The pit of history can only be filled up as far as possible

Write it at the front

  Everyone will not be engaged in technology development for a short time . The company will definitely encounter the previous system , Due to personnel turnover , Ultimately, the maintenance responsibility falls on you . Such a system knows that there are many problems , But dare not change it without authorization ( It may cause more serious problems ). It's often a headache ！

Problem phenomenon

  At that time, the company's export gateway bandwidth alarm . therefore , Contact relevant personnel urgently , Although the business is at its peak , But it does not reach the point where the bandwidth of the exit gateway can be full . therefore , Emergency upgrade the exit bandwidth to the original 2 times . Although the situation eased at that time , But after a while, the bandwidth is still full . This problem remained unsolved until the end of the peak . Can only be tested repeatedly at night , Find and analyze the reason carefully .

Question why

  The final determination is the architecture of the system ： four layers SLB Forwarding problems . Because the fourth floor SLB Only responsible for IP And port forwarding , After the client establishes a connection with the server , All traffic of this connection is forwarded to the same server for processing . Establish connection table between client and server , The subsequent server responds to the client information according to the status of the connection table . However, connection timeouts occur from time to time , In the process of timeout reconnection , Because the timeout time of the system connection table of the virtual machine where the server is located is longer than that of the host connection table , As a result, the response data sent by the server to the client cannot find the corresponding connection table information in the host . that , This data packet becomes a data packet actively sent to the client at the host , And through the exit gateway , The bandwidth is obviously occupied .

terms of settlement

  Problems found , Analyze the reason . that , We must solve the problem . The problem is on the fourth floor SLB On , If it is changed to the seventh floor SLB Is it feasible . four layers SLB And the seventh floor SLB The difference between ：

• SLB, Load balancing service , four layers SLB Be similar to LVS; Seven layers SLB Be similar to Nginx.

• The four layer load is based on IP+Port; The seven layer load is based on URL

• Four layer load can only be analyzed IP Layer properties ; Seven layers of load will be recorded URL、 Browser categories 、 Language and other client attributes are more detailed .

Based on the above analysis , Seven layer load is more suitable than four layer load . It can be replaced with seven layers SLB, But I don't know why I chose the fourth floor at that time SLB, Led to today's accident .

summary

  In the company , All kinds of possible situations will happen . If predecessors can analyze more , Adopt seven layers SLB, There would be no accident today . But not so much if , I can only wish I could bury fewer holes for the people who receive the offer behind .