Today I had a small revelation.
I was wracking my brains trying to figure out the SMS messaging provider to use to send myself service outage notifications for my clients’ web sites. Given that I have just a handful of clients so far, it makes no sense to use a provider that requires a minimum monthly or yearly spend.
Ideally of course, I’d like to spend nothing at all, and in exasperation I finally threw my hands in the air (they’re detachable) and whined: “Google sends SMS’s for free - why is it so hard for everyone else?”
(answer: not everyone has billions of dollars)
And then came the revelation: Why not create a command-line tool that uses Google’s Calendar API to create events 6 minutes in the future that have an SMS notification set for 5 minutes prior to launch? That way, within a minute you get a notification sent to your phone for free within 1 minute. Sweet!
So, here’s the code (it’s in Java… sorry)
/**
* Simple command-line notification command that uses Google Calendar ATOM API to create
* a single event 6 minutes in the future with a 5 minute SMS reminder
*
* @author Daniel Walmsley
*
*/
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Date;
import java.util.List;
import com.google.gdata.client.calendar.CalendarService;
import com.google.gdata.data.DateTime;
import com.google.gdata.data.PlainTextConstruct;
import com.google.gdata.data.calendar.CalendarEntry;
import com.google.gdata.data.calendar.CalendarEventEntry;
import com.google.gdata.data.calendar.CalendarFeed;
import com.google.gdata.data.extensions.Reminder;
import com.google.gdata.data.extensions.When;
import com.google.gdata.data.extensions.Reminder.Method;
import com.google.gdata.util.AuthenticationException;
import com.google.gdata.util.ServiceException;
/**
* This is a test template
*/
public class GCalNotifier {
public static void main(String[] args) {
/**
* Command line args:
*
* username
* password
* calendar name (e.g. “Notifications”)
* TimeZone offset (in hours)
* event start offset (in minutes)
* event end offset (in minutes)
* title
* description
*/
try {
// Create a new Calendar service
CalendarService myService = new CalendarService(”GCal Event Notifier”);
myService.setUserCredentials(args[0], args[1]);
String calendarName = args[2];
Long tzOffset = new Double(Double.parseDouble(args[3])).longValue() * 60 * 60 * 1000;
Long startOffset = new Integer(Integer.parseInt(args[4])).longValue() * 60 * 1000;
Long endOffset = new Integer(Integer.parseInt(args[5])).longValue() * 60 * 1000;
String title = args[6];
String description = args[7];
// Get a list of all entries
URL metafeedUrl = new URL(
“http://www.google.com/calendar/feeds/default/allcalendars/full”);
System.out.println(”Getting Calendar entries…\n”);
CalendarFeed resultFeed = myService.getFeed(metafeedUrl,
CalendarFeed.class);
List entries = resultFeed.getEntries();
for (int i = 0; i < entries.size(); i++) {
CalendarEntry entry = entries.get(i);
String currCalendarName = entry.getTitle().getPlainText();
System.out.println("\t" + currCalendarName);
if (currCalendarName.equals(calendarName)) {
sendDowntimeAlert(myService, entry,
title, description, startOffset, endOffset, tzOffset);
}
}
System.out.println("\nTotal Entries: " + entries.size());
} catch (AuthenticationException e) {
e.printStackTrace();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (ServiceException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private static void sendDowntimeAlert(CalendarService myService,
CalendarEntry entry, String title, String description, Long startOffset, Long endOffset, Long tzOffset) throws IOException,
ServiceException {
String postUrlString = entry.getLink("alternate", "application/atom+xml").getHref();
URL postUrl = new URL(postUrlString);//was: "http://www.google.com/calendar/feeds/jo@gmail.com/private/full"
CalendarEventEntry myEntry = new CalendarEventEntry();
myEntry.setTitle(new PlainTextConstruct(title));
myEntry.setContent(new PlainTextConstruct(description));
Date now = new Date();
Date startDate = new Date(now.getTime()+startOffset);
Date endDate = new Date(now.getTime()+endOffset);
DateTime startTime = new DateTime(startDate.getTime()+tzOffset);
DateTime endTime = new DateTime(endDate.getTime()+tzOffset);
When eventTimes = new When();
eventTimes.setStartTime(startTime);
eventTimes.setEndTime(endTime);
myEntry.addTime(eventTimes);
// Send the request and receive the response:
CalendarEventEntry insertedEntry = myService.insert(postUrl, myEntry);
System.err.println("Got response for: "+insertedEntry.getTitle().getPlainText());
for(When when : insertedEntry.getTimes()) {
System.err.println("When: "+when.getStartTime()+" to "+when.getEndTime());
}
//5 minute reminder
Reminder reminder = new Reminder();
reminder.setMinutes(5);
reminder.setMethod(Method.SMS);
insertedEntry.getReminder().add(reminder);
insertedEntry.update();
}
}
Don’t forget, you’ll need to download the Google Data APIs and put their JARs in your classpath before this will work!
Personally I use this with Nagios. I always use the same args for the calendar offsets, so I’ve encapsulated most of my settings (except title and body) in a script.
#!/bin/sh
export SCRIPTDIR=/opt/calAlert
export USERNAME=username@gmail.com
export PW=mySecurePassword
export CAL=Notifications
export TZOFFSET=10
export STARTOFFSET=7
export ENDOFFSET=12
export TITLE=$1
export BODY=$2
#export CURRDIR=`pwd`
export CLASSPATH="${SCRIPTDIR}/calAlert.jar"
#assumes GData libs are in "libs" subdirectory of SCRIPTDIR
for jarfile in $(ls "${SCRIPTDIR}/lib")
do
CLASSPATH="${CLASSPATH}:${SCRIPTDIR}/lib/${jarfile}"
echo lib/${jarfile}
done
echo "CLASSPATH=${CLASSPATH}"
export CLASSPATH
java GCalNotifier ${USERNAME} ${PW} ${CAL} ${TZOFFSET} ${STARTOFFSET} ${ENDOFFSET} "${TITLE}" "${BODY}"
