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Function overview

Last Updated: Sep 14, 2018

Alibaba Cloud GTM provides the following functions:

Function 1: address pool management

You can group different IP addresses of the same application service into different address pools for management. Put IP addresses of different regions in different address pools, which greatly facilitates health check configuration and fault isolation realization for the application service.

You can set different working modes for different IP addresses in an address pool:

  • Smart Return: the default working mode. In this mode, GTM decides whether to add this IP address to the IP address list responded to a DNS request based on whether the health check result is normal or abnormal.
  • Always Online: In this mode, health check is not performed for the IP address and GTM regards that the IP address is always normal. To provide services in an unstable network environment, you can set the IP address to work in Always Online mode.
  • Always Offline: In this mode, health check is not performed for the IP address and GTM regards that the IP address is always abnormal and removes the IP address from the IP address list responded to the DNS request. To upgrade a cluster, you need to set the IP address of this cluster to work in Always Offline mode.

You can set a load balancing policy for the list of IP addresses in an address pool during response to a DNS request.

  • Load balancing: All the IP addresses are returned at a random order each time. The application selects the first IP address by default and the access traffic is evenly allocated.
  • Weighted round robin: In the DNS request response, IP addresses are returned according to their preset weights. If the application service can be accessed nationwide, the access traffic can be allocated by weight.

Function 2: health check

You can configure unified health check for IP addresses in an address pool to monitor the availability of the application service in real time.

  • Health check can be performed based on the ping, TCP, or HTTP(S) protocol.
  • Monitoring nodes for health check
    • Nodes inside China:
    • Nodes outside China:
  • Health check cycle: Each monitoring node executes the health check task independently. The interval between two health check tasks at a monitoring node is one minute.

Function 3: access policy

You can set an access policy to enable users in different regions to access different address pools, accelerating accesses of users in different regions.

  • Acceleration regions:
    • Carriers inside China: China Unicom, China Telecom, China Mobile, and Dr. Peng.
    • Regions inside China: Northeast, Northwest, Southwest, China North, China East, Central China, and China South.
    • Regions outside China: Asia (China excluded), Europe, Africa, North America, South America, and Oceania.

Function 4: DNS Failover

  • GTM can dynamically adjust the list of IP addresses in an address pool based on the health check result of the IP addresses. When an IP address has a fault, GTM deletes this IP address from the list responded to the DNS request. When the faulty IP address is restored to normal, GTM re-adds the IP address to the list.
  • GTM allows you to set a minimum number of available IP addresses in an address pool. When the number of healthy IP addresses in the address pool is less than the minimum number of available IP addresses, the system deems that the whole address pool is unavailable.
  • When you access a DNS address pool corresponding to a domain name, you can configure a default address pool for access in normal case, and a backup address pool Failover address pool when the default address pool is abnormal. In this case, when the default address pool has a fault, users can access the application service through the backup address pool, ensuring the business continuity.