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

Traffic Forwarding

  • 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 receive response message from “a-demo-static-1.idc1”.

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