Sentinel Monitoring: Is your server down
I remember the first time I received a text message indicating my server was down. I was at a ball game with friends and immediately phoned someone to check into it. Within a few minutes we resolved the issue and got everything back online. It followed the stages of panic, stress, anxiety, and then relief once the situation was over.
Over time you get better at dealing with these inevitable outages. First you freak out over every little thing, then eventually you learn to take them in stride. Now in the rare instances the server has a hiccup I just contact the tech department of our hosting service and go back to enjoying the burrito I was eating.
Having a website monitoring service is important. Websites are online 24×7 every day of the year. Invariably the server will crash at some point. Whether the disc is out of space, OS is frozen, or network connectivity is down, there will be times when the website just conks out. Not all website monitoring services are created equal however. Most will only tell you if the server is offline and send you a message as soon as an error is detected. Sentinel Monitoring is a new service that offers a complete set of fully customizable server monitoring tools.
The primary feature offered by all server monitoring tools is to ping your machine. It sends out packets, receives them, and verifies the machine is a least online. Sentinel takes ping to the next level, allowing you to set various parameters such has how much latency to accept. That is, how long should it wait to receive the packets until it declares the server offline. Then you can indicate what percentage of packets you require to be received and how many packets to send. For instance, if it’s known that a network connection is spotty, the amount of packets can be increased and a lower success rate be required. On top of that it will check multiple times prior to sending out a warning messages. All these advanced settings give the user the ability to configure Sentinel so it’s less likely to send false alarms.
Sentinel doesn’t stop with pinging your machine though. They support checking services including http, https, certificates, smtp (email), pop3 (more email), ftp, imap, dns, ssh, streams (video and audio streams, Icecast and Shoutcast), and then they provide a generic tcp service checker. If these don’t make sense to everyone, think of them as the core functions required to keep a website happy and online. Of interest is http, in that you can configure more than just your home page. It can check any number of pages within your site to ensure the page loads and is online. Each has configurable options specific to that service, ranging from adjusting the port number to the frequency the service will be checked.
Sentinel’s offering isn’t limited to checking services that can be accessed externally. The platform is integrated with an agent that can be installed locally, to gather information about the machine itself. The agent used is Nagios, the industry standard for open source server monitoring. I can be installed on linux or windows. This allows you to monitor when disc space is running low, if the load is too high, or if a specific process is running. It also checks swap space, which is used for memory management, or NTP, which is a mysterious service shrouded in controversy and intrigue. Little is known about it. (It actually stands for network time protocol and ensures your server’s clocks are in sync.)
If all this sounds confusing, fear not. The core usage of Sentinel is as easy as registering and typing in your domain name. The advanced options default to reasonable settings and don’t immeditiately need to be adjusted. The notifications come in the form of emails, texts, direct messages from Twitter, or can be configured with an iPhone app. Sentinel also provides you the courtesy of a follow up email indicating your server is back online. This prevents you from getting back to the server only to learn it’s already taken care of.
Sentinel is extremely cost effective for a best of brand service. It’s free for the first month and then $10/month thereafter. These are New Zealand dollars, which makes it closer to 5 euros a month or 7USD with current exchange rates. Three servers can be checked with the core package and more can be added individually or with bulk discounts. Notably, it allows you to check as many services as suits your needs. Also notably, you can add other users to give the entire team access.
Sentinel offers a simple yet dynamic tool to monitor your websites. Its user friendly design makes it easy for basic set up as well as advanced configurations. The integration of the local agent gives you full access to all the system information you need. Sentinel is the new way web masters will be monitoring their sites. Which will leave plenty more time for burritos for all of us.
Sentinel’s fine service has announced that it’s refocusing. We don’t know if refocusing means having a few pints down at the pub, or working away on their next stroke of brilliance. We have high aspirations for them though.