> On 7 Nov 2019, at 12:52 pm, ryan west <[email protected]> wrote:
>
> Hi Graham.
>
> Thanks very much for the prompt reply.
>
> When using a Python virtual environment with mod_wsgi, it is very important
> that it has been created using the same Python installation that mod_wsgi was
> originally compiled for. It is not possible to use a Python virtual
> environment to force mod_wsgi to use a different Python version, or even a
> different Python installation.
>
> You cannot for example force mod_wsgi to use a Python virtual environment
> created using Python 3.5 when mod_wsgi was originally compiled for Python
> 2.7. This is because the Python library for the Python installation it was
> originally compiled against is linked directly into the mod_wsgi module. In
> other words, Python is embedded within mod_wsgi. When mod_wsgi is used it
> does not run the command line python program to run the interpreter and thus
> why you can’t force it to use a different Python installation.
>
>
> After reading this, I still find myself a bit confused as to what is
> happening under the hood, though I suspect that this is a gap in my knowledge
> rather than a deficiency in the documentation. If I am in a virtualenv for a
> specific version of python, wouldn't a pip install mod-wsgi install a version
> of the module that is compiled against a similar version of python? It seems
> like a reasonable assumption, and one that generally speaking has worked well
> for me.
The problem I see is that you have said you have two virtual environments of:
• /home/release/envs/stage-python2.7
• /home/release/envs/stage-python3.6
You may have a symlink to one or the other, but how are you controlling which
mod_wsgi module is being loaded by Apache using the LoadModule line.
That LoadModule line is going to have to be to a file inside of the
site-packages directory of the respective virtual environment when switch
between them, but that directory path has a further directory (below those root
directories for the virtual environment), which has the Python version in it.
Eg:
/home/release/envs/stage-python2.7/lib/python2.7/site-packages/mod_wsgi/.....
/home/release/envs/stage-python3.6/lib/python3.6/site-packages/mod_wsgi/.....
So just changing the symlink to the root of the virtual environment is not
enough, the LoadModule line in Apache would also need to change.
This suggests the LoadModule line is loading a system Python version, possibly
Python 2.7. Which means that when change the stage link to 3.6 it will fail, as
will be still running Python 2.7, but can't find all the 2.7 files in the
Python 3.6 virtual environment since no lib/python2.7 directory exists. Thus
why site module fails to load.
> In my use-case, I do not need to run the application in python 2 and 3
> simultaneously, side-by-side on the same instance. It is completely
> acceptable for me to have either or. Do you still recommend using
> mod_wsgi-express?
>
> Thanks again Graham. I will more thoroughly review the documentation page
> that you linked below.
>
> Ryan
>
> On Wednesday, November 6, 2019 at 5:03:41 PM UTC-8, Graham Dumpleton wrote:
> Ensure you have read:
>
> https://modwsgi.readthedocs.io/en/develop/user-guides/virtual-environments.html
>
> <https://modwsgi.readthedocs.io/en/develop/user-guides/virtual-environments.html>
>
> The mod_wsgi module has to be compiled for the Python version you want to use
> as it links to the Python library, the Python executable is never itself run.
> You cannot use mod_wsgi compiled for a specific Python version with virtual
> environments for a different Python version.
>
>> On 7 Nov 2019, at 11:54 am, ryan west <[email protected] <>> wrote:
>>
>> Hello,
>>
>> I've spent a fair bit of time diagnosing this particular issue with
>> Apache/mod_wsgi and could use some pointers. Any help is extremely
>> appreciated.
>>
>> Versions
>> Ubuntu 14.04.6 LTS
>> Python 2.7.8
>> Python 3.6.8
>> mod-wsgi 4.3.2 (installed via pip)
>> Virtualenvs
>> /home/release/envs/stage-python2.7
>> /home/release/envs/stage-python3.6
>> Depending on which version of python I want this instance to use, a symlink
>> is created at /home/release/envs/stage that maps to either of the
>> virtualenvs above. In this example, I am simply trying to get it working
>> with python 2.7.
>
> You can't do that.
>
> Suggest you use mod_wsgi-express instead and run separate instances of that
> for each Python version and then as necessary use the main system Apache to
> proxy to those separate instances.
>
>>
>> Apache Logs
>>
>> ryanwest@el8-stage-experimental-webapp1:/home/release/envs$ sudo tail
>> /var/log/apache2/error.log
>> [Wed Nov 06 16:38:51.586673 2019] [:info] [pid 2978:tid 139776709330816]
>> mod_wsgi (pid=2978): Python home /home/release/envs/stage/bin.
>> [Wed Nov 06 16:38:51.586681 2019] [:info] [pid 2978:tid 139776709330816]
>> mod_wsgi (pid=2978): Initializing Python.
>> [Wed Nov 06 16:38:51.585441 2019] [:info] [pid 2976:tid 139776709330816]
>> mod_wsgi (pid=2976): Starting process 'http.www.stage.domain.com
>> <http://http.www.stage.domain.com/>' with uid=33, gid=33 and threads=1.
>> [Wed Nov 06 16:38:51.588878 2019] [:info] [pid 2976:tid 139776709330816]
>> mod_wsgi (pid=2976): Python home /home/release/envs/stage/bin.
>> [Wed Nov 06 16:38:51.588886 2019] [:info] [pid 2976:tid 139776709330816]
>> mod_wsgi (pid=2976): Initializing Python.
>> [Wed Nov 06 16:38:51.589546 2019] [:info] [pid 2973:tid 139776709330816]
>> mod_wsgi (pid=2973): Python home /home/release/envs/stage/bin.
>> [Wed Nov 06 16:38:51.589559 2019] [:info] [pid 2973:tid 139776709330816]
>> mod_wsgi (pid=2973): Initializing Python.
>> ImportError: No module named site
>> ImportError: No module named site
>> ImportError: No module named site
>
> The error is specifically because you are mixing Python versions.
>
>> Apache Conf (/etc/apache2/sites-available/stage.conf)
>> ryanwest@el8-stage-experimental-webapp1:/home/release/envs$ cat
>> /etc/apache2/sites-available/stage.conf
>> # LB TERMINATED
>> <VirtualHost *:80>
>>
>> # apache default of 8190 is too small because we have some long uri
>> LimitRequestLine 81900
>>
>> ServerName www.stage.domain.com
>>
>> DocumentRoot "/opt/domain/sites/www.stage.domain.com/current
>> <http://www.stage.domain.com/current>"
>>
>> ErrorLog "/var/log/domain/www.stage.domain.com/www.error.django.log
>> <http://www.stage.domain.com/www.error.django.log>"
>>
>> LogLevel debug
>>
>> WSGIDaemonProcess http.www.stage.domain.com user=www-data
>> maximum-requests=5000 processes=30 threads=1 python-eggs=/tmp
>> display-name='%{GROUP}' python-home=/home/release/envs/stage/bin
>> WSGIProcessGroup http.www.stage.domain.com
>> WSGIApplicationGroup http.www.stage.domain.com
>> WSGIImportScript /opt/domain/sites/www.stage.domain.com/wsgi_imports.py
>> process-group=http.www.stage.domain.com
>> application-group=http.www.stage.domain.com
>> WSGIScriptAlias / /opt/domain/sites/www.stage.domain.com/virtualenv.wsgi
>> # APP-8453: WSGI doesn't pass through auth headers by default
>> WSGIPassAuthorization On
>>
>> XSendFile on
>> XSendFilePath /mnt/www.stage.domain.com/media
>> XSendFilePath /opt/domain/sites/www.stage.domain.com/current/media
>>
>> RewriteEngine on
>> ProxyRequests On
>> SSLProxyEngine on
>>
>> RewriteCond %{DOCUMENT_ROOT}/downtime-enabled.html -l
>> RewriteCond %{REQUEST_URI} !\.(css|jpg|gif|png)$
>> RewriteCond %{HTTP_HOST} !^\w+1\.
>> RewriteCond %{SCRIPT_FILENAME} !downtime-enabled.html
>> RewriteRule ^.*$ %{DOCUMENT_ROOT}/downtime-enabled.html [L]
>>
>> </VirtualHost>
>>
>> In this case, /home/release/envs/stage is a symlink to a python2.7
>> virtualenv:
>>
>> ryanwest@el8-stage-experimental-webapp1:/home/release/envs$ ls -l
>> total 8
>> lrwxrwxrwx 1 root root 34 Nov 6 12:11 stage ->
>> /home/release/envs/stage-python2.7
>> drwxr-xr-x 6 release root 4096 Nov 6 15:41 stage-python2.7
>> drwxr-xr-x 4 release root 4096 Nov 6 12:10 stage-python3.6
>>
>> ryanwest@el8-stage-experimental-webapp1:/home/release/envs$ ls -l
>> stage-python2.7
>> total 16
>> drwxr-xr-x 2 release root 4096 Nov 6 14:27 bin
>> drwxr-xr-x 2 release root 4096 Nov 6 12:10 include
>> drwxr-xr-x 3 release root 4096 Nov 6 12:10 lib
>> drwxr-xr-x 3 root root 4096 Nov 6 12:15 man
>>
>> ryanwest@el8-stage-experimental-webapp1:/home/release/envs$
>> stage-python2.7/bin/python --version
>> Python 2.7.8
>> ryanwest@el8-stage-experimental-webapp1:/home/release/envs$
>> stage-python3.6/bin/python --version
>> Python 3.6.8
>>
>> I realize that pointing python-home to the bin directory is strange. When I
>> point it to simply /home/release/envs/stage, the apache error logs default
>> to saying python home is /usr/bin/python.
>
> The Python executable is never invoked. What the location is reported as
> within the process doesn't matter.
>
>> As a side note, my Apache logs don't seem to be providing me with many
>> pertinent details. I have tried increasing the verbosity using LogLevel
>> debug with no success.
>>
>> What am I doing wrong? Thank you!
>>
>> Ryan
>>
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