Changes between Initial Version and Version 1 of UoL LAMP HowTo Install Legacy Python Flask Applications

Timestamp:

10/10/18 14:56:09 (6 years ago)

Author:

Richard Bramley

Comment:

--

UoL LAMP HowTo Install Legacy Python Flask Applications

@@ +1 @@
+= UoL LAMP HowTo Install Python Flask Applications
+
+Tags: [[HowTo]] [[Install]] [[Pain in the proverbial]] [[UoL LAMP Server]]
+
+== Python 2
+
+=== Difficulties
+
+This installations is made more difficult by 3 things:
+
+1. Suse Linux does not have mod_wsgi in its repositories, so you're going to have to compile it.
+2. mod_wsgi seems picky about where it picks python apps and libraries from
+3. The LAMP servers don't put things where you'd expect them to be.
+4. Some other stuff that I don't quite understand
+
+=== Requirements
+
+Before installation can start, the following packages will have to be installed by IT services:
+
+- libmysqlclient-dev
+- python-dev
+
+=== Start Services
+
+Start the Apache and MySQL and make sure that they are restarted when the server is rebooted.
+
+{{{
+sudo /sbin/chkconfig uol.apache2 on
+sudo /etc/init.d/uol.apache2 start
+sudo /sbin/chkconfig uol.mysql on
+sudo /etc/init.d/uol.mysql start
+}}}
+
+=== Proceduce
+
+1. Install {{{mod_wsgi.so}}} into the directory {{{/local/apache2/etc/}}}
+ 1. Compile `mod_wsgi`. See: [[HowTo Compile mod_wsgi for LAMP servers]]
+ 2. Copy `mod_wsgi.so` from the directory {{{/local/apache2/etc/}}} of an existing UoL LAMP python Flask application.
+2. Clone the application from the `git` repository into `/local/` directory.
+3. Install virtualenv:
+ a. First switch to python 2.7 by running the command `source /opt/python2/etc/python-env.sh`
+
+{{{
+easy_install --install-dir=/local/python virtualenv
+}}}
+
+    ''For some reason that I can't work out (point 4. above), it would only pick up some of the python libraries from a virtual env and not when they were installed in `/local/python/`.  Maybe this was because of the order that I installed things, but I couldn't get it to work without the virtual environment.''
+4. Create a virtual environment in the application directory.
+
+{{{
+cd /local/{application directory}
+/local/python/virtualenv --no-site-packages BASELINE
+}}}
+
+    ''`BASELINE` is the name of the virtual environment.  It could be called anything, but it's called that!  Also note that you need to use the full path to the `virtualenv` utility, since `/local/python` isn't in `$PATH`.''
+
+5. Activate the environment, install the required packages, then deactivate.  This example shows some common requirements:
+
+{{{
+source BASELINE/bin/activate
+easy_install flask
+easy_install flask-sqlalchemy
+easy_install mysql-python
+easy_install flask-wtf
+easy_install WTForms-Components
+deactivate
+}}}
+
+6. Load the WSGI module into Apache, by editing the file `/local/apache2/etc/loadmodule.conf` by adding this line at the end.
+
+{{{
+LoadModule wsgi_module /local/apache2/etc/mod_wsgi.so
+}}}
+
+7. Add the WSGI config to the Apache config file `/local/apache2/etc/httpd.conf`:
+
+{{{
+<Directory /local/{application directory}>
+    WSGIProcessGroup {application name}
+    WSGIApplicationGroup %{GLOBAL}
+    Order deny,allow
+    Allow from all
+</Directory>
+
+WSGIDaemonProcess {application name} user=wwwrun threads=5 python-path=/local/{application directory}/BASELINE/lib/python2.6/site-packages:/local/python:/usr/lib64/python2.6/site-packages:/usr/share/doc/packages/ home=/local/{application directory}/
+WSGIScriptAlias / /local/{application directory}/{path to *.wsgi}
+}}}
+
+    ''The two hard won things here are the values for the `python-path` and `home` arguments.  The `python-path` must contain every directory where python libraries are installed, including a sub-directory of the virtualenv directory you created earlier.  The `home` must point to your application directory, or you won't be able to pick up your own modules.''
+
+8. Restart apache:
+
+{{{
+sudo /etc/init.d/uol.apache2 restart
+}}}
+
+9. Create any databases that are required and given the appropriate user permissions.
+
+10. Update the application settings in {{{/local/{application directory} }}}
+
+10. Pray.
+
+== Other Possible Stuff (**Not required last time used!**)
+
+1. You may need to give `wwwrun` extra permissions to the `/local/{application directory}` directory.
+2. You might need to pray a bit more.
+
+{{{
+setfacl -m u:wwwrun:rwx /local/{application directory}
+setfacl -m d:u:wwwrun:rwx /local/telomere/{application directory}
+}}}
+
+=== Gotchas
+
+- [[Python Flask Gotchas Import Database Module Fails]]
+
+[[BackLinks]]