I am trying to move away from embedded and configuring the apache2 (not
mod_wsgi embedded), virtual hosts but keep getting this issue of Symbol Not
found , Expected in flat namespace.
I added following virtualhost config.
<VirtualHost *:80>
ServerAdmin [email protected]
ServerName www.groc-example.com
ServerAlias groc-example.com
WSGIScriptAlias /images/ /var/www/images/wsgiimagehandler.py
ErrorLog "/private/var/log/apache2/image_error_log"
CustomLog "/private/var/log/apache2/image_custom_log" common
WSGIDaemonProcess images python-home=/users/vishnu/anaconda
python-path=/var/www/images/ processes=1 threads=10 inactivity-timeout=30
maximum-requests=20
WSGIProcessGroup images
WSGIApplicationGroup %{GLOBAL}
<Directory "/var/www/images/">
Options +ExecCGI
Allow from all
Require all granted
</Directory>
</VirtualHost>
I added LoadModule wsgi_module
"/Users/vishnuhari/anaconda/lib/python2.7/site-packages/mod_wsgi/server/mod_wsgi-py27.so"
in
the httpd.conf.
Also uncommented the line which has following
LoadModule cgi_module libexec/apache2/mod_cgi.so
Include /private/etc/apache2/extra/httpd-vhosts.conf
After i did tha above, have restarted and start apachectl,
ERROR :
[Fri Apr 07 22:26:25.838308 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] File
"/users/vishnu/anaconda/lib/python2.7/mimetools.py", line 6, in <module>
[Fri Apr 07 22:26:25.838389 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] import tempfile
[Fri Apr 07 22:26:25.838398 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] File "/users/vishnu/anaconda/lib/python2.7/tempfile.py",
line 32, in <module>
[Fri Apr 07 22:26:25.838535 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] import io as _io
[Fri Apr 07 22:26:25.838544 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] File "/users/vishnu/anaconda/lib/python2.7/io.py", line
51, in <module>
[Fri Apr 07 22:26:25.838615 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] import _io
[Fri Apr 07 22:26:25.838635 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] ImportError:
dlopen(/users/vishnuhari/anaconda/lib/python2.7/lib-dynload/_io.so, 2):
Symbol not found: __PyCodecInfo_GetIncrementalDecoder
[Fri Apr 07 22:26:25.838640 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] Referenced from:
/users/vishnuhari/anaconda/lib/python2.7/lib-dynload/_io.so
[Fri Apr 07 22:26:25.838643 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] Expected in: flat namespace
[Fri Apr 07 22:26:25.838646 2017] [wsgi:error] [pid 1634] [remote
127.0.0.1:54121] in
/users/vishnuhari/anaconda/lib/python2.7/lib-dynload/_io.so
On Friday, April 7, 2017 at 1:05:26 PM UTC+5:30, Vishnu Prasad wrote:
>
> Graham, Thanks a ton for the response.
>
> I have updated more inputs inline for your review and suggestions.
>
> thanks
>
> On Friday, April 7, 2017 at 8:57:22 AM UTC+5:30, Graham Dumpleton wrote:
>>
>>
>> On 7 Apr 2017, at 9:40 AM, Vishnu Prasad <[email protected]> wrote:
>>
>> All,
>> I am new to mod_wsgi and the entire configurations around related to
>> this. Detailing out the requirement, please do let me know your response.
>>
>> 1. I have written a simple python script to handle images which listens
>> on port 8041. There is some custom processing happening here and its not
>> just static rendering. The output of this is a content of type image and
>> bytes is the response.
>> 2. I am starting this python script file(application) using command
>> mod_wsgi-express start-server abc.py --threads 20 --process 2
>>
>>
>> Are you doing image processing? If you are and it is CPU intensive, then
>> use of threads, rather than processes, isn't then best idea.
>>
> [Vishnu:] Yes, am using Pillow-SIMD to dynamically generate or resize
> images for optimize image rendering. Once returned from here, caching in
> varnish. We have over 100,000 items to process and at any given point
> easily and i will need to generate about 20-30 images/sec. This webserver
> cluster is about 4 and sitting behind LB. I have done image domain
> randomization to leverage capability of browsers to download more parallel
> images. Created about 3 subdomains for this as well, hence processes of 2.
> Agree - Once performance tested we may tune this further. Further this
> webserver is dedicated to passthrough request to next level appserver
> outside of which this is the only CPU intense process working on these.
>
>>
>> 3. I have varnish script that whenever gets any requests for images on
>> 8080 routes to this application on port 8041.
>> 4. This application is also running another default instance of apache2
>> which is serving my all other application requests not related to images.
>>
>>
>> And this is a Python application also hosted on mod_wsgi, but configured
>> manually in normal Apache instance rather than using mod_wsgi-express?
>> [Vishnu:] Yes, this is on mod_wsgi but not configured through normal
>> apache instance. As you said in one of your blog, getting it working was
>> first - so started in embedded mode and now reviewing if I should move out
>> or keep it that way for one set of URL's. This means all images goes to
>> mod_wsgi-express and others go to the normal apache default instance.
>> Earlier I thought of having a virtualhost config to route this for all
>> /image patterns i.e. Daemon config as you said in one of the blog, later
>> realized about the modularity of this setup. I wanted to use this as
>> stand-alone modular imageserver. I am reading through your link below on
>> the issues with embedded mode of running. I will review both these options
>> and run some performance tests. This is helpful.
>>
>> The above setup is working.
>>
>> Problem/Help needed:
>> 1. I want to configure and run the above application as distinct
>> WSGIDaemonProcess. How do I achieve this ?
>>
>>
>> If for (4) you are running a Python application hosted on mod_wsgi, you
>> should already be using daemon mode as embedded node is generally not
>> recommended as explained in:
>>
>>
>> http://blog.dscpl.com.au/2012/10/why-are-you-using-embedded-mode-of.html
>> <http://www.google.com/url?q=http%3A%2F%2Fblog.dscpl.com.au%2F2012%2F10%2Fwhy-are-you-using-embedded-mode-of.html&sa=D&sntz=1&usg=AFQjCNGiURKOSUfshe-g4r-68VMGRnLOYQ>
>>
> [Vishnu:] I am running this app in embedded mode as i was planning to use
> this more to manage/handle only image requests.
>
>>
>> 2. If the above ask is accomplished by a configuration in default apache
>> httpd.conf (not mod_wsgi httpd.conf) then i also want to know how will
>> apache identify my application vs other applications of mod_wsgi which may
>> be running ? Is it based on server url or ?
>>
>>
>> How to vertically partition a URL namespace so as to directory subsets of
>> URLs to a different daemon process group within the same Apache instance,
>> is explained in:
>>
>>
>> http://blog.dscpl.com.au/2014/02/vertically-partitioning-python-web.html
>> <http://www.google.com/url?q=http%3A%2F%2Fblog.dscpl.com.au%2F2014%2F02%2Fvertically-partitioning-python-web.html&sa=D&sntz=1&usg=AFQjCNFSqPozGdQVlEtWMQUYSzWo1LEzOQ>
>>
>> 3. For the above application, need to have better control over what is
>> loaded in httpd.conf. So, want to load my own httpd.conf including path of
>> log mounts etc. How do I achieve this ?
>>
>> [Vishnu:] My question was how do i specifically setup a httpd.conf for
>> this embedded mode i.e. outside the core apache2 installation. Based on
>> what i read from you its better to not run in embedded mode. However, if
>> we need to then the configuration around logs for this specifically will
>> need to happen in mod_wsgi hence the ask.
>>
> Again, am not generating apache config instead am asking how do i tell
> mod_wsgi-express, instead of you reading from /tmp/....httpd.conf, read
> this from /usr/local/httpd.conf ? Is there some server-base path setting
> which i could use and set this or ? I completely understand your point and
> dont want to mess up over-engineering the solution.
>
>>
>> I don't understand what you mean by this.
>>
>> You should not be using mod_wsgi-express to generate Apache configuration
>> to then use in an existing Apache installation. The mod_wsgi-express
>> instance is self contained with a generated configuration. If
>> customisations for that are required, most common things can be overridden
>> using the command line options. For some special cases you can use
>> --include-file to add additional configuration at the end of the generated
>> configuration if necessary.
>>
>
>
>
> 4. Finally, at somepoint if I want to manage the httpd.conf common file
>> across WSGI and my default apache, how do I set up the application specific
>> configurations - through virtualhost section in httpd-vhost.conf or ?
>>
>>
>> If for the other (4) above the answer is that you are also using a
>> manually configure Apache/mod_wsgi, as well as a separate mod_wsgi-express
>> for just one subset of URLs, then as per blog on vertically partition, you
>> probably should just do it all manually in one Apache/mod_wsgi instance if
>> want to have config all in one spot. Personally I would probably use
>> multiple mod_wsgi-express instance sitting directly behind varnish or
>> whatever front end you are using. The generated configuration from
>> mod_wsgi-express is usually going to be better than what many would set up
>> manually as it sets a whole lot of good stuff related to timeouts which
>> makes things more robust. When Apache/mod_wsgi is manually configured there
>> are no default timeouts set.
>>
> [Vishnu:] Understand that you suggest against embdedded mode and against
> managing 2 apache conf files. Even if we need, then you suggest me to take
> just mod_wsgi-express. I will review this as said earlier as well. Also, i
> went through the httpd.conf of mod_wsgi process for WSGIDaemon node and its
> quite extensive. I will keep you posted on the outcome. thanks a ton for a
> detailed answer, the links are helpful and am reading through them for
> guidance.
>
>>
>> Anyway, suggest you read that blog on vertically partition a web
>> application at least and clarify things by answering questions above.
>>
>> Graham
>>
>
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