Memory Leak in ruby gem version 3.15.3 and above (including the latest 3.15.7)

[bruno-]

What version of protobuf and what language are you using?
Version: 3.15.7
Language: Ruby

What operating system (Linux, Windows, ...) and version?
Tried this on both Mac and Linux. The issue can be reproduced on both operating systems.

• Mac: Catalina 10.15.7 (19H2)
• Linux: Linux ubuntu2004.localdomain 5.4.0-65-generic Corrected code example in coded_stream.h #73-Ubuntu SMP Mon Jan 18 17:25:17 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

What runtime / compiler are you using (e.g., python version or gcc version)

Ruby 3.0.0.

Specific versions:

• Mac version: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
• Linux version: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-linux]

What did you do?

Use this gemfile:

# filename: gems.rb
source "https://rubygems.org"

gem "google-protobuf", "= 3.15.7"

Use this script:

# filename: test.rb
require "google/protobuf/well_known_types"

loop do
  Google::Protobuf::Value.new
end

• Install the google-protobuf gem with: bundle
• Run the script with: bundle exec ruby test.rb
• Monitor memory usage in htop in another terminal window.

What did you see?

I can observe that program memory usage grows really fast. I reaches 1Gb within a minute and continues to grow fast.

What did you expect to see

I expected the program's memory growth to stop at around 50Mb of memory use.

This happens (memory stops growing) with gem versions 3.15.2 and below.

Anything else we should know about your project / environment

• I originally reported this to grpc repo (link to issue GRPC Ruby Memory Leak grpc/grpc#25877) but then realized that is probably not the right place.
• This problem seems to be very similar to Memory Leak in ruby gem version 3.15.3 and above (including the latest 3.15.7) #8455 . There's a comment in that issue claiming the problem was fixed in latest ruby gem version 3.15.7. Unfortunately I was not able to confirm that: the problem described here does happen for me with 3.15.7.
• I tested various gem versions. This issue does not happen with google-protobuf gem versions 3.15.2 and below.
• I'm responsive, please ping me and I can provide additional help/clarification etc.

[bruno-]

Closing as this was fixed via #8461

Thank you for a quick fix 🙏