I wrote a utility that helps find areas where you could optimize your program using a frozen string instead of a string literal, it's called [let_it_go](https://github.com/schneems/let_it_go). After going through the output and adding `.freeze` I was able to eliminate the creation of 1,114 string objects on EVERY request to [codetriage](codetriage.com). How does this impact execution?
To look at memory:
```ruby
require 'get_process_mem'
mem = GetProcessMem.new
GC.start
GC.disable
1_114.times { " " }
before = mem.mb
after = mem.mb
GC.enable
puts "Diff: #{after - before} mb"
```
Creating 1,114 string objects results in `Diff: 0.03125 mb` of RAM allocated on every request. Or 1mb every 32 requests.
To look at raw speed:
```ruby
require 'benchmark/ips'
number_of_objects_reduced = 1_114
Benchmark.ips do |x|
x.report("freeze") { number_of_objects_reduced.times { " ".freeze } }
x.report("no-freeze") { number_of_objects_reduced.times { " " } }
end
```
We get the results
```
Calculating -------------------------------------
freeze 1.428k i/100ms
no-freeze 609.000 i/100ms
-------------------------------------------------
freeze 14.363k (± 8.5%) i/s - 71.400k
no-freeze 6.084k (± 8.1%) i/s - 30.450k
```
Now we can do some maths:
```ruby
ips = 6_226k # iterations / 1 second
call_time_before = 1.0 / ips # seconds per iteration
ips = 15_254 # iterations / 1 second
call_time_after = 1.0 / ips # seconds per iteration
diff = call_time_before - call_time_after
number_of_objects_reduced * diff * 100
# => 0.4530373333993266 miliseconds saved per request
```
So we're shaving off 1 second of execution time for every 220 requests.
Is this going to be an insane speed boost to any Rails app: nope. Should we merge it: yep.
p.s. If you know of a method call that doesn't modify a string input such as [String#gsub](b0e2da69f0/lib/let_it_go/core_ext/string.rb (L37)) please [give me a pull request to the appropriate file](b0e2da69f0/lib/let_it_go/core_ext/string.rb (L37)), or open an issue in LetItGo so we can track and freeze more strings.
Keep those strings Frozen
Because URI paths may contain non US-ASCII characters we need to force
the encoding of any unescaped URIs to UTF-8 if they are US-ASCII.
This essentially replicates the functionality of the monkey patch to
URI.parser.unescape in active_support/core_ext/uri.rb.
Fixes#16104.
1. Escape '%' characters in URLs - only unescaped data
should be passed to URL helpers
2. Add an `escape_segment` helper to `Router::Utils`
that escapes '/' characters
3. Use `escape_segment` rather than `escape_fragment`
in optimized URL generation
4. Use `escape_segment` rather than `escape_path`
in URL generation
For point 4 there are two exceptions. Firstly, when a route uses wildcard
segments (e.g. *foo) then we use `escape_path` as the value may contain '/'
characters. This means that wildcard routes can't be optimized. Secondly,
if a `:controller` segment is used in the path then this uses `escape_path`
as the controller may be namespaced.
Fixes#14629, #14636 and #14070.
The URI::Parser#escape method is a general use method that has to deal
with a variety of input however our use of it is limited in scope so
we can increase the performance by implementing our specific needs
within ActionDispatch::Journey::Router::Utils directly.
If there is no encoding required then there is no change in performance
or number of objects allocated, but for each character that needs to be
encoded we save five object allocations and gain a performance boost.
The performance boost seen varies from 20% when there is one character
to over 50% when encoding ten characters.
Makes it clear that anything passed with the helper must not be percent encoded.
Fixes previous behavior which tricks people into believing passing
non-percent-encoded will generate a proper percent-encoded path while in
reality it doesn't ('%' isn't escaped).
The intention is nice but the heuristic is broken.
Move the Journey code underneath the ActionDispatch namespace so
that we don't pollute the global namespace with names that may
be used for models.
Fixesrails/journey#49.
