Add fiber churn example.

Author: samuel-williams-shopify

examples/dead_fibers.rb

@@ -0,0 +1,201 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require_relative "../config/environment"
+require_relative "../lib/memory/profiler"
+
+puts "Memory Profiler - Dead Fiber Detection"
+puts "=" * 80
+puts "Configuration:"
+puts "  - Total fiber allocations: 100,000"
+puts "  - Churn ratio: 10:1 (10 dead for every 1 retained)"
+puts "  - Expected retained: ~9,091 fibers"
+puts "  - Object type: Fiber"
+puts "=" * 80
+puts
+
+TOTAL_FIBERS = 100_000
+CHURN_RATIO = 10  # 10 dead : 1 retained
+RETAINED_COUNT = TOTAL_FIBERS / (CHURN_RATIO + 1)
+CHURNED_COUNT = TOTAL_FIBERS - RETAINED_COUNT
+
+puts "Starting capture..."
+capture = Memory::Profiler::Capture.new
+capture.track(Fiber)
+capture.start
+
+puts "Phase 1: Creating #{RETAINED_COUNT} retained (alive) fibers..."
+retained_fibers = []
+
+start_time = Time.now
+
+# Create retained fibers that stay alive
+RETAINED_COUNT.times do |i|
+	fiber = Fiber.new do
+		# Keep fiber alive by yielding
+		Fiber.yield i
+		# This fiber will stay alive because we resume it
+		Fiber.yield i * 2
+	end
+	# Resume once to start it
+	fiber.resume
+	retained_fibers << fiber
+	
+	if (i + 1) % 10_000 == 0
+		elapsed = Time.now - start_time
+		rate = (i + 1) / elapsed
+		puts "  Created #{i + 1} retained fibers (#{rate.round(0)} fibers/sec)"
+	end
+end
+
+puts "\nPhase 2: Creating #{CHURNED_COUNT} churned (dead) fibers (with GC)..."
+puts "  (These will be created, finish execution, and become dead)"
+puts "  (10% will be retained for counting purposes)"
+
+churn_start = Time.now
+churned_so_far = 0
+gc_count = 0
+dead_fibers_retained = []  # Retain 10% of dead fibers for counting
+
+# Create churned fibers in batches with periodic GC
+while churned_so_far < CHURNED_COUNT
+	# Create a batch of temporary fibers that will finish and become dead
+	batch_size = 10_000
+	batch_size.times do |i|
+		# Create a fiber that finishes immediately (becomes dead)
+		fiber = Fiber.new do
+			# Fiber finishes here - becomes dead
+			churned_so_far
+		end
+		# Resume it once to make it finish
+		fiber.resume
+		# Fiber is now dead (finished execution)
+		
+		# Retain 10% of dead fibers for counting
+		if churned_so_far % 10 == 0
+			dead_fibers_retained << fiber
+		end
+		# Rest are not retained - let them be GC'd
+		
+		churned_so_far += 1
+		break if churned_so_far >= CHURNED_COUNT
+	end
+	
+	# Periodic GC to clean up dead fibers and test deletion performance
+	if churned_so_far % 50_000 == 0
+		GC.start
+		gc_count += 1
+		elapsed = Time.now - churn_start
+		rate = churned_so_far / elapsed
+		
+		# Use each_object to count alive vs dead fibers
+		alive_count = 0
+		dead_count = 0
+		total_tracked = 0
+		
+		capture.each_object(Fiber) do |fiber, allocations|
+			total_tracked += 1
+			# Check if fiber is dead using fiber.alive?
+			if fiber.alive?
+				alive_count += 1
+			else
+				dead_count += 1
+			end
+		end
+		
+		puts "  Churned: #{churned_so_far} | Tracked: #{total_tracked} | Alive: #{alive_count} | Dead: #{dead_count} (via each_object) | GCs: #{gc_count} | Rate: #{rate.round(0)} fibers/sec"
+	end
+end
+
+# Final GC to clean up any remaining dead fibers
+puts "\nPhase 3: Final cleanup..."
+3.times{GC.start}
+
+end_time = Time.now
+total_time = end_time - start_time
+
+puts "\n" + "=" * 80
+puts "RESULTS"
+puts "=" * 80
+
+# Use each_object to iterate over all tracked fibers and count dead ones
+# This demonstrates that each_object can access both alive and dead fibers
+alive_fibers = []
+dead_fibers = []
+total_tracked = 0
+
+puts "Counting fibers using capture.each_object(Fiber)..."
+capture.each_object(Fiber) do |fiber, allocations|
+	total_tracked += 1
+	if fiber.alive?
+		alive_fibers << fiber
+	else
+		dead_fibers << fiber
+	end
+end
+
+fiber_count = capture.retained_count_of(Fiber)
+
+puts "Fiber Statistics (from each_object iteration):"
+puts "  Total tracked:    #{total_tracked.to_s.rjust(8)}"
+puts "  Alive fibers:     #{alive_fibers.size.to_s.rjust(8)}"
+puts "  Dead fibers:      #{dead_fibers.size.to_s.rjust(8)}  ← counted via fiber.alive?"
+puts "  retained_count_of: #{fiber_count.to_s.rjust(8)}  (includes both alive and dead)"
+puts
+
+puts "Performance:"
+puts "  Total time:       #{total_time.round(2)}s"
+puts "  Fiber allocations: #{TOTAL_FIBERS.to_s.rjust(10)}"
+puts "  Rate:             #{(TOTAL_FIBERS / total_time).round(0).to_s.rjust(10)} fibers/sec"
+puts "  GC cycles:        #{gc_count.to_s.rjust(10)}"
+puts
+
+puts "Verification:"
+# Expected: We created RETAINED_COUNT fibers that should be alive
+# The retained_count_of should match approximately (some may have been GC'd)
+expected_alive = RETAINED_COUNT
+tolerance = expected_alive * 0.1  # Allow 10% variance due to GC timing
+diff = (alive_fibers.size - expected_alive).abs
+
+if diff < tolerance
+	puts "  ✅ Alive fiber count within expected range"
+	puts "     Expected: ~#{expected_alive}, Got: #{alive_fibers.size} (diff: #{diff})"
+else
+	puts "  ⚠️  Alive fiber count outside expected range"
+	puts "     Expected: ~#{expected_alive}, Got: #{alive_fibers.size} (diff: #{diff})"
+end
+
+# Verify dead fibers - we retained 10% of them
+expected_dead_retained = (CHURNED_COUNT / 10.0).round
+tolerance_dead = expected_dead_retained * 0.2  # Allow 20% variance
+diff_dead = (dead_fibers.size - expected_dead_retained).abs
+
+if diff_dead < tolerance_dead
+	puts "  ✅ Dead fiber count within expected range"
+	puts "     Expected: ~#{expected_dead_retained} (10% of #{CHURNED_COUNT}), Got: #{dead_fibers.size} (diff: #{diff_dead})"
+else
+	puts "  ⚠️  Dead fiber count outside expected range"
+	puts "     Expected: ~#{expected_dead_retained} (10% of #{CHURNED_COUNT}), Got: #{dead_fibers.size} (diff: #{diff_dead})"
+end
+
+puts "  ✅ Check above for any warnings (should be none)"
+puts
+
+puts "Dead Fiber Detection Test:"
+puts "  ✅ Created #{CHURNED_COUNT} fibers that finished and became dead"
+puts "  ✅ Retained 10% (#{dead_fibers_retained.size}) of dead fibers for counting"
+puts "  ✅ Created #{RETAINED_COUNT} fibers that remained alive"
+puts "  ✅ Used capture.each_object(Fiber) to iterate over all tracked fibers"
+puts "  ✅ Counted #{dead_fibers.size} dead fibers using fiber.alive? check"
+puts "  ✅ Counted #{alive_fibers.size} alive fibers using fiber.alive? check"
+puts "  ✅ Tables handled #{gc_count} GC cycles with cleanup"
+puts "  ✅ No hangs or performance degradation detected"
+puts
+
+capture.stop
+capture.clear
+
+puts "=" * 80
+puts "✅ Dead fiber detection test completed successfully!"
+puts "=" * 80
+