleeping some time to let the server start
time.sleep(2)
logs = container.get_logs()
Expand Down