Мониторинг веб-сайтов: Обеспечение доступности и производительности

Website monitoring is the process of testing and verifying that end users can interact with a website or web application as expected. Website monitoring are often used by businesses to ensure website uptime, performance, and functionality is as expected. Website monitoring companies provide organizations the ability to consistently monitor a website or server function and observe how it responds. The monitoring is often conducted from several locations around the world to a specific website, or server, to detect issues related to general Internet latency, and network hop issues, and to prevent false positives caused by local or inter connect problems. Monitoring companies generally report on these tests in a variety of reports, charts, and graphs. When an error is detected monitoring services send out alerts via email, SMS, phone, SNMP trap, a pager that may include diagnostic information, such as a network traceroute, code capture of a web page's HTML file, a screenshot of a webpage, and even a video of a website failing. These diagnostics allow network administrators and webmasters to correct issues faster. Monitoring gathers extensive data on website performance, such as load times, server response times, and page element performance that is often analyzed and used to further optimize website performance.

Monitoring is essential to ensure that a website is available to users, downtime is minimized, and performance can be optimized. Users that rely on a website or an application for work or pleasure will get frustrated or even stop using the application if it is not reliably available. Monitoring can cover many things that an application needs to function, like network connectivity, Domain Name System records, database connectivity, bandwidth, and computer resources like free RAM, CPU load, disk space, events, etc. Commonly measured metrics are response time and availability (or uptime), but consistency and reliability metrics are gaining popularity. Measuring a website's availability and reliability under various amounts of traffic is often referred to as load testing. Website monitoring also helps benchmark the website against the performance of a competitor to help determine how well a site is performing. Website speed is also used as a metric for search engine rankings. Website monitoring can be used to hold web hosting providers accountable for their service level agreements. Most web hosts offer a 99.9% uptime guarantee and when uptime is less than that, individuals can be refunded for the excessive downtime. Not all hosts will refund individuals for excessive downtime so one must become familiar with the terms of service of their host. Most paid website monitoring services will also offer security features such as virus and malware scanning which is of growing importance as websites become more complicated and integral to the business.

Availability Nines Downtime per year90%1 nine876 hours95%–438 hours99%2 nines87 hours, 36 minutes99.9%3 nines8 hours, 45 minutes, 36 seconds99.99%4 nines52 minutes, 33.6 seconds99.999%5 nines5 minutes, 15.36 seconds99.9999%6 nines31.68 seconds

A website monitoring service can check other internet protocols besides HTTP pages and HTTPS such as FTP, SMTP, POP3, ActiveSync, IMAP, DNS, SSH, Telnet, SSL, TCP, PING, UDP, SOAP, Domain Name Expiry, SSL Certificate Expiry and a range of ports. Monitoring frequency occurs at intervals of once every 4 hours to every 15 seconds. Typically, most website monitoring services test a server, or application, between a once per hour per once per minute. Advanced monitoring services capture browser interactions with websites using macro recorders, or browser add ons such as Selenium or iMacros. These services test a website by running a web browser through a typical website transaction (such as a shopping cart) or a custom scenario, in order to check for user experience issues, performance problems, and availability errors. Browser driven monitoring services detect not only network and server issues, but also webpage object issues (such as slow loading JavaScript, or third party hosted page elements). Implementation of time performance monitoring for the Apache HTTP Server is the mod arm4 module.

Users of website monitoring (typically network administrators, webmasters, web operations personnel) may monitor a single page of a website, but can also monitor a complete business process (often referred to as multi step transactions).

Website monitoring services usually have a number of servers around the globe – South America, Africa, North America, Europe, Africa, Asia, Australia and other locations. By having multiple servers in different geographic locations, a monitoring service can determine if a web server is available across continents over the Internet. Some vendors claim that the more locations the better picture of your website availability while others say that three globally distributed stations are sufficient and more stations do not give more information.

As the information brought by website monitoring services is in most cases urgent and may be of crucial importance, various notification methods, often known as "alerts" are used: e mail, IM, regular and cell phones, SMS, fax, pagers, Skype, RSS Feed, SNMP trap, URL notifications, etc.

The Website monitoring market is very competitive. There are 150+ active service providers and more than 100 are documented to have gone out of business. Most of the providers offer a free plan with low frequency monitoring. In recent years Synthetic Monitoring services have become widely available commercially, providing another vehicle to monitor the performance of specific web properties at a granular level.