crontab-client

* * * * * wget -O /dev/null -q http://server/cgi-bin/imalive.py

crontab-server

# m h  dom mon dow   command
* 9-18 * * 1-5 /usr/lib/cgi-bin/imalive.py

imalive.py

#!/usr/bin/python
import time
import os
import sys
import smtplib
from email.MIMEText import MIMEText
from email.Utils import formatdate

CHECKFILE="/tmp/imalive"
THRESHOLD=60 * 5
GMAIL_ID="your_gmail_id@gmail.com"
GMAIL_PASSWORD="your_gmail_password"
RECIPIENT="alert_recipient@example.com"

def create_message(from_addr, to_addr, subject, body):
    msg = MIMEText(body)
    msg['Subject'] = subject
    msg['From'] = from_addr
    msg['To'] = to_addr
    msg['Date'] = formatdate()
    return msg

def send_via_gmail(from_addr, to_addr, msg):
    s = smtplib.SMTP('smtp.gmail.com', 587)
    s.ehlo()
    s.starttls()
    s.ehlo()
    s.login(GMAIL_ID, GMAIL_PASSWORD)
    s.sendmail(from_addr, [to_addr], msg.as_string())
    s.close()

def cgi():
    if not os.path.exists(CHECKFILE):
        msg = create_message(GMAIL_ID, RECIPIENT, "Facility alert (recovered)", "Recovered from failing status.")
        send_via_gmail(GMAIL_ID, RECIPIENT, msg)
    os.system("touch %s" % CHECKFILE)
    print "Content-type: text/plain\n"
    print "OK"

def check():
    if not os.path.exists(CHECKFILE): return
    if time.time() - os.stat(CHECKFILE).st_mtime < THRESHOLD: return
    os.unlink(CHECKFILE)
    msg = create_message(GMAIL_ID, RECIPIENT, "Facility alert (failed)", "Internet disconnected or server down.")
    send_via_gmail(GMAIL_ID, RECIPIENT, msg)
    
if __name__ == '__main__':
    if "REQUEST_METHOD" in os.environ: cgi()
    else: check()