Ashd A Sane HTTP Daemon
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daemon HTTP http server Sane HTTP daemon

Ashd Description

A Sane HTTP Daemon Ashd is a modular HTTP server software based on a multi-program architecture. Whereas most other HTTP servers are monolithic programs with, perhaps, loadable modules, Ashd is composed of several different programs, each of which handles requests in different ways, passing requests to each other over a simple protocol (not unlike Unix pipelines). The design of Ashd brings it a number of nice properties, the following being the most noteworthy ones.Sanity of design The separation of concerns between different, independent programs is an example of standard Unix philosophy – each program does one thing only, but does it well (I hope). The clean delineation of functions allows each program to be very small and simple – currently, each of the programs in the collection (including even the core HTTP parser program, htparser, as long as one does not count its, quite optional, SSL implementation) is implemented in less than 1,000 lines of C code (and most are considerably smaller than that), allowing them to be easily studied and understood.Security Since each program runs in a process of its own, it can be assigned proper permissions. Most noteworthy of all, the userplex program ensures that serving of user home directories (/~user/ URLs, if you will) only happens by code that is actually logged in as the user in question; and the htparser program, being the only program which speaks directly with the clients, can run perfectly well as a non-user (like nobody) and be chroot'ed into an empty directory.Configuration sanity Again, since each program only handles a simple task, its configuration can be made quite simple. There is no need for the dirplex program, which handles only service from physical directories, to care about virtual directories, virtual hosts, HTTP protocol parameters or authentication; just as there is no need for the patplex pattern matcher to know about file types or directory hierarchies. Each program's configuration file format can be kept as simple as possible, and most programs are configured simply with command-line options.Persistence Though Ashd is a multi-process program, it is not in the same sense as e.g. Apache. Each request handler continues to run indefinitely and does not spawn multiple copies of itself, meaning that all process state persists between requests – session data can be kept in memory, connections to back-end services can be kept open, and so on.

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