After Weblogic is started, you cannot access the console or applications.

Feedback from the implementer yesterday: After Weblogic is started, you cannot enter the console. IE displays a blank page and does not even have a logon interface!

I personally remotely log on to the server to access the server. In this case, all the Weblogic-related files are displayed. It is depressing that the problem of no error is the most difficult to solve. The service cannot be restarted because the system is running. After thinking about it, I thought I had to go online to find relevant information. Later I found the following article:

After Weblogic is started, you cannot access the console or applications.

This is an abnormal and weird problem. It is also the most strange and difficult problem to solve. During the trial run, our system occasionally fails to log on to the application system. At the same time, webLogic console cannot be logged on either. However, check the process in the operating system, WebLogic process is still running, and the background output of the application and WebLogic log file output have no error information.

At the beginning, a system problem occurs. We can always solve the problem by restarting the system. Occasionally, the problem can be solved after two restarts. I also contacted Bea engineers who provided various solutions. For example, when a problem occurs, I used Telnet IP port to check whether the application can be connected, for example, you can use the kill-3 method to print the dump information and send it to them to check the cause. In the end, the problem still fails to be solved. At most one time, our application went down for 2 hours.

Later on, the system never encountered this problem. But one day, the problem suddenly appeared again, and this time it was a storm, and later it basically reached a whole day of system access. We use the Weblogic domain and server reconstruction method to modify the login port method. Every time we stick to it for a while, the problem will occur again. Even more seriously, after Weblogic is restarted, the system is almost inaccessible immediately. I even thought about whether WebLogic software is a problem. I almost wanted to use Websphere to replace it.

Later, we used VPN to let Bea engineers log on to the system to check the cause, but their 800 engineers did not find the cause, and I was so depressed. Bea's Guangzhou presales engineer found that there were about 70 connections in syn_rcvd status when checking the system status. This is related to malicious DoS attacks. (Http://www-900.ibm.com/developerWorks/cn/security/se-ddos/index.shtml)

After testing, this is the cause. Netstat-an | grep SYN | the number of wc-l displayed each time must be greater than 70, which is basically inaccessible to the system. Later, we solved this problem through two firewalls (one controlling access outside the Intranet and the other controlling access within the Intranet ).

This problem plagued me for a long time and tested various methods. This article mainly describes two problems. First, the network and virus issues must be taken into account when troubleshooting system faults. Second, we did not disconnect all network connections from the server when eliminating system problems. If this method is used, problems may be detected earlier. Third: it is the most difficult to find such problems without any error prompts. Please be careful.

The above bold Chinese characters are excerpted from Java free man

After reading this, I thought it was a lot of a mess. If so, it would be okay to restart the system. However, we need to enhance the server security settings in the future.

Sure enough, after the system is restarted at night, everything is OK, but I don't know if it will happen again in the future.