Concepts

• Product：

  • The product equals "tenant" in BFE, which has its own configuration, such as routing policy, permission, etc.
  • Field "host" in HTTP header is used to identify product that the incoming message belongs to.

• Cluster：

  • Cluster means a set of backend servers which provide same functionality and process similar task.
  • Usually，cluster span multiple IDC/region in scope。

• Sub Cluster：

  • A cluster may be composed of multiple sub clusters conceptually。
  • Usally, backend servers within one IDC/region is defiend as a sub cluster.

• Instance：

  • Instance is backend server. A sub cluster would contain multiple instances.
  • To BFE，each backend instance expose IP address + port to accept request.

Typical message routing flow

• Step1-2：DNS query

  • request host name：demo.example.com
  • get IP address 6.6.6.6（example）

• Step3：IP diagram is routed to POP of IDC1，and processed by layer 4 load balancer L4LB.

• Step4：L4LB forward diagram to BFE

• Step5：BFE receive HTTP request, identify which product the request belongs to:

  • BFE uses field "host" in HTTP header to decide product.
  • In this scenario, assume demo.example.com belongs to product "demo".

• Step6：Identify a cluster of product "demo", which would handle this message.

  • Based on configured distribution rule of product "demo", identify cluster "demo-static" in this product to handle the message .

• Step7：Identify a sub cluster within "demo-static"

  • Based on routing rule in "demo-static", identify sub cluster "demo-static.idc1" to handle this message.

• Step8：Identify instance

  • based on configured load balancing policy, identify instance as "a-demo-static-1.idc1".

• Step9：request is sent to instance "a-demo-static-1.idc1".

• Step10：BFE recieve response message from "a-demo-static-1.idc1".

• Step11-12：BFE send back reponse to client, via L4LB.