Asynchronous Single-process Event-driven Proxy Server

Asynchronous Single Process Event Driven Web Proxy is one of sub-subjects of "Multiple Function Server", a national project supported by "Electric Development Funds" of MII (Ministry of Information Industry). Currently the Internet is growing explosively,but the network bandwidth doesn't keep up with the increase of Information traffic and end users. All these make it an effective solution to implement the web proxy to alleviate network latency and traffic.This thesis, firstly, disusses and summarys web porxy's basic theory, working principle and cache technologies, then the HTTP protocol supporting cache coherence is emphasised as well. Through analysing and comparing different network server architectures and several event-dispatch mechanisms, It is realized that the Single Process Event Driven(SPED) architecure plus RT-Signal is adapt to implement efficient web proxy. At the same time, the solution of the critical network I/O issues related to SPED is analysed and figured out. Based on the previous research on web proxy, a SPED based proxy is designed. This server adopts real time signal mechanism, all network I/Os in this server work under the non-blocking mode. The non-blocking domain name resolution routine is implemented inside the server with the results cached. To speed up cache query, the proxy keeps cache's meta-data in memory that is managed via hash table. 5 big mmap files are allocated to improve the access of the cached objects litter than 8K. Special mapping function is also used to map meta-data to the cached objects in disk, aiming at decreasing directory depth and offering a balance distribution. This server uses the LRU-threshold cache replacement algorithm, a dynamic cache maintenance mechanism based on the fluctuation of request overload is used too. Finally,a basic prefetching routine is implementd in this web proxy.The test data proved that the design goal is reached and the proxy achieves high performance.