Thumbnail cache

[mugglmenzel]

Embed.ly shows very high latency which leads to a bad user experience :( for example, bg images and thumbnails are loaded after the whole page is already loaded leaving image overlays with buttons as weird constructs. bg images appear very late on a page surprising users upon appearance.

the thumbnail cache works the following:

• image requests against endpoint of thumbnail cache, such as journwe.com/thumbnail?width=1200&height=800&image=journwe-s3-bucket-for-adventure-images/image-id.jpg (or later on thumbs.journwe.com cluster)
• server checks for file in thumbnail cache bucket on s3 (construct url from parameters) -- if not available: download from emebed.ly with parameters -- if available: return redirect to s3/cdn file of cached thumbnail

file sprawl resp. cache size:

• set s3 file lifetime to max. 7 days or run akka to clean old files
• deleted files will be fetched from embed.ly anyway

[mugglmenzel]

@markusklems some whiteboard time for the backend group (markus + me) :wink: