Web Proxy Server

Research & Implementation of Web Proxy is one sub-subject of "Network Dedicated Server", a "Electric Development Funds" supporting project from Ministry of Information Industry. Currently the Internet is growing explosively, but the network band-width doesn't come up with the increase of emerged Information and population using the Internet, all these make it an effective resolve to implement the web proxy to alleviate issues of network latency and traffic.In this thesis, firstly, it disusses and summarys web porxy's basic theory, working principle and cache technologies, the HTTP mechnism supporting cache coherence is researched as well. Through analysing and comparing different internal architectures of network server, It is emphasized that the Single Process Event Driven(SPED) architecure is adapt to implement effeciency web proxy, at the same time, the resolvement of critical network I/O issues related to SPED is analysied and figured out. Based on the previously research about web proxy, a SPED based web proxy is designed. This server adopts and implements the asynchronous event driven mechanism, all these network I/Os in the server work under the non-blocking style. The non-blocking domain name resolution mechanism is implemented in the internal of the server, the results of resolution is cached too. To speed up cache query, the web proxy keep cache's metadatas in-memory which is managed through hash table. Specially mapping function is used to map meta-data of cache to the cached file in disk, it aims to decrease directory depth and make these files distribute equaly. This server use a LRU ?threshold cache replacement algorithmm, a dynamic cache maintenance mechanism according to the request overload's variety is used to support the cache management too. At last, a simple prefetching technique is implementd in this web proxy.The test orkes approved that the design function is satisfied and the server achieves high performance.