Get ObjectSpace heap dump via signal

heap_dump.rb

# frozen_string_literal: true

# Heap Dump Signal Trap
#
# Send CONT signal to the process to trigger a heap dump.
#
# Usage:
#   kill -CONT <pid>
#
# Output:
#   - First signal: Starts object allocation tracking (no dump created)
#   - Subsequent signals: Creates /tmp/heap-1.json, /tmp/heap-2.json, etc.
#   - Logs: /tmp/heapdump.log
#
# Analysis tools:
#   - https://github.com/Shopify/heap-profiler
#   - https://github.com/zombocom/heapy
#   - https://github.com/jhawthorn/sheap
#   - https://github.com/oxidize-rb/reap

heap_dump_counter = -1

Signal.trap("CONT") do
  Thread.new do
    heap_dump_counter += 1

    # Check if this is the first signal
    if heap_dump_counter.zero?
      require 'objspace'
      ObjectSpace.trace_object_allocations_start
      File.open("/tmp/heapdump.log", "a") do |f|
        f.puts "[#{Time.now.iso8601}] [PID:#{Process.pid}] ObjectSpace.trace_object_allocations_start"
      end
      next
    end

    filename = "/tmp/heap-#{heap_dump_counter}.json"
    File.open("/tmp/heapdump.log", "a") do |f|
      f.puts "[#{Time.now.iso8601}] [PID:#{Process.pid}] Creating heap dump: #{filename}"
    end

    # Trigger garbage collection before dump for cleaner results
    GC.start

    File.open(filename, "w") do |file|
      ObjectSpace.dump_all(output: file)
    end

    file_size = File.size(filename) / 1024 / 1024 # Size in MB
    File.open("/tmp/heapdump.log", "a") { |f|
      f.puts "[#{Time.now.iso8601}] [PID:#{Process.pid}] Heap dump created: #{filename} (#{file_size} MB)"
    }
  rescue => ex
    File.open("/tmp/heapdump.log", "a") { |f|
      f.puts "[#{Time.now.iso8601}] [PID:#{Process.pid}] ERROR: #{ex.message}\n#{ex.backtrace.join("\n")}"
    }
  end
end