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2. Shared Memory Management

All web application developers grapple with the question of how to maintain state between page views. Many paradigms exist for the passing of small name value pairs from page to page via the query string or HTML Form submissions. But often times one must maintain complex data over multiple page views, such as the contents of a shopping cart, or changes to a Personal Homepage. The best way to maintain such data is in objects.

Mantaining objects in memory between page views is problematic for Apache modules on Unix since each page view may be handled by a different process. Processes, unlike threads, each have their own memory and are prohibited from reading from or writing to each others memory.

Moto solves this problem by providing developers with a shared memory manager. At Apache startup the parent Apache process initializes a shared memory segment and gives each child process rights to it as they are spawned. APIs are provided for malloc, calloc, realloc, and free replacement functions which work against this shared memory segment. All of the included codex libraries are compiled against these APIs.

This memory manager provides a number of other important features including:

  1. Thread (process) safety
  2. Numerous debugging and diagnostic functions
  3. An included Garbage Collector

It is open source and may be used on other open source projects. Check out the code in the moto distribution in moto/src/codex/sharedmem.c