Vernier + profiling enabled causing silent crashes

[adam12]

Issue Description

With Vernier installed and configured as the profiler, there is a random segmentation fault encoutered inside Sentry, causing a 500 error user-facing, but no exception ever reported to Sentry. This can cause silent failures where there are no visible signs that the website is flakey other than failed requests.

I had this manifest on gemdocs.org.

From Gemfile.lock

    concurrent-ruby (1.3.5)
    sentry-rails (5.22.4)
      railties (>= 5.0)
      sentry-ruby (~> 5.22.4)
    sentry-ruby (5.22.4)
      bigdecimal
      concurrent-ruby (~> 1.0, >= 1.0.2)
    vernier (1.5.0)

Stacktrace

[9403b-a7c0-4727-b91c-e3518d748965] Started GET "/gems/datadog_api_client/2.23.0/DatadogAPIClient/V2/RUMApplicationCreateRequest.html" for 37.19.207.34 at 2025-02-23 04:27:54 +0000
/app/vendor/bundle/ruby/3.4.0/gems/vernier-1.5.0/lib/vernier/collector.rb:77: [BUG] Segmentation fault at 0x0000000000000000
ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +YJIT +PRISM [x86_64-linux]
-- Control frame information -----------------------------------------------

c:0036 p:---- s:0243 e:000242 CFUNC  :finish

c:0035 p:0003 s:0239 e:000238 METHOD /app/vendor/bundle/ruby/3.4.0/gems/vernier-1.5.0/lib/vernier/collector.rb:77

c:0034 p:0016 s:0231 e:000230 METHOD /app/vendor/bundle/ruby/3.4.0/gems/vernier-1.5.0/lib/vernier.rb:56

c:0033 p:0018 s:0226 e:000225 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/vernier/profiler.rb:76

c:0032 p:0043 s:0221 e:000220 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/transaction.rb:260

c:0031 p:0017 s:0211 e:000210 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/rack/capture_exceptions.rb:83

c:0030 p:0102 s:0205 e:000204 BLOCK  /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/rack/capture_exceptions.rb:43

c:0029 p:0020 s:0198 e:000197 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/hub.rb:269

c:0028 p:0017 s:0193 e:000192 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry-ruby.rb:420

c:0027 p:0006 s:0188 e:000187 BLOCK  /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/rack/capture_exceptions.rb:21

c:0026 p:0009 s:0184 e:000183 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/hub.rb:59

c:0025 p:0017 s:0179 e:000178 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry-ruby.rb:400

c:0024 p:0024 s:0174 e:000173 METHOD /app/vendor/bundle/ruby/3.4.0/gems/sentry-ruby-5.22.4/lib/sentry/rack/capture_exceptions.rb:20

c:0023 p:0007 s:0169 e:000168 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/show_exceptions.rb:32

c:0022 p:0047 s:0160 E:001a38 METHOD /app/vendor/bundle/ruby/3.4.0/gems/railties-8.0.1/lib/rails/rack/logger.rb:41

c:0021 p:0048 s:0147 e:000146 METHOD /app/vendor/bundle/ruby/3.4.0/gems/railties-8.0.1/lib/rails/rack/logger.rb:29

c:0020 p:0028 s:0141 e:000140 METHOD /app/vendor/bundle/ruby/3.4.0/gems/railties-8.0.1/lib/rails/rack/silence_request.rb:28

c:0019 p:0034 s:0136 e:000135 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/remote_ip.rb:96

c:0018 p:0030 s:0130 e:000129 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/request_id.rb:34

c:0017 p:0057 s:0124 e:000123 METHOD /app/vendor/bundle/ruby/3.4.0/gems/rack-3.1.9/lib/rack/method_override.rb:28

c:0016 p:0013 s:0118 e:000117 METHOD /app/vendor/bundle/ruby/3.4.0/gems/rack-3.1.9/lib/rack/runtime.rb:24

c:0015 p:0019 s:0108 e:000107 METHOD /app/vendor/bundle/ruby/3.4.0/gems/activesupport-8.0.1/lib/active_support/cache/strategy/local_cache_middleware.rb:29

c:0014 p:0016 s:0101 e:000100 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/executor.rb:16

c:0013 p:0018 s:0092 e:000091 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/static.rb:27

c:0012 p:0007 s:0087 e:000086 METHOD /app/vendor/bundle/ruby/3.4.0/gems/rack-3.1.9/lib/rack/sendfile.rb:114

c:0011 p:0021 s:0074 e:000073 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/ssl.rb:92

c:0010 p:0043 s:0068 e:000067 METHOD /app/vendor/bundle/ruby/3.4.0/gems/actionpack-8.0.1/lib/action_dispatch/middleware/assume_ssl.rb:24

c:0009 p:0016 s:0063 e:000062 METHOD /app/vendor/bundle/ruby/3.4.0/gems/railties-8.0.1/lib/rails/engine.rb:535

c:0008 p:0017 s:0057 e:000056 METHOD /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/configuration.rb:279

c:0007 p:0007 s:0052 e:000051 BLOCK  /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/request.rb:99

c:0006 p:0015 s:0049 e:000048 METHOD /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/thread_pool.rb:390

c:0005 p:0353 s:0044 e:000043 METHOD /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/request.rb:98

c:0004 p:0093 s:0029 e:000028 METHOD /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/server.rb:472

c:0003 p:0005 s:0018 e:000017 BLOCK  /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/server.rb:254

c:0002 p:0071 s:0014 e:000013 BLOCK  /app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/thread_pool.rb:167 [FINISH]

c:0001 p:---- s:0003 e:000002 DUMMY  [FINISH]
-- Ruby level backtrace information ----------------------------------------

/app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/thread_pool.rb:167:in 'block in spawn_thread'

/app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/server.rb:254:in 'block in run'

/app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/server.rb:472:in 'process_client'

/app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/request.rb:98:in 'handle_request'

/app/vendor/bundle/ruby/3.4.0/gems/puma-6.6.0/lib/puma/thread_pool.rb:390:in 'with_force_shutdown'

/pre>

Reproduction Steps

Unknown.

Expected Behavior

Not to crash.

Actual Behavior

Crashes silently.

Ruby Version

3.4.1

SDK Version

5.22.4

Integration and Its Version

Rails (8.0.1)

Sentry Config

Sentry.init do |config|
  config.dsn = ENV["SENTRY_DSN"]

  # get breadcrumbs from logs
  config.breadcrumbs_logger = [:active_support_logger, :http_logger]

  # enable profiling
  # this is relative to traces_sample_rate
  config.profiles_sample_rate = 1.0

  # Use Vernier for profiling
  config.profiler_class = Sentry::Vernier::Profiler

  config.traces_sampler = lambda do |sampling_context|
    # if this is the continuation of a trace, just use that decision (rate controlled by the caller)
    unless sampling_context[:parent_sampled].nil?
      next sampling_context[:parent_sampled]
    end

    0.5
  end
end

[solnic]

Thanks for reporting this Adam 🙇🏻 I'll be looking into this today, but since this is coming from Vernier I'm afraid I won't be able to fix it quickly. One thing I need to check is why segfaults are not being reported for you by Sentry.

[sl0thentr0py]

we are simply a library that runs within ruby, segfaults crash ruby entirely so there is no way we could catch those. That would require an agent living parallel to the ruby process.