SCons' internal CacheDir class can be extended to support customization around the details of caching behaviors, for example using compressed cache files, encrypted cache files, gathering statistics and data, or many other aspects.

To create your own custom cache class, your custom class must be a subclass of the SCons.CacheDir.CacheDir class. You can then pass your custom class to the CacheDir method or set the construction variable $CACHEDIR_CLASS to the class before configuring the cache in that environment. SCons will internally invoke and use your custom class when performing cache operations. The below example shows a simple use case of overriding the copy_from_cache method to record the total number of bytes pulled from the cache.

import SCons
import os

class CustomCacheDir(SCons.CacheDir.CacheDir):
    total_retrieved = 0

    @classmethod
    def copy_from_cache(cls, env, src, dst):
        # record total bytes pulled from cache
        cls.total_retrieved += os.stat(src).st_size
        super().copy_from_cache(env, src, dst)

env = Environment()
env.CacheDir('scons-cache', CustomCacheDir)
# ...