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Try making puma metrics work by probing in puma workers #12238

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11 changes: 11 additions & 0 deletions config/puma.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -51,3 +51,14 @@
require_relative "../app/lib/credentials"

Credentials.load if ENV["DOPPLER_TOKEN"]

# https://docs.appsignal.com/ruby/integrations/puma.html#usage-with-preload_app
# Add this before_fork callback to stop the minutely probes in the Puma main process
before_fork do
Appsignal::Probes.stop
end

# Add this on_worker_boot callback to start the minutely probes in the Puma worker processes
on_worker_boot do
Appsignal::Probes.start
end
Comment on lines +57 to +64
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@sentry sentry bot Nov 25, 2025

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Bug: Incorrect AppSignal method names Appsignal::Probes.stop and Appsignal::Probes.start are used in Puma callbacks, leading to NoMethodError.
Severity: CRITICAL | Confidence: High

🔍 Detailed Analysis

The code in config/puma.rb calls incorrect method names on the AppSignal gem: Appsignal::Probes.stop and Appsignal::Probes.start. When Puma executes these callbacks in non-development environments (where preload_app! is enabled), it will attempt to call methods that do not exist on the AppSignal gem. This will raise a NoMethodError or NameError. In the before_fork callback, the Puma master process will crash before it can fork workers. In the on_worker_boot callback, each worker process will crash before it can accept requests, causing the application to fail to start in production.

💡 Suggested Fix

Replace Appsignal::Probes.stop with Appsignal.stop_probes and Appsignal::Probes.start with Appsignal.start_probes in config/puma.rb.

🤖 Prompt for AI Agent 
Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: config/puma.rb#L57-L64

Potential issue: The code in `config/puma.rb` calls incorrect method names on the
AppSignal gem: `Appsignal::Probes.stop` and `Appsignal::Probes.start`. When Puma
executes these callbacks in non-development environments (where `preload_app!` is
enabled), it will attempt to call methods that do not exist on the AppSignal gem. This
will raise a `NoMethodError` or `NameError`. In the `before_fork` callback, the Puma
master process will crash before it can fork workers. In the `on_worker_boot` callback,
each worker process will crash before it can accept requests, causing the application to
fail to start in production.

Did we get this right? 👍 / 👎 to inform future reviews.
Reference ID: 3466918