Class: RailsErrorDashboard::Services::CauseChainExtractor

Inherits:
Object
  • Object
show all
Defined in:
lib/rails_error_dashboard/services/cause_chain_extractor.rb

Overview

Pure algorithm: Extract the exception cause chain from an exception.

Ruby exceptions can have a ‘cause` (set automatically by `raise` inside a `rescue`). This service walks the chain recursively with a depth limit to prevent infinite loops from circular cause references.

Returns a JSON string of cause entries, or nil if no cause exists.

Examples:

CauseChainExtractor.call(exception)
# => '[{"class_name":"OriginalError","message":"connection refused","backtrace":["app/models/user.rb:10"]}]'

Constant Summary collapse

MAX_DEPTH = 
5
MAX_MESSAGE_LENGTH = 
1000
MAX_BACKTRACE_LINES = 
20

Class Method Summary collapse

Class Method Details

.call(exception) ⇒ String?

Returns JSON string of cause chain, or nil if no cause.

Parameters:

  • exception (Exception) —

    The exception to extract cause chain from

Returns:

  • (String, nil) —

    JSON string of cause chain, or nil if no cause



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# File 'lib/rails_error_dashboard/services/cause_chain_extractor.rb', line 23

def self.call(exception)
  return nil unless exception.respond_to?(:cause) && exception.cause

  chain = []
  current = exception.cause
  seen = Set.new
  depth = 0

  while current && depth < MAX_DEPTH
    # Guard against circular cause references
    break if seen.include?(current.object_id)
    seen.add(current.object_id)

    chain << {
      class_name: current.class.name,
      message: current.message&.to_s&.slice(0, MAX_MESSAGE_LENGTH),
      backtrace: truncate_backtrace(current.backtrace)
    }

    current = current.respond_to?(:cause) ? current.cause : nil
    depth += 1
  end

  chain.empty? ? nil : chain.to_json
rescue => e
  # SAFETY: Never let cause chain extraction break error logging
  RailsErrorDashboard::Logger.debug(
    "[RailsErrorDashboard] CauseChainExtractor failed: #{e.class} - #{e.message}"
  )
  nil
end