fix: KALEIDO_RENDER_TIMEOUT

[bitmaybewise]

I managed to reproduce this issue #419 locally using this script:

"""Repro for plotly/Kaleido issue #419 (write_image hangs with many points)."""

import argparse
import time

import numpy as np
import plotly.graph_objects as go


def build_traces(num_points: int, lines: int, dtype: str):
    if lines < 1:
        raise ValueError("lines must be >= 1")

    points_per_line = num_points // lines
    remainder = num_points % lines
    numpy_dtype = np.float64 if dtype == "float" else np.int64
    traces = []

    for i in range(lines):
        count = points_per_line + (1 if i < remainder else 0)
        x = np.full(count, 1, dtype=numpy_dtype)
        y = np.full(count, 0.5, dtype=numpy_dtype)
        traces.append(go.Scatter(x=x, y=y))

    return traces


def main():
    parser = argparse.ArgumentParser(
        description="Reproduce Kaleido write_image hang with many datapoints."
    )
    parser.add_argument(
        "--points",
        type=int,
        default=4_914_834,
        help="Total number of datapoints (default matches issue #419).",
    )
    parser.add_argument(
        "--lines",
        type=int,
        default=1,
        help="Number of Scatter traces to split points across.",
    )
    parser.add_argument(
        "--dtype",
        choices=("float", "int"),
        default="float",
        help="Array dtype for x/y values.",
    )
    parser.add_argument(
        "--output",
        default="output.png",
        help="Output image path.",
    )
    args = parser.parse_args()

    traces = build_traces(args.points, args.lines, args.dtype)
    fig = go.Figure(data=traces)

    print(
        f"Writing image with {args.points} points across {args.lines} trace(s) "
        f"using {args.dtype} arrays..."
    )
    start = time.perf_counter()
    fig.write_image(args.output)
    elapsed = time.perf_counter() - start
    print(f"Done in {elapsed:.2f}s -> {args.output}")


if __name__ == "__main__":
    main()

This hangs:

uv run integration_tests/repro_issue_419.py
Writing image with 4914834 points across 1 trace(s) using float arrays...

Although I don't know how to fix the underlying issue making the process to hang, I think it's a sane to be able to define a timeout threshold, which is what I introduced in this pull request.

With the timeout:

KALEIDO_RENDER_TIMEOUT=10 uv run --project src/py integration_tests/repro_issue_419.py
Writing image with 4914834 points across 1 trace(s) using float arrays...
Traceback (most recent call last):
  File "integration_tests/repro_issue_419.py", line 71, in <module>
    main()
  File "integration_tests/repro_issue_419.py", line 65, in main
    fig.write_image(args.output)
  File "/Users/hercules/BitMaybeWise/github/Kaleido/src/py/.venv/lib/python3.8/site-packages/plotly/basedatatypes.py", line 3895, in write_image
    return pio.write_image(self, *args, **kwargs)
  File "/Users/hercules/BitMaybeWise/github/Kaleido/src/py/.venv/lib/python3.8/site-packages/plotly/io/_kaleido.py", line 510, in write_image
Wait expired, Browser is being closed by watchdog.
    img_data = to_image(
  File "/Users/hercules/BitMaybeWise/github/Kaleido/src/py/.venv/lib/python3.8/site-packages/plotly/io/_kaleido.py", line 380, in to_image
    img_bytes = kaleido.calc_fig_sync(
  File "/Users/hercules/BitMaybeWise/github/Kaleido/src/py/kaleido/__init__.py", line 191, in calc_fig_sync
    return _sync_server.oneshot_async_run(
  File "/Users/hercules/BitMaybeWise/github/Kaleido/src/py/kaleido/_sync_server.py", line 243, in oneshot_async_run
    raise TimeoutError(
TimeoutError: Kaleido sync call exceeded the timeout; Chrome termination attempted.