Python deploy function using Fabric

Question

Simple task - deploy war-file from TeamCity agent to remote web-server.

I realized it with Fabric, because of it make readable output, and give opportunity to login via SSH with RSA-key. Also - during deploy - build agent must make some additional steps - create backup, stop-start Tomcat service etc.

URL to deploy to can be passed via variable on build-server.

import os
import sys
import time
from fabric.api import run, env, put
VAR_PREFIX = 'bamboo_'
"""Cloudlibrary functions"""
def deploy(logger, rds_basedir):
 """Deploy cloudlibrary.war to remote box, passed via BASE_URL"""
 logger.logger.info('Running cloudlibrary.war deploy')
 # file to deploy
 local_file = 'target/cloudlibrary.war'
 # local_file = 'd:\\RDS\\rdsmanager\\file.txt'
 # file will be created during backup command
 back_file = '/home/ec2-user/backups/cloudlibrary/cloudlibrary_%s.war' % time.strftime('%Y-%m-%d')
 # commands list
 status = 'sudo service tomcat7 status'
 backup = 'cp /var/lib/tomcat7/webapps/cloudlibrary.war %s' % back_file
 check_bkp = 'file %s' % back_file
 tomcat_kill = 'sudo kill -9 $(cat /var/run/tomcat7.pid)'
 tomcat_start = 'sudo /etc/init.d/tomcat7 start'
 try:
 base_url = os.environ[VAR_PREFIX + 'BASE_URL']
 logger.logger.info('\nURL found %s' % base_url)
 except KeyError:
 base_url = 'www.dev.domain.com'
 logger.logger.info('URL variable not found, will default - %s' % base_url)
 # Fabric connection settings
 env.host_string = base_url
 env.key_filename = [os.path.join(rds_basedir, '.ssh', 'rdsmanager_priv.openssh')]
 env.user = 'user'
 env.project_root = '/var/lib/tomcat7/webapps'
 logger.logger.info('Using URL: %s, user: %s, RDS-key: %s, Tomcat webapps: %s' % (env.host_string, env.user, env.key_filename[0], env.project_root))
 if os.path.isfile(local_file):
 # make backup of current cloudlibrary.war to ~/backup/cloulibrary
 run(backup)
 # if new file doesn't found - Fabric will exit
 run(check_bkp)
 # stop Omcat before put new war-file
 run(tomcat_kill)
 # put new builded war-file
 put(local_file, env.project_root)
 # start Tomcat
 run(tomcat_start)
 # cgeck it's status
 run(status)
 else:
 logger.logger.error('ERROR: file %s not found. Exit.' % local_file)
 sys.exit(1)

• Mast: Are you aware of the existence of ftplib?
• setevoy: @Mast um... no... but - there is also tasks to start/stop Tomcat, not only copy war-file... plus - authorization possible with RSA key only

Answer 1

1. Using % for string formatting is deprecated. You should be using str.format() instead. Here's how one would use str.format(): print "Hello {0}.".format("world"). str.format() also supports using keyword arguments. Here's an example of that: print "Hello {word}.".format(word="world").
2. Near the end of the function deploy, underneath the if block with the condition os.path.isfile(local_file), you have comments above every line. These are unnecessary and can be removed.
3. Finally, I'm not sure why you have square brackets, [], around the value of the variable env.key_filename. If these aren't needed, they can be removed.