Implement Cache

[cooperlees]

We need a LRU key value store to put package Simple HTML into.

Proposed flows to support:

• On bandersnatch mirror update, generate main /simple/index.html
• On package access:
  • check cache for a version valid for current serial
  • if there pull from cache
  • Otherwise update package specific HTML + update cache
  • Serve HTML

Actually links will depend on storage used for blobs. Examples:

• filesystem
• S3
• Swift

I envision with S3 / Switch we'd use a CDN / service HTTP to redirect to for download of the blob (sdist or wheel).

[cooperlees]

https://github.com/cooperlees/banderfront/commit/0ed6d0236281da0520e9890b3f7375400aaf84f0 puts a POC up.

Next is to populate the /simple html root at startup and then get some routes to use the redis cache for the HTML.