Sentry::Scope#set_transaction_name leaks memory

[c960657]

Issue Description

The method name Sentry::Scope#set_transaction_name suggests that it is a simple setter, but in fact it appends the specified name to an array. AFAICT this array is never popped/truncated, so if #set_transaction_name is called e.g. in an event loop, the array will grow unlimited.

I know that Sentry.with_scope is often a better solution inside a loop, but this is not always a feasible solution, e.g. if exceptions are rescued outside the loop.

Reproduction Steps

while true do
  Sentry.configure_scope do |scope|
    scope.set_transaction_name('foo')
    p scope.transaction_names.size
  end
end

Expected Behavior

The transaction names should not accumulate.

Actual Behavior

An ever increasing number is output, proving that the Sentry::Scope#transaction_names array keeps growing. Eventually a NoMemoryError is raised.

Ruby Version

3.2.3

SDK Version

5.15.0

Integration and Its Version

No response

Sentry Config

No response

[sl0thentr0py]

thx for the report, this whole transaction name stuff is a bit of mess at the moment. In general, there's no reason it needs to be an array, we just care about the last one anyway.

[henrikbjorn]

@sl0thentr0py This issue seem to impact different part of a rails system. For example ActionCable would be impacted via https://github.com/getsentry/sentry-ruby/blob/master/sentry-rails/lib/sentry/rails/action_cable.rb#L19

Also it seems that the method now also pushes to another array which makes doubles the amount of memory persisted. https://github.com/getsentry/sentry-ruby/blob/master/sentry-ruby/lib/sentry/scope.rb#L235

What are the next steps?