Cannot load `*.so` libraries in a directory specified by AppSetting(Environment variables) `LD_LIBRARY_PATH`.

I want to load so libraries for python package opencv-python-headless.

Investigative information

• Timestamp: 2019-10-06 03:48:02 (UTC)
• InvocationId: 58ab63f9-096e-423a-be88-ef1870d98a79
• Function App name: pythonfunc1
• Function name(s) (as appropriate): HttpTrigger
• Core Tools version: 2.7.1633

Repro steps

1. Deploy function app package including some so files.
   The file structure is following.

$ tree .
.
├── host.json
├── HttpTrigger
│   ├── function.json
│   ├── __init__.py
│   └── sample.dat
├── local.settings.json
├── proxies.json
├── requirements.txt
└── tmp
    ├── libglib-2.0.so.0
    └── libgthread-2.0.so.0

1. Set App Setting LD_LIBRARY_PATH to /home/site/wwwroot/tmp in order to load above so files.

2. Execute the function.

Expected behavior

import cv2 in __init__.py will work without any error/exception

Actual behavior

Following exception occurred, of cause http response code is 500.

Result: Failure
Exception: ImportError: libgthread-2.0.so.0: cannot open shared object file: No such file or directory

I confirmed that /home/site/wwwroot/tmp was set to enviroment variable LD_LIBRARY_PATH by using os.getenv('LD_LIBRARY_PATH') in my function program. I’m not sure why *.so libraries in a path specified by LD_LIBRARY_PATH cannot be loaded even though the path can be set appropriately in the environment variable LD_LIBRARY_PATH.

Known workarounds

The function with following code instead of import cv2

import ctypes
import importlib

exlibpath = os.path.dirname(os.path.dirname(os.path.abspath(__file__))) + '/tmp/'
ctypes.CDLL(exlibpath + 'libglib-2.0.so.0')
ctypes.CDLL(exlibpath + 'libgthread-2.0.so.0')

cv2 = importlib.import_module('cv2')

Related information

• Links to source
• Contents of the requirements.txt file
• Bindings used

Source

Function code:

# __init__.py

import logging
import os
import urllib.request as rq
import re
import azure.functions as func
import mimetypes

import cv2

# work around code
# import ctypes
# import importlib

# exlibpath = os.path.dirname(os.path.dirname(os.path.abspath(__file__))) + '/tmp/'
# ctypes.CDLL(exlibpath + 'libglib-2.0.so.0')
# ctypes.CDLL(exlibpath + 'libgthread-2.0.so.0')

# cv2 = importlib.import_module('cv2')

def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')

    image_url = req.params.get('image_url')
    if not image_url:
        try:
            req_body = req.get_json()
        except ValueError:
            pass
        else:
            image_url = req_body.get('image_url')

    if image_url:
        local = re.sub(r'^.*/([^/]+)$', r'\1', image_url)
        rq.urlretrieve(image_url, '/tmp/' + local)
        im = cv2.imread('/tmp/' + local)
        gry = cv2.cvtColor(im, cv2.COLOR_BGR2GRAY)
        cv2.imwrite('/tmp/gray_' + local, gry)
        with open('/tmp/gray_' + local, 'rb') as f:
            mimetype = mimetypes.guess_type('/tmp/gray_' + local)
            return func.HttpResponse(f.read(), mimetype=mimetype[0])
        # return func.HttpResponse(f"Hello {image_url}!")
    else:
        return func.HttpResponse(
             "Please pass a image_url on the query string or in the request body",
             status_code=400
        )

requirements.txt:

opencv-python-headless

[mlazowik]

Python uses ld to find libraries in LD_LIBRARY_PATH, but ld is not present in the runtime. https://hg.python.org/cpython/rev/385181e809bc#l3.10

[anirudhgarg]

@horihiro @mlazowik we have added the binutils to the python images and also added the .so libraries needed for OpenCV. Not sure at this point how we can fix this issue of loading any *.so so closing this out.