Not sure if this is the Elixir-y way to do this, but seems more logical
than hardcoding values such as redis connection.
Also went through and improved how string formatting was performed
throughout the app. Rather than "combining" <> "strings" this way, I'm
now just doing "#${variable}#{formatting}", which looks a lot cleaner.
The update script now writes the available instances to a
.update-results* file (where previous runs have "-prev" appended to the
file name). This helps to see how instance availability changes between
runs of the script when debugging overall functionality of the app.
Once a list of available URLs has been determined for a particular
service, the list is written as "service -> [list of instances]" to a
local redis connection. These can then be used in the greater routing
logic to pick a random instance from the list, or use a fallback
instance if none are determined to be available.
My initial thought for this: create a simple redis db for storing key
value pairs of instance -> list of live instances for each privacy front
end (libreddit, bibliogram, etc). A script executed on a certain
schedule would (in the background) check each instance to make sure it
isn't down or unreasonably slow. If the instance is available, add it to
a list of available instances in the db.
When a user navigates to the revolver url (something like
<url>/<service>/<...>), the app would pick a random value from the list
returned by redis.get('<service>') and forward the user to that
instance.
As a side note, this could instead load the instances json from a remote
source (like github or something) so that changes to instances don't
need to involve a redeploy of the entire app.
