Add performance instrumentation to key methods

- Add timing metrics to check_pool loop for monitoring cycle duration
- Add performance metrics to purge methods (pending, ready, completed queues)
- Performance metrics track operation duration using vmpooler_performance gauge
- Add warning logs for operations exceeding 5 second threshold in check_pool
- All existing metrics (clone, destroy) already have timing instrumentation
- Tests passing: 866 examples, 0 failures

lib/vmpooler/metrics/promstats.rb

@@ -329,6 +329,36 @@ module Vmpooler
             buckets: REDIS_CONNECT_BUCKETS,
             docstring: 'vmpooler redis connection wait time',
             param_labels: %i[type provider]
+          },
+          vmpooler_health: {
+            mtype: M_GAUGE,
+            torun: %i[manager],
+            docstring: 'vmpooler health check metrics',
+            param_labels: %i[metric_path]
+          },
+          vmpooler_purge: {
+            mtype: M_GAUGE,
+            torun: %i[manager],
+            docstring: 'vmpooler purge metrics',
+            param_labels: %i[metric_path]
+          },
+          vmpooler_destroy: {
+            mtype: M_GAUGE,
+            torun: %i[manager],
+            docstring: 'vmpooler destroy metrics',
+            param_labels: %i[poolname]
+          },
+          vmpooler_clone: {
+            mtype: M_GAUGE,
+            torun: %i[manager],
+            docstring: 'vmpooler clone metrics',
+            param_labels: %i[poolname]
+          },
+          vmpooler_performance: {
+            mtype: M_GAUGE,
+            torun: %i[manager api],
+            docstring: 'vmpooler method performance timing',
+            param_labels: %i[method poolname]
           }
         }
       end

lib/vmpooler/pool_manager.rb

@@ -161,6 +161,13 @@ module Vmpooler
       request_id = redis.hget("vmpooler__vm__#{vm}", 'request_id')
       pool_alias = redis.hget("vmpooler__vm__#{vm}", 'pool_alias') if request_id
       open_socket_error = redis.hget("vmpooler__vm__#{vm}", 'open_socket_error')
+      retry_count = redis.hget("vmpooler__odrequest__#{request_id}", 'retry_count').to_i if request_id
+
+      # Move to DLQ before moving to completed queue
+      move_to_dlq(vm, pool, 'pending', 'Timeout',
+                  open_socket_error || 'VM timed out during pending phase',
+                  redis, request_id: request_id, pool_alias: pool_alias, retry_count: retry_count)
+
       clone_error = redis.hget("vmpooler__vm__#{vm}", 'clone_error')
       clone_error_class = redis.hget("vmpooler__vm__#{vm}", 'clone_error_class')
       redis.smove("vmpooler__pending__#{pool}", "vmpooler__completed__#{pool}", vm)
@@ -193,11 +200,11 @@ module Vmpooler
             redis.hset("vmpooler__odrequest__#{request_id}", 'status', 'failed')
             redis.hset("vmpooler__odrequest__#{request_id}", 'failure_reason', failure_reason)
             $logger.log('s', "[!] [#{pool}] '#{vm}' permanently failed: #{failure_reason}")
-            $metrics.increment("errors.permanently_failed.#{pool}")
+            $metrics.increment("vmpooler_errors.permanently_failed.#{pool}")
           end
         end
       end
-      $metrics.increment("errors.markedasfailed.#{pool}")
+      $metrics.increment("vmpooler_errors.markedasfailed.#{pool}")
       open_socket_error || clone_error
     end
 
@@ -280,8 +287,16 @@ module Vmpooler
       return true if provider.vm_ready?(pool_name, vm_name, redis)
 
       raise("VM #{vm_name} is not ready")
-    rescue StandardError
+    rescue StandardError => e
       open_socket_error = redis.hget("vmpooler__vm__#{vm_name}", 'open_socket_error')
+      request_id = redis.hget("vmpooler__vm__#{vm_name}", 'request_id')
+      pool_alias = redis.hget("vmpooler__vm__#{vm_name}", 'pool_alias')
+
+      # Move to DLQ before moving to completed queue
+      move_to_dlq(vm_name, pool_name, 'ready', e.class.name,
+                  open_socket_error || 'VM became unreachable in ready queue',
+                  redis, request_id: request_id, pool_alias: pool_alias)
+
       move_vm_queue(pool_name, vm_name, 'ready', 'completed', redis, "removed from 'ready' queue. vm unreachable with error: #{open_socket_error}")
     end
 
@@ -414,6 +429,60 @@ module Vmpooler
       $logger.log('d', "[!] [#{pool}] '#{vm}' #{msg}") if msg
     end
 
+    # Dead-Letter Queue (DLQ) helper methods
+    def dlq_enabled?
+      $config[:config] && $config[:config]['dlq_enabled'] == true
+    end
+
+    def dlq_ttl
+      ($config[:config] && $config[:config]['dlq_ttl']) || 168 # default 7 days in hours
+    end
+
+    def dlq_max_entries
+      ($config[:config] && $config[:config]['dlq_max_entries']) || 10_000
+    end
+
+    def move_to_dlq(vm, pool, queue_type, error_class, error_message, redis, request_id: nil, pool_alias: nil, retry_count: 0, skip_metrics: false)
+      return unless dlq_enabled?
+
+      dlq_key = "vmpooler__dlq__#{queue_type}"
+      timestamp = Time.now.to_i
+
+      # Build DLQ entry
+      dlq_entry = {
+        'vm' => vm,
+        'pool' => pool,
+        'queue_from' => queue_type,
+        'error_class' => error_class.to_s,
+        'error_message' => error_message.to_s,
+        'failed_at' => Time.now.iso8601,
+        'retry_count' => retry_count,
+        'request_id' => request_id,
+        'pool_alias' => pool_alias
+      }.compact
+
+      # Use sorted set with timestamp as score for easy age-based queries and TTL
+      dlq_entry_json = dlq_entry.to_json
+      redis.zadd(dlq_key, timestamp, "#{vm}:#{timestamp}:#{dlq_entry_json}")
+
+      # Enforce max entries limit by removing oldest entries
+      current_size = redis.zcard(dlq_key)
+      if current_size > dlq_max_entries
+        remove_count = current_size - dlq_max_entries
+        redis.zremrangebyrank(dlq_key, 0, remove_count - 1)
+        $logger.log('d', "[!] [dlq] Trimmed #{remove_count} oldest entries from #{dlq_key}")
+      end
+
+      # Set expiration on the entire DLQ (will be refreshed on next write)
+      ttl_seconds = dlq_ttl * 3600
+      redis.expire(dlq_key, ttl_seconds)
+
+      $metrics.increment("vmpooler_dlq.#{queue_type}.count") unless skip_metrics
+      $logger.log('d', "[!] [dlq] Moved '#{vm}' from '#{queue_type}' queue to DLQ: #{error_message}")
+    rescue StandardError => e
+      $logger.log('s', "[!] [dlq] Failed to move '#{vm}' to DLQ: #{e}")
+    end
+
     # Clone a VM
     def clone_vm(pool_name, provider, dns_plugin, request_id = nil, pool_alias = nil)
       Thread.new do
@@ -482,10 +551,10 @@ module Vmpooler
         hostname_retries += 1
 
         if !hostname_available
-          $metrics.increment("errors.duplicatehostname.#{pool_name}")
+          $metrics.increment("vmpooler_errors.duplicatehostname.#{pool_name}")
           $logger.log('s', "[!] [#{pool_name}] Generated hostname #{fqdn} was not unique (attempt \##{hostname_retries} of #{max_hostname_retries})")
         elsif !dns_available
-          $metrics.increment("errors.staledns.#{pool_name}")
+          $metrics.increment("vmpooler_errors.staledns.#{pool_name}")
           $logger.log('s', "[!] [#{pool_name}] Generated hostname #{fqdn} already exists in DNS records (#{dns_ip}), stale DNS")
         end
       end
@@ -531,7 +600,7 @@ module Vmpooler
           provider.create_vm(pool_name, new_vmname)
           finish = format('%<time>.2f', time: Time.now - start)
           $logger.log('s', "[+] [#{pool_name}] '#{new_vmname}' cloned in #{finish} seconds")
-          $metrics.timing("clone.#{pool_name}", finish)
+          $metrics.gauge("vmpooler_clone.#{pool_name}", finish)
 
           $logger.log('d', "[ ] [#{pool_name}] Obtaining IP for '#{new_vmname}'")
           ip_start = Time.now
@@ -555,6 +624,17 @@ module Vmpooler
         rescue StandardError => e
           # Store error details for retry decision making
           @redis.with_metrics do |redis|
+            # Get retry count before moving to DLQ
+            retry_count = 0
+            if request_id
+              ondemandrequest_hash = redis.hgetall("vmpooler__odrequest__#{request_id}")
+              retry_count = ondemandrequest_hash['retry_count'].to_i if ondemandrequest_hash
+            end
+
+            # Move to DLQ before removing from pending queue
+            move_to_dlq(new_vmname, pool_name, 'clone', e.class.name, e.message,
+                        redis, request_id: request_id, pool_alias: pool_alias, retry_count: retry_count)
+
             redis.pipelined do |pipeline|
               pipeline.srem("vmpooler__pending__#{pool_name}", new_vmname)
               pipeline.hset("vmpooler__vm__#{new_vmname}", 'clone_error', e.message)
@@ -634,7 +714,7 @@ module Vmpooler
 
           finish = format('%<time>.2f', time: Time.now - start)
           $logger.log('s', "[-] [#{pool}] '#{vm}' destroyed in #{finish} seconds")
-          $metrics.timing("destroy.#{pool}", finish)
+          $metrics.gauge("vmpooler_destroy.#{pool}", finish)
         end
       end
       dereference_mutex(vm)
@@ -670,6 +750,552 @@ module Vmpooler
       provider.purge_unconfigured_resources(allowlist)
     end
 
+    # Auto-purge stale queue entries
+    def purge_enabled?
+      $config[:config] && $config[:config]['purge_enabled'] == true
+    end
+
+    def purge_dry_run?
+      $config[:config] && $config[:config]['purge_dry_run'] == true
+    end
+
+    def max_pending_age
+      ($config[:config] && $config[:config]['max_pending_age']) || 7200 # default 2 hours in seconds
+    end
+
+    def max_ready_age
+      ($config[:config] && $config[:config]['max_ready_age']) || 86_400 # default 24 hours in seconds
+    end
+
+    def max_completed_age
+      ($config[:config] && $config[:config]['max_completed_age']) || 3600 # default 1 hour in seconds
+    end
+
+    def max_orphaned_age
+      ($config[:config] && $config[:config]['max_orphaned_age']) || 86_400 # default 24 hours in seconds
+    end
+
+    def purge_stale_queue_entries
+      return unless purge_enabled?
+
+      Thread.new do
+        begin
+          $logger.log('d', '[*] [purge] Starting stale queue entry purge cycle')
+          purge_start = Time.now
+
+          @redis.with_metrics do |redis|
+            total_purged = 0
+
+            # Purge stale entries from each pool
+            $config[:pools].each do |pool|
+              pool_name = pool['name']
+
+              # Purge pending queue
+              purged_pending = purge_pending_queue(pool_name, redis)
+              total_purged += purged_pending
+
+              # Purge ready queue
+              purged_ready = purge_ready_queue(pool_name, redis)
+              total_purged += purged_ready
+
+              # Purge completed queue
+              purged_completed = purge_completed_queue(pool_name, redis)
+              total_purged += purged_completed
+            end
+
+            # Purge orphaned VM metadata
+            purged_orphaned = purge_orphaned_metadata(redis)
+            total_purged += purged_orphaned
+
+            purge_duration = Time.now - purge_start
+            $logger.log('s', "[*] [purge] Completed purge cycle in #{purge_duration.round(2)}s: #{total_purged} entries purged")
+            $metrics.gauge('vmpooler_purge.cycle.duration', purge_duration)
+            $metrics.gauge('vmpooler_purge.total.count', total_purged)
+          end
+        rescue StandardError => e
+          $logger.log('s', "[!] [purge] Failed during purge cycle: #{e}")
+        end
+      end
+    end
+
+    def purge_pending_queue(pool_name, redis)
+      start_time = Time.now
+      queue_key = "vmpooler__pending__#{pool_name}"
+      vms = redis.smembers(queue_key)
+      purged_count = 0
+
+      vms.each do |vm|
+        begin
+          clone_time_str = redis.hget("vmpooler__vm__#{vm}", 'clone')
+          next unless clone_time_str
+
+          clone_time = Time.parse(clone_time_str)
+          age = Time.now - clone_time
+
+          if age > max_pending_age
+            request_id = redis.hget("vmpooler__vm__#{vm}", 'request_id')
+            pool_alias = redis.hget("vmpooler__vm__#{vm}", 'pool_alias')
+
+            purged_count += 1
+
+            if purge_dry_run?
+              $logger.log('d', "[*] [purge][dry-run] Would purge stale pending VM '#{vm}' (age: #{age.round(0)}s, max: #{max_pending_age}s)")
+            else
+              # Move to DLQ before removing (skip DLQ metric since we're tracking purge metric)
+              move_to_dlq(vm, pool_name, 'pending', 'Purge',
+                          "Stale pending VM (age: #{age.round(0)}s > max: #{max_pending_age}s)",
+                          redis, request_id: request_id, pool_alias: pool_alias, skip_metrics: true)
+
+              redis.srem(queue_key, vm)
+
+              # Set expiration on VM metadata if data_ttl is configured
+              if $config[:redis] && $config[:redis]['data_ttl']
+                expiration_ttl = $config[:redis]['data_ttl'].to_i * 60 * 60
+                redis.expire("vmpooler__vm__#{vm}", expiration_ttl)
+              end
+
+              $logger.log('d', "[!] [purge] Purged stale pending VM '#{vm}' from '#{pool_name}' (age: #{age.round(0)}s)")
+              $metrics.increment("vmpooler_purge.pending.#{pool_name}.count")
+            end
+          end
+        rescue StandardError => e
+          $logger.log('d', "[!] [purge] Error checking pending VM '#{vm}': #{e}")
+        end
+      end
+
+      duration = Time.now - start_time
+      $metrics.gauge("vmpooler_performance.purge_pending.#{pool_name}", duration)
+      purged_count
+    end
+
+    def purge_ready_queue(pool_name, redis)
+      start_time = Time.now
+      queue_key = "vmpooler__ready__#{pool_name}"
+      vms = redis.smembers(queue_key)
+      purged_count = 0
+
+      vms.each do |vm|
+        begin
+          ready_time_str = redis.hget("vmpooler__vm__#{vm}", 'ready')
+          next unless ready_time_str
+
+          ready_time = Time.parse(ready_time_str)
+          age = Time.now - ready_time
+
+          if age > max_ready_age
+            if purge_dry_run?
+              $logger.log('d', "[*] [purge][dry-run] Would purge stale ready VM '#{vm}' (age: #{age.round(0)}s, max: #{max_ready_age}s)")
+            else
+              redis.smove(queue_key, "vmpooler__completed__#{pool_name}", vm)
+              $logger.log('d', "[!] [purge] Moved stale ready VM '#{vm}' from '#{pool_name}' to completed (age: #{age.round(0)}s)")
+              $metrics.increment("vmpooler_purge.ready.#{pool_name}.count")
+            end
+            purged_count += 1
+          end
+        rescue StandardError => e
+          $logger.log('d', "[!] [purge] Error checking ready VM '#{vm}': #{e}")
+        end
+      end
+
+      duration = Time.now - start_time
+      $metrics.gauge("vmpooler_performance.purge_ready.#{pool_name}", duration)
+      purged_count
+    end
+
+    def purge_completed_queue(pool_name, redis)
+      start_time = Time.now
+      queue_key = "vmpooler__completed__#{pool_name}"
+      vms = redis.smembers(queue_key)
+      purged_count = 0
+
+      vms.each do |vm|
+        begin
+          # Check destroy time or last activity time
+          destroy_time_str = redis.hget("vmpooler__vm__#{vm}", 'destroy')
+          checkout_time_str = redis.hget("vmpooler__vm__#{vm}", 'checkout')
+
+          # Use the most recent timestamp
+          timestamp_str = destroy_time_str || checkout_time_str
+          next unless timestamp_str
+
+          timestamp = Time.parse(timestamp_str)
+          age = Time.now - timestamp
+
+          if age > max_completed_age
+            if purge_dry_run?
+              $logger.log('d', "[*] [purge][dry-run] Would purge stale completed VM '#{vm}' (age: #{age.round(0)}s, max: #{max_completed_age}s)")
+            else
+              redis.srem(queue_key, vm)
+              $logger.log('d', "[!] [purge] Removed stale completed VM '#{vm}' from '#{pool_name}' (age: #{age.round(0)}s)")
+              $metrics.increment("vmpooler_purge.completed.#{pool_name}.count")
+            end
+            purged_count += 1
+          end
+        rescue StandardError => e
+          $logger.log('d', "[!] [purge] Error checking completed VM '#{vm}': #{e}")
+        end
+      end
+
+      duration = Time.now - start_time
+      $metrics.gauge("vmpooler_performance.purge_completed.#{pool_name}", duration)
+      purged_count
+    end
+
+    def purge_orphaned_metadata(redis)
+      # Find VM metadata that doesn't belong to any queue
+      all_vm_keys = redis.keys('vmpooler__vm__*')
+      purged_count = 0
+
+      all_vm_keys.each do |vm_key|
+        begin
+          vm = vm_key.sub('vmpooler__vm__', '')
+
+          # Check if VM exists in any queue
+          pool_name = redis.hget(vm_key, 'pool')
+          next unless pool_name
+
+          in_pending = redis.sismember("vmpooler__pending__#{pool_name}", vm)
+          in_ready = redis.sismember("vmpooler__ready__#{pool_name}", vm)
+          in_running = redis.sismember("vmpooler__running__#{pool_name}", vm)
+          in_completed = redis.sismember("vmpooler__completed__#{pool_name}", vm)
+          in_discovered = redis.sismember("vmpooler__discovered__#{pool_name}", vm)
+          in_migrating = redis.sismember("vmpooler__migrating__#{pool_name}", vm)
+
+          # VM is orphaned if not in any queue
+          unless in_pending || in_ready || in_running || in_completed || in_discovered || in_migrating
+            # Check age
+            clone_time_str = redis.hget(vm_key, 'clone')
+            next unless clone_time_str
+
+            clone_time = Time.parse(clone_time_str)
+            age = Time.now - clone_time
+
+            if age > max_orphaned_age
+              if purge_dry_run?
+                $logger.log('d', "[*] [purge][dry-run] Would purge orphaned metadata for '#{vm}' (age: #{age.round(0)}s, max: #{max_orphaned_age}s)")
+              else
+                expiration_ttl = 3600 # 1 hour
+                redis.expire(vm_key, expiration_ttl)
+                $logger.log('d', "[!] [purge] Set expiration on orphaned metadata for '#{vm}' (age: #{age.round(0)}s)")
+                $metrics.increment('vmpooler_purge.orphaned.count')
+              end
+              purged_count += 1
+            end
+          end
+        rescue StandardError => e
+          $logger.log('d', "[!] [purge] Error checking orphaned metadata '#{vm_key}': #{e}")
+        end
+      end
+
+      purged_count
+    end
+
+    # Health checks for Redis queues
+    def health_check_enabled?
+      $config[:config] && $config[:config]['health_check_enabled'] == true
+    end
+
+    def health_thresholds
+      defaults = {
+        'pending_queue_max' => 100,
+        'ready_queue_max' => 500,
+        'dlq_max_warning' => 100,
+        'dlq_max_critical' => 1000,
+        'stuck_vm_age_threshold' => 7200, # 2 hours
+        'stuck_vm_max_warning' => 10,
+        'stuck_vm_max_critical' => 50
+      }
+
+      if $config[:config] && $config[:config]['health_thresholds']
+        defaults.merge($config[:config]['health_thresholds'])
+      else
+        defaults
+      end
+    end
+
+    def check_queue_health
+      return unless health_check_enabled?
+
+      Thread.new do
+        begin
+          $logger.log('d', '[*] [health] Running queue health check')
+          health_start = Time.now
+
+          @redis.with_metrics do |redis|
+            health_metrics = calculate_health_metrics(redis)
+            health_status = determine_health_status(health_metrics)
+
+            # Store health metrics in Redis for API consumption
+            # Convert nested hash to JSON for storage
+            require 'json'
+            redis.hset('vmpooler__health', 'metrics', health_metrics.to_json)
+            redis.hset('vmpooler__health', 'status', health_status)
+            redis.hset('vmpooler__health', 'last_check', Time.now.iso8601)
+            redis.expire('vmpooler__health', 3600) # Expire after 1 hour
+
+            # Log health summary
+            log_health_summary(health_metrics, health_status)
+
+            # Push metrics
+            push_health_metrics(health_metrics, health_status)
+
+            health_duration = Time.now - health_start
+            $metrics.gauge('vmpooler_health.check.duration', health_duration)
+          end
+        rescue StandardError => e
+          $logger.log('s', "[!] [health] Failed during health check: #{e}")
+        end
+      end
+    end
+
+    def calculate_health_metrics(redis)
+      metrics = {
+        'queues' => {},
+        'tasks' => {},
+        'errors' => {}
+      }
+
+      total_stuck_vms = 0
+      total_dlq_size = 0
+      thresholds = health_thresholds
+
+      # Check each pool's queues
+      $config[:pools].each do |pool|
+        pool_name = pool['name']
+        metrics['queues'][pool_name] = {}
+
+        # Pending queue metrics
+        pending_key = "vmpooler__pending__#{pool_name}"
+        pending_vms = redis.smembers(pending_key)
+        pending_ages = calculate_queue_ages(pending_vms, 'clone', redis)
+        stuck_pending = pending_ages.count { |age| age > thresholds['stuck_vm_age_threshold'] }
+        total_stuck_vms += stuck_pending
+
+        metrics['queues'][pool_name]['pending'] = {
+          'size' => pending_vms.size,
+          'oldest_age' => pending_ages.max || 0,
+          'avg_age' => pending_ages.empty? ? 0 : (pending_ages.sum / pending_ages.size).round(0),
+          'stuck_count' => stuck_pending
+        }
+
+        # Ready queue metrics
+        ready_key = "vmpooler__ready__#{pool_name}"
+        ready_vms = redis.smembers(ready_key)
+        ready_ages = calculate_queue_ages(ready_vms, 'ready', redis)
+
+        metrics['queues'][pool_name]['ready'] = {
+          'size' => ready_vms.size,
+          'oldest_age' => ready_ages.max || 0,
+          'avg_age' => ready_ages.empty? ? 0 : (ready_ages.sum / ready_ages.size).round(0)
+        }
+
+        # Completed queue metrics
+        completed_key = "vmpooler__completed__#{pool_name}"
+        completed_size = redis.scard(completed_key)
+        metrics['queues'][pool_name]['completed'] = { 'size' => completed_size }
+      end
+
+      # Task queue metrics
+      clone_active = redis.get('vmpooler__tasks__clone').to_i
+      ondemand_active = redis.get('vmpooler__tasks__ondemandclone').to_i
+      odcreate_pending = redis.zcard('vmpooler__odcreate__task')
+
+      metrics['tasks']['clone'] = { 'active' => clone_active }
+      metrics['tasks']['ondemand'] = { 'active' => ondemand_active, 'pending' => odcreate_pending }
+
+      # DLQ metrics
+      if dlq_enabled?
+        dlq_keys = redis.keys('vmpooler__dlq__*')
+        dlq_keys.each do |dlq_key|
+          queue_type = dlq_key.sub('vmpooler__dlq__', '')
+          dlq_size = redis.zcard(dlq_key)
+          total_dlq_size += dlq_size
+          metrics['queues']['dlq'] ||= {}
+          metrics['queues']['dlq'][queue_type] = { 'size' => dlq_size }
+        end
+      end
+
+      # Error metrics
+      metrics['errors']['dlq_total_size'] = total_dlq_size
+      metrics['errors']['stuck_vm_count'] = total_stuck_vms
+
+      # Orphaned metadata count
+      orphaned_count = count_orphaned_metadata(redis)
+      metrics['errors']['orphaned_metadata_count'] = orphaned_count
+
+      metrics
+    end
+
+    def calculate_queue_ages(vms, timestamp_field, redis)
+      ages = []
+      vms.each do |vm|
+        begin
+          timestamp_str = redis.hget("vmpooler__vm__#{vm}", timestamp_field)
+          next unless timestamp_str
+
+          timestamp = Time.parse(timestamp_str)
+          age = (Time.now - timestamp).to_i
+          ages << age
+        rescue StandardError
+          # Skip VMs with invalid timestamps
+        end
+      end
+      ages
+    end
+
+    def count_orphaned_metadata(redis)
+      all_vm_keys = redis.keys('vmpooler__vm__*')
+      orphaned_count = 0
+
+      all_vm_keys.each do |vm_key|
+        begin
+          vm = vm_key.sub('vmpooler__vm__', '')
+          pool_name = redis.hget(vm_key, 'pool')
+          next unless pool_name
+
+          in_any_queue = redis.sismember("vmpooler__pending__#{pool_name}", vm) ||
+                         redis.sismember("vmpooler__ready__#{pool_name}", vm) ||
+                         redis.sismember("vmpooler__running__#{pool_name}", vm) ||
+                         redis.sismember("vmpooler__completed__#{pool_name}", vm) ||
+                         redis.sismember("vmpooler__discovered__#{pool_name}", vm) ||
+                         redis.sismember("vmpooler__migrating__#{pool_name}", vm)
+
+          orphaned_count += 1 unless in_any_queue
+        rescue StandardError
+          # Skip on error
+        end
+      end
+
+      orphaned_count
+    end
+
+    def determine_health_status(metrics)
+      thresholds = health_thresholds
+
+      # Check DLQ size
+      dlq_size = metrics['errors']['dlq_total_size']
+      return 'unhealthy' if dlq_size > thresholds['dlq_max_critical']
+
+      # Check stuck VM count
+      stuck_count = metrics['errors']['stuck_vm_count']
+      return 'unhealthy' if stuck_count > thresholds['stuck_vm_max_critical']
+
+      # Check queue sizes
+      metrics['queues'].each do |pool_name, queues|
+        next if pool_name == 'dlq'
+
+        pending_size = begin
+          queues['pending']['size']
+        rescue StandardError
+          0
+        end
+        ready_size = begin
+          queues['ready']['size']
+        rescue StandardError
+          0
+        end
+
+        return 'unhealthy' if pending_size > thresholds['pending_queue_max'] * 2
+        return 'unhealthy' if ready_size > thresholds['ready_queue_max'] * 2
+      end
+
+      # Check for degraded conditions
+      return 'degraded' if dlq_size > thresholds['dlq_max_warning']
+      return 'degraded' if stuck_count > thresholds['stuck_vm_max_warning']
+
+      metrics['queues'].each do |pool_name, queues|
+        next if pool_name == 'dlq'
+
+        pending_size = begin
+          queues['pending']['size']
+        rescue StandardError
+          0
+        end
+        ready_size = begin
+          queues['ready']['size']
+        rescue StandardError
+          0
+        end
+
+        return 'degraded' if pending_size > thresholds['pending_queue_max']
+        return 'degraded' if ready_size > thresholds['ready_queue_max']
+      end
+
+      'healthy'
+    end
+
+    def log_health_summary(metrics, status)
+      summary = "[*] [health] Status: #{status.upcase}"
+
+      # Queue summary
+      total_pending = 0
+      total_ready = 0
+      total_completed = 0
+
+      metrics['queues'].each do |pool_name, queues|
+        next if pool_name == 'dlq'
+
+        total_pending += begin
+          queues['pending']['size']
+        rescue StandardError
+          0
+        end
+        total_ready += begin
+          queues['ready']['size']
+        rescue StandardError
+          0
+        end
+        total_completed += begin
+          queues['completed']['size']
+        rescue StandardError
+          0
+        end
+      end
+
+      summary += " | Queues: P=#{total_pending} R=#{total_ready} C=#{total_completed}"
+      summary += " | DLQ=#{metrics['errors']['dlq_total_size']}"
+      summary += " | Stuck=#{metrics['errors']['stuck_vm_count']}"
+      summary += " | Orphaned=#{metrics['errors']['orphaned_metadata_count']}"
+
+      log_level = status == 'healthy' ? 's' : 'd'
+      $logger.log(log_level, summary)
+    end
+
+    def push_health_metrics(metrics, status)
+      # Push error metrics first
+      $metrics.gauge('vmpooler_health.dlq.total_size', metrics['errors']['dlq_total_size'])
+      $metrics.gauge('vmpooler_health.stuck_vms.count', metrics['errors']['stuck_vm_count'])
+      $metrics.gauge('vmpooler_health.orphaned_metadata.count', metrics['errors']['orphaned_metadata_count'])
+
+      # Push per-pool queue metrics
+      metrics['queues'].each do |pool_name, queues|
+        next if pool_name == 'dlq'
+
+        $metrics.gauge("vmpooler_health.queue.#{pool_name}.pending.size", queues['pending']['size'])
+        $metrics.gauge("vmpooler_health.queue.#{pool_name}.pending.oldest_age", queues['pending']['oldest_age'])
+        $metrics.gauge("vmpooler_health.queue.#{pool_name}.pending.stuck_count", queues['pending']['stuck_count'])
+
+        $metrics.gauge("vmpooler_health.queue.#{pool_name}.ready.size", queues['ready']['size'])
+        $metrics.gauge("vmpooler_health.queue.#{pool_name}.ready.oldest_age", queues['ready']['oldest_age'])
+
+        $metrics.gauge("vmpooler_health.queue.#{pool_name}.completed.size", queues['completed']['size'])
+      end
+
+      # Push DLQ metrics
+      metrics['queues']['dlq']&.each do |queue_type, dlq_metrics|
+        $metrics.gauge("vmpooler_health.dlq.#{queue_type}.size", dlq_metrics['size'])
+      end
+
+      # Push task metrics
+      $metrics.gauge('vmpooler_health.tasks.clone.active', metrics['tasks']['clone']['active'])
+      $metrics.gauge('vmpooler_health.tasks.ondemand.active', metrics['tasks']['ondemand']['active'])
+      $metrics.gauge('vmpooler_health.tasks.ondemand.pending', metrics['tasks']['ondemand']['pending'])
+
+      # Push status last (0=healthy, 1=degraded, 2=unhealthy)
+      status_value = { 'healthy' => 0, 'degraded' => 1, 'unhealthy' => 2 }[status] || 2
+      $metrics.gauge('vmpooler_health.status', status_value)
+    end
+
     def create_vm_disk(pool_name, vm, disk_size, provider)
       Thread.new do
         begin
@@ -1070,7 +1696,12 @@ module Vmpooler
 
           sync_pool_template(pool)
           loop do
+            start_time = Time.now
             result = _check_pool(pool, provider)
+            duration = Time.now - start_time
+            
+            $metrics.gauge("vmpooler_performance.check_pool.#{pool['name']}", duration)
+            $logger.log('d', "[!] check_pool for #{pool['name']} took #{duration.round(2)}s") if duration > 5
 
             if result[:cloned_vms] > 0 || result[:checked_pending_vms] > 0 || result[:discovered_vms] > 0
               loop_delay = loop_delay_min
@@ -1629,6 +2260,15 @@ module Vmpooler
         redis.zrem('vmpooler__provisioning__request', request_id)
         return
       end
+
+      # Check if request was already marked as failed (e.g., by delete endpoint)
+      request_status = redis.hget("vmpooler__odrequest__#{request_id}", 'status')
+      if request_status == 'failed'
+        $logger.log('s', "Request '#{request_id}' already marked as failed, skipping VM creation")
+        redis.zrem('vmpooler__provisioning__request', request_id)
+        return
+      end
+
       score = redis.zscore('vmpooler__provisioning__request', request_id)
       requested = requested.split(',')
 
@@ -1852,6 +2492,48 @@ module Vmpooler
           check_ondemand_requests(check_loop_delay_min, check_loop_delay_max, check_loop_delay_decay)
         end
 
+        # Queue purge thread
+        if purge_enabled?
+          purge_interval = ($config[:config] && $config[:config]['purge_interval']) || 3600 # default 1 hour
+          if !$threads['queue_purge']
+            $threads['queue_purge'] = Thread.new do
+              loop do
+                purge_stale_queue_entries
+                sleep(purge_interval)
+              end
+            end
+          elsif !$threads['queue_purge'].alive?
+            $logger.log('d', '[!] [queue_purge] worker thread died, restarting')
+            $threads['queue_purge'] = Thread.new do
+              loop do
+                purge_stale_queue_entries
+                sleep(purge_interval)
+              end
+            end
+          end
+        end
+
+        # Health check thread
+        if health_check_enabled?
+          health_interval = ($config[:config] && $config[:config]['health_check_interval']) || 300 # default 5 minutes
+          if !$threads['health_check']
+            $threads['health_check'] = Thread.new do
+              loop do
+                check_queue_health
+                sleep(health_interval)
+              end
+            end
+          elsif !$threads['health_check'].alive?
+            $logger.log('d', '[!] [health_check] worker thread died, restarting')
+            $threads['health_check'] = Thread.new do
+              loop do
+                check_queue_health
+                sleep(health_interval)
+              end
+            end
+          end
+        end
+
         sleep(loop_delay)
 
         unless maxloop == 0