Class: RailsErrorDashboard::Services::CacheAnalyzer

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

Overview

Pure algorithm: Analyze cache breadcrumbs at display time

Operates on already-captured breadcrumb data — zero runtime cost. Called at display time only. Similar pattern to NplusOneDetector.

Examples:

RailsErrorDashboard::Services::CacheAnalyzer.call(breadcrumbs)
# => { reads: 5, writes: 2, hits: 3, misses: 1, unknown: 1,
#      hit_rate: 75.0, total_duration_ms: 12.5,
#      slowest: { message: "cache read: users/1", duration_ms: 5.2 } }

Class Method Summary collapse

Class Method Details

.call(breadcrumbs) ⇒ Hash?

Returns Cache analysis summary, or nil if no cache breadcrumbs.

Parameters:

  • breadcrumbs (Array<Hash>) —

    Parsed breadcrumb array

Returns:

  • (Hash, nil) —

    Cache analysis summary, or nil if no cache breadcrumbs



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# File 'lib/rails_error_dashboard/services/cache_analyzer.rb', line 18

def self.call(breadcrumbs)
  return nil unless breadcrumbs.is_a?(Array)

  cache_crumbs = breadcrumbs.select { |c| c["c"] == "cache" }
  return nil if cache_crumbs.empty?

  reads = 0
  writes = 0
  hits = 0
  misses = 0
  unknown = 0
  total_duration = 0.0
  slowest = nil

  cache_crumbs.each do |crumb|
    message = crumb["m"].to_s
    duration = crumb["d"].to_f

    if message.start_with?("cache read:")
      reads += 1
      hit_status = crumb.dig("meta", "hit")
      if hit_status.nil?
        unknown += 1
      elsif hit_status == true || hit_status == "true"
        hits += 1
      else
        misses += 1
      end
    elsif message.start_with?("cache write:")
      writes += 1
    end

    total_duration += duration

    if slowest.nil? || duration > slowest[:duration_ms]
      slowest = { message: message, duration_ms: duration }
    end
  end

  # Only calculate hit_rate if we have read breadcrumbs with known hit status
  known_reads = hits + misses
  hit_rate = known_reads > 0 ? (hits.to_f / known_reads * 100).round(1) : nil

  {
    reads: reads,
    writes: writes,
    hits: hits,
    misses: misses,
    unknown: unknown,
    hit_rate: hit_rate,
    total_duration_ms: total_duration.round(1),
    slowest: slowest
  }
rescue => e
  nil
end