Cloud Dynamic Software Update Mechanism Based On Intermediate Function

Cloud software systems always need to be updated to fix bugs, close security vulnerabilities and add features. However, traditional software updating approaches generally need to stop the running software, and then restart the software after finishing updating. Therefore, the software service will cause downtime and lost the service states. This is intolerant for the software which requires services to be available 24×7. However, the systems will be vulnerable if they do not apply patches in time. Thus, it is very important to offer a way to update running software system without shutting them down. Dynamic software update(DSU) is cheaper and less complex because it does not need extra hardware. However, existing DSU system have update safety problem and rollback problem.We present an Immediate and Safe Live Update System(ISLUS). ISLUS has three core subsystem. 1) Patch generator: the patch generator is used for building patch through constructing intermediate functions and function semantic mapping tables. 2) Update controller: the update controller can modify the running program to update it. 3) fault monitor: the fault monitor can get the update state continuously and restore the program from the wrong state.We evaluate ISLUS with vsftpd, sshd and Apache httpd. The results show that ISLUS can update the running software with downtime. During the process of dynamic update, the update time is less than 102 ms and the memory overhead is 0.15%-4.55%. The extra overhead of the software which updated is less than 5%. When the update error occurs, ISLUS can roll back the program to the state when it is in before the update begins less than 200 ms.