@amatsuda, during his RailsConf talk this past year, presented a
benchmark that showed `Time.zone.now` (an Active Support joint)
performing 24.97x slower than Ruby's `Time.now`. Rails master appears to
be a _bit_ faster than that, currently clocking in at 18.25x slower than
`Time.now`. Here's the exact benchmark data for that:
```
Warming up --------------------------------------
Time.now 127.923k i/100ms
Time.zone.now 10.275k i/100ms
Calculating -------------------------------------
Time.now 1.946M (± 5.9%) i/s - 9.722M in 5.010236s
Time.zone.now 106.625k (± 4.3%) i/s - 534.300k in 5.020343s
Comparison:
Time.now: 1946220.1 i/s
Time.zone.now: 106625.5 i/s - 18.25x slower
```
What if I told you we could make `Time.zone.now` _even_ faster? Well,
that's exactly what this patch accomplishes. When creating `ActiveSupport::TimeWithZone`
objects, we try to convert the provided time to be in a UTC format. All
this patch does is, in the method where we convert a provided time to
UTC, check if the provided time is already UTC, and is a `Time` object
and then return early if that is the case, This sidesteps having to continue on,
and create a new `Time` object from scratch. Here's the exact benchmark
data for my patch:
```
Warming up --------------------------------------
Time.now 124.136k i/100ms
Time.zone.now 26.260k i/100ms
Calculating -------------------------------------
Time.now 1.894M (± 6.4%) i/s - 9.434M in 5.000153s
Time.zone.now 301.654k (± 4.3%) i/s - 1.523M in 5.058328s
Comparison:
Time.now: 1893958.0 i/s
Time.zone.now: 301653.7 i/s - 6.28x slower
```
With this patch, we go from `Time.zone.now` being 18.25x slower than
`Time.now` to only being 6.28x slower than `Time.now`. I'd obviously love some
verification on this patch, since these numbers sound pretty interesting... :)
This is the benchmark-ips report I have been using while working on this:
```ruby
require 'benchmark/ips'
Time.zone = 'Eastern Time (US & Canada)'
Benchmark.ips do |x|
x.report('Time.now') {
Time.now
}
x.report('Time.zone.now') {
Time.zone.now
}
x.compare!
end
```
cc @amatsuda
cc performance folks @tenderlove and @schneems
In #25880 we tried to cache localtime to fix the performance
regression but that proved to be difficult due to the fact that
localtime/getlocal can take a utc_offset argument. We tried
caching based on the argument but since the argument can be nil
sometimes that meant that if the TZ environment variable changed
then the cached value for nil became invalid. By moving the
caching to DateAndTime#compatibility we don't have to worry about
arguments since it doesn't take any.
There is a possible edge condition where preserve_timezone is set
to false and the system timezone changes then it could result in
a cached value being incorrect but the only way to fix this would
be to remove all caching and live with the performance issue.
Turns out trying to cache on localtime with arguments is too hard
so we'll do it on DateAndTime::Compatibility#to_time instead.
This reverts commit 3132fa6b7d9585e04eb44b25b55d298391b040b5, reversing
changes made to 6949f8e5e7dc901d4e04ebab6c975afb33ca44c9.
Turns out trying to cache on localtime with arguments is too hard
so we'll do it on DateAndTime::Compatibility#to_time instead.
This reverts commit 9ce2d1b1a43fc4ef3db59849b7412d30583a4074, reversing
changes made to 53ede1aff2025d4391d0e05ba471fdaf3110a99c.
Before this patch, if you were to make a file edit in your Rails
application and you tried to load up the page, it would hang
indefinitely. The issue is that Active Record is trying to cleanup after
itself and clear all active connection, but Action Cable is still
holding onto a connection from the pool. To resolve this, we are now
shutting down the pubsub adapter before classes are reloaded, to avoid
this altogether (connection is being returned to the pool).
Credits to @skateman for discovering this bug. :)
this lets you pass ruby keywords to templates:
<%= render 'example', class: "cool" %>
<%= render 'example', "spaces are" => "a-ok" %>
<%= render 'example', Foo: "bar" %>
Previously you'd see confusing syntax errors like this:
SyntaxError (.../_example.html.erb:1: syntax error, unexpected '='
Now you can reference invalid identifiers through local_assigns.
If you try to use an invalid keyword (e.g. class) in your template, you
get a syntax error on the line where you use it.
Mostly, this is just to avoid EventMachine. But there's also an argument
to be made that we're better off using a different protocol library for
our test suite than the one we use to implement the server.
Zlib is used to generate the advisory lock since commit 2c2a8755460 .
Using the Migrator fails since then, when it is called without the rails context:
NameError: uninitialized constant ActiveRecord::Migrator::Zlib
This patch fixes the above error.
Previously memoization in `localtime` wasn't taking the `utc_offset`
parameter into account when returning a cached value. It now caches the
computed value depending on the `utc_offset` parameter, e.g:
Time.zone = "US/Eastern"
t = Time.zone.local(2016,5,2,11)
# => Mon, 02 May 2016 11:00:00 EDT -04:00
t.localtime(-7200)
# => 2016-05-02 13:00:00 -0200
t.localtime(-3600)
# => 2016-05-02 14:00:00 -0100
Callbacks are everywhere, so it's better if we can avoid making a mess
of the backtrace just because we've passed through a callback hook.
I'm making no effort to the before/after invocations: those only affect
backtraces while they're running. The calls that matter are the ones
that remain on the call stack after run_callbacks yields: around
callbacks, and internal book-keeping around the before/afters.
This was caused by 6d0d83a33f59d9415685852cf77818c41e2e2700. While the
bug it's trying to fix is handled if the association is loaded in an
after_(create|save) callback, it doesn't handle any cases that load the
association before the persistence takes place (validation, or before_*
filters). Instead of caring about the timing of persistence, we can just
ensure that we're not double adding the record instead.
The test from that commit actually broke, but it was not because the bug
has been re-introduced. It was because `Bulb` in our test suite is doing
funky things that look like STI but isn't STI, so equality comparison
didn't happen as the loaded model was of a different class.
Fixes#26661.
