Python Grpc client service method does not return when called from httpd on Oracle Linux

[Manosh Padannayil]

Hello All,

   I am getting the exact same issue reported in the below thread but for Oracle Linux OS.

https://github.com/grpc/grpc/issues/13050

Issue: Python Grpc client service method does not return when called from httpd on Oracle Linux. It works from eclipse in OSX. Works from python terminal in Oracle Linux, fails only when it is called from within httpd in Oracle Linux.

Configuration

Oracle Linux 7.8

httpd-2.4.41, 2.4.46

Python 3.8.0, 3.9.0

  Django 2.2.6

  grpcio 1.32.0

  grpcio-tools 1.32.0

  mod-wsgi 4.7.1

  mod-wsgi-httpd 2.4.41.1

Pseudo code:

from my.service import my_service_pb2_grpc

with open('/path/to/pem/file', 'rb') as f:

  trusted_certs = f.read()

with open('path/to/key/file', 'rb') as f:

  cert_key = f.read()

cred = grpc.ssl_channel_credentials(root_certificate=trusted_certs, private_key=cert_key, certificate_chain=trusted_certs)

channel = grpc.secure_channel('{}:{}'.format('server_url',443), cred)

stub = my_service_pb2_grpc.MyServiceStub(channel)

response = stub.MyMethod(MyRequest)

I tried with options grpc.keepalive_timeout_ms and   grpc.keepalive_time as 10000, but no luck.

Could anyone please help me on this?

Thanks and Regards,

Manosh Padannayil

[Graham Dumpleton]

Are you forcing the use of the main Python interpreter?

https://modwsgi.readthedocs.io/en/master/user-guides/application-issues.html#python-simplified-gil-state-api

Likely their Python wrapper module isn't designed to work in Python sub interpreters.

Also, are you using system Apache or mod_wsgi-express? Your configuration list is confusing since you mention multiple Apache versions as well as pip installed mod_wsgi and mod_wsgi-httpd packages.

If you are using system Apache, you should not have mod_wsgi-httpd package installed and doing so could screw things up if trying to use mod_wsgi install against it with system Apache.

Finally, are you using system Python packages, or Python from Python Software Foundation. You cannot use Anaconda Python if you want to be able to use SSL in Apache and Python.

Graham

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[Manosh Padannayil]

Hi Graham,

    Thanks for the reply. I tried different options as mentioned in the reply. Tried different versions of Python and http, but no luck.

Actually, I compiled, httpd and python source code and installed the python package mod_wsgi. 

Below are the detailed steps I did;

In a fresh VM: Oracle Linux 7.8

1.  yum upgrade

yum update

yun install openssl-devel

yun install libffi-devel

2. Compiled the following latest packages with prefix as  --prefix=/path/to/apache/home

pcre2-10.35

expat-2.2.10

apr-1.6.5

apr-util-1.6.1

httpd-4.4.46 : compiled with --enable-ssl --enable-so

3. Compiled python-3.9.0 with prefix as --prefix=/path/to/python/install/home

4. Install python packages: all latest versions:

python3 -m pip install grpcio grpcio-tools protobuf mod-wsgi DJango

4. Configured /path/to/apache/home/conf/httpd.conf as below

    

    Listen 9000

    User my_username

    Group my_group

    ServerName localhost:9000

<Directory "/">

Require all granted

</Directory>

WSGIPythonHome /path/to/python/install/home

LoadModule wsgi_module /path/to/python/install/home/lib/python3.9/site-packages/mod_wsgi/server/mod_wsgi-py39-cpython-39-x86_64-linux-gnu.so

Started the apache as /path/to/apache/home/bin/apachectl start

Below are the logs obtained.

If I understood correctly from last reply, the python subinterpreter is loaded instead of primary interpreter when a GRPC api is invoked, causing the deadlock.

Please let me know how to get rid of this deadlock issue with grpc client in mod_wsgi.

Thanks and Regards,

Manosh Padannayil

[Graham Dumpleton]

If you tried:

    WSGIApplicationGroup %{GLOBAL}

as mentioned in the documentation, then next try:

    https://modwsgi.readthedocs.io/en/master/user-guides/debugging-techniques.html#extracting-python-stack-traces

to get out stack traces as to where it is getting stuck.

Note you will need to update the code example in that doc to work with Python 3 as appears to still be for Python 2.

Graham

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