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Sendmail/STARTTLS verify=FAIL

Oct 19 14:04:34 Billing sm-mta[17583]: STARTTLS=client,, version=TLSv1/SSLv3, verify=FAIL, cipher=ECDHE-RSA-RC4-SHA, bits=128/128

If you see those errors in your mail.log and your emails are failing to send, you need to add your ssl cert from apache to the sendmail config in /etc/mail/
# CA directory
O CACertPath=/etc/apache2/ssl
# CA file
O CACertFile=/etc/apache2/ssl/
# Server Cert
O ServerCertFile=/etc/apache2/ssl/example.cert
# Server private key
O ServerKeyFile=/etc/apache2/ssl/example.key

Adding Virtualhost In Apache For Port

Say we wanted to route the <your-domain>.com:8072/misc to /var/www/misc...

Add the following to /etc/apache2/ports.conf:
NameVirtualHost *:8072
Listen 8072

Add a file that describes your site to /etc/apache2/sites-available with this:
<VirtualHost *:8072>
   ServerName <your-domain>.com
   DocumentRoot /var/www/misc/

Run this command: sudo a2ensite misc

And restart apache: sudo service apache2 restart

Deploying Nginx + Gunicorn + Flask

Why use both Nginx and Gunicorn?:

Simple explanation:

Nginx SSL configuration:

The thing I spent the longest on was getting supervisor to work. Gunicorn kept giving me "gunicorn.errors.HaltServer: <HaltServer 'Worker failed to boot.' 3>", because I was missing the "directory" parameter. I needed to tell supervisor which directory to start from.

command=/<path>/venv/prod/bin/gunicorn -w 8 main:app -b

You will need to create an upstart script to get supervisor to run when the system starts:

Python Excel Library Benchmark Comparison

benchmark_csv                  0.026495
benchmark_excellent            1.784107
benchmark_openpyxl             2.897072
benchmark_openpyxl_rows        7.025895
benchmark_pyexcelerate         0.550225
benchmark_xlsxcessive          1.430242
benchmark_xlsxwriter           1.611668
benchmark_xlwt                 1.275144

pyexcelerate          :  10.11
xlwt                  :  15.67
xlsxwriter (optimised):  19.70
xlsxwriter            :  23.50
openpyxl   (optimised):  95.82
openpyxl              :  95.90

Large Dictionaries Not Released From Memory - Python + Ubuntu

I have a flask application running on Ubuntu which reads from a file and creates several large dictionaries. After the dictionaries are created and flask returns the request, the memory used for the dictionaries is not released back to the OS. This example shows the problem:

It's not really a Flask issue, but the Flask guys were super helpful when I asked why my large dictionary wasn't released from memory:

I dug even deeper and learned this is a Linux thing:
"Python returns memory to the OS on the heap (that allocates other objects than small objects) only on Windows, if you run on Linux, you can only see the total memory used by your program increase."

My solution:
Turning it into a function and running it as a separate process

If you want to go even deeper down the rabbit hole, read these: