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HTTP or HTTPS health checks

Last Updated: Mar 26, 2021

What are HTTP or HTTPS health checks?

HTTP or HTTPS health checks are used to monitor the required IP addresses and collect multiple metrics over HTTP or HTTPS. These metrics include the web server network accessibility, service availability, and first packet latency. If a monitored IP address is abnormal, the system blocks the abnormal IP address. If the IP address becomes normal, the system unblocks the IP address.

Features

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1 . Health Check Protocol

This parameter specifies a protocol over which the system uses to monitor the required IP addresses and collect multiple metrics. These metrics include the web server network accessibility, service availability, and first packet latency. We recommend that you select HTTP or HTTPS.

2 . Check interval

This parameter specifies an interval between health checks during HTTP or HTTPS monitoring. Default value: 1 minute. The Ultimate Edition supports a minimum interval of 15 seconds.

3 . Select a port

This parameter specifies a port number for the specified health check protocol. The system monitors the required IP address over HTTP or HTTPS and checks whether the specified port of a web server functions as expected. The default port number for HTTP is 80. The default port number for HTTPS is 443. You can also specify a custom port number for a web server that you want to monitor.

4 . Time Out

This parameter specifies a timeout period. During HTTP or HTTPS monitoring, the system calculates the response time of each HTTP or HTTPS packet that is sent. If the response time of a packet exceeds the specified timeout period, a health check times out. Valid values: 2 seconds, 3 seconds, 5 seconds, and 10 seconds.

5 . Continuous Failed Attempts

During HTTP or HTTPS monitoring, if several exceptions occur, an application service is deemed abnormal. This configuration ensures the accuracy of monitoring. The accuracy may be affected by some issues, such as the instantaneous network jitter. Valid values: 1 Times, 2 Times, and 3 Times.

  • 1 Times: An application service is deemed abnormal when the health check feature detects one alert.

  • 2 Times: An application service is deemed abnormal when the health check feature detects two alerts.

  • 3 Times: An application service is deemed abnormal when the health check feature detects three alerts.

6 . Failure Rate

During HTTP or HTTPS monitoring, this parameter specifies a rate of the number of failed monitoring nodes to the total number of monitoring nodes. If the failure rate exceeds the specified threshold, an application service is deemed abnormal. Valid values: 20%, 50%, 80%, and 100%.

7 . Return code is greater than

During HTTP or HTTPS monitoring, the system checks whether a web server functions as expected based on a status code that is returned from the web server. If a return code is greater than the specified threshold, an application service is deemed abnormal. Valid values:

  • 400: indicates a bad request. If an HTTP or HTTPS request includes invalid request parameters, a web server returns a status code that is greater than 400 if you set this parameter to 400. You must specify an absolute URL path in the URL Path parameter.

  • 500: indicates a server error. If some exceptions occur on a web server, the web server returns a status code that is greater than 500. Default value: 500.

8 . Host Configuration

During HTTP or HTTPS monitoring, this parameter specifies the Host field of an HTTP or HTTPS request header. The specified value indicates the HTTP website that you want to visit. By default, the value is the domain name that you specify in the global settings.

9 . URL Path

This parameter specifies a URL path when the system performs HTTP or HTTPS health checks. Default value: /.

10 . Enable SNI

After you turn on the switch, the system sends hostnames to a detection target during TSL negotiation.

11 . Monitoring Node

This parameter specifies the geographical locations of nodes on which you can perform HTTP or HTTPS monitoring. The following table describes the predefined monitoring nodes.

Node type

Geographical locations

BGP

Zhangjiakou, Qingdao, Hangzhou, Shanghai, Hohhot, Shenzhen, and Beijing.

Overseas

Hong Kong, Germany, Singapore, Silicon Valley, Australia, Malaysia, and Japan.

ISP

ChinaUnicomWuhan, ChinaUnicomDalian, ChinaUnicomNanjing, ChinaUnicomTianjin, ChinaTelecomQingdao, ChinaTelecomChangsha, ChinaTelecomXian, ChinaTelecomZhengzhou, ChinaMobileShenzhen, ChinaMobileDalian, and ChinaMobileNanjing.

Procedure

1 . Log on to the Alibaba Cloud DNS console.

2 . In the left-side navigation pane, click Global Traffic Manager. On the Global Traffic Manager page, click the required instance ID.

  • If you have not specified the required parameters for the instance, perform the steps that are provided in the Overview and Enable the health check feature topics of the Quick Start folder.

  • If you have specified the required parameters for the instance, click the Address Pool Configurations tab. On the Address Pool Configurations tab, turn on the Health Check switch and click Edit. You can modify the parameters of the HTTP or HTTPS health check feature based on the features of HTTP or HTTPS monitoring.

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