Can only call write_image a certain number of times before process hangs

[slishak]

Using Orca to export multiple static PDF files, when I get to the 25th file the process hangs and never completes. The limiting number of files seems to depend on the file type:
pdf, svg: 24 files written
png, jpg, webp: 25 files written before hanging

The same happens whether I write to a file or a BytesIO stream. For interest, the reason I'm doing this is to write a multi-page PDF as per the issue here plotly/orca#143.

import plotly.io as pio
import plotly.graph_objs as go
import io
import numpy as np


def make_figure():
    """Function to make random figure"""
    x = np.linspace(0, 10, 100)
    y = np.random.randint(1, 100, 100)

    trace = go.Scatter(x=x, y=y, mode='markers')
    return go.Figure(data=[trace])


use_stream = False
filetype = 'pdf'

for i in range(50):
    print('Page {}'.format(i+1))

    if use_stream:
        pdf_file = io.BytesIO()
    else:
        pdf_file = '{}.{}'.format(i, filetype)

    pio.write_image(make_figure(), pdf_file, filetype)

I can circumvent the issue by adding the following line into the loop to periodically restart the Orca server:

    if (i+1) % 20 == 0:
        pio._orca.shutdown_server()

Versions:

Windows 7 Professional
Python 3.6.4 x64

plotly==3.3.0
psutil==5.4.8

Node.js v8.12.0
npm@6.4.1
electron@1.8.4
orca@1.1.1

[jonmmease]

Hi @slishak, thanks very much for the detailed report. I will try to reproduce on a windows vm (although I only have access to windows 10). Out of curiosity, have you tried installing orca with conda or the windows installer? I don’t know that these would behave differently, but these version of orca have gone through the electron packing process.

[slishak]

Neither - I installed using npm and pip as per https://plot.ly/python/static-image-export/#npm--pip

[jonmmease]

I was able to reproduce this on my windows 10 VM and the number of exports at which the process hangs exactly matches your report. This does not hang on OS X or Linux even out to 1000 images 🤔

Next I'll try to reproduce without plotly.py

[jonmmease]

Closed by #1262. Could you give the 3.4.1 release candidate a try and confirm that it fixes the issue for you? Installation instructions for the release candidate at https://github.com/plotly/plotly.py/tree/release_3.4.1

Thanks again for taking the time to to report this!

[slishak]

That appears to have done the trick, just wrote a 200 page PDF without having to restart Orca! Thanks for looking into it.

[jonmmease]

Great! Thanks for giving the release candidate a try.