Previously, we would initialize an ImageOptim object each time we resize.
This object init is mega expensive (170ms on a VERY fast machine):
```
[1] pry(main)> Benchmark.measure { FileHelper.image_optim }
=> #<Benchmark::Tms:0x00007f55440c1de0
@cstime=0.055742,
@cutime=0.141031,
@label="",
@real=0.17165619300794788,
@stime=0.0002750000000000252,
@total=0.19890400000000008,
@utime=0.0018560000000000798>
```
This happens cause during init it hunts for all the right binaries and sets
up internals.
We now memoize this object to avoid a huge amount of pointless work.
Historically due to https://meta.discourse.org/t/why-is-discourse-so-slow-on-android/8823
we decreased page sizes of both home page and topic page on android by half.
This was done on the server side and as a side effect and caused page sizes on android
to mismatch between Android and non Android.
Unfortunately about a year ago googlebot started pretending it is Android,
this cause Google to start indexing pages as what android would see. So
it saw double the amount of pages in the index as what exists on desktop.
This in turn caused double the amount of indexing work and a large amount
of broken links on long topics.
This fix removes all special behavior which is no longer needed due to
other performance work in Discourse including raw handlebars on home page
and virtual dom on topic pages.
I tested we do not need this on Blu Advance 5.0 it has 1.3 GHZ mediatec mt6580
This phone retails for around $50 USD.
If we decide long term that we want any hacks like this we will shift them
to the client side. It can just hold data in memory without rendering.
This ensures that the hostname rails uses for various helpers always matches
the Discourse hostname
# Conflicts:
# config/application.rb
# spec/requests/application_controller_spec.rb
If we detect redis is in readonly we can not correctly get a mutex
raise an exception to notify caller
When getting optimized images avoid the distributed mutex unless
for some reason it is the first call and we need to generate a thumb
In redis readonly no thumbnails will be generated
previously admin got a free pass and could set theme via cookie to anything
including themes that are not selectable
this refactor ensures that only "preview" gets a free pass, all the rest
goes through the same pipeline
