(DIO-2675) Undo pool size template overrides

This implements a delete method for pooltemplate and poolsize. The API
removes the override from Redis and then adds an entry in Redis that
causes the pool manager to wake up and process the removal of the
override.

To facilitate this, a new variable has been created in lib/vmpooler.rb
to hold a copy of the original / pre-override config. This supplemental
copy of the pools is then indexed for use as a reference.

When pool manager wakes up to process an override removal, it looks up
the pre-override value from the config via the new variables mentioned
above.

Just as with entering overrides, no restart is needed. Template and pool
size changes are logged so that anyone watching or reviewing the logs
can see what happened when. The new API endpoints also return values for
both the pre-revert and post-revert value.

lib/vmpooler/pool_manager.rb

@@ -784,6 +784,10 @@ module Vmpooler
     #   - Fires when a pool reset is requested
     #   - Additional options
     #       :poolname
+    # :undo_override
+    #   - Fires when a pool override removal is requested
+    #   - Additional options
+    #       :poolname
     #
     def sleep_with_wakeup_events(loop_delay, wakeup_period = 5, options = {})
       exit_by = Time.now + loop_delay
@@ -826,6 +830,11 @@ module Vmpooler
               break if pending
             end
 
+            if options[:undo_override]
+              break if redis.sismember('vmpooler__pool__undo_template_override', options[:poolname])
+              break if redis.sismember('vmpooler__pool__undo_size_override', options[:poolname])
+            end
+
             if options[:pending_vm]
               pending_vm_count = redis.scard("vmpooler__pending__#{options[:poolname]}")
               break unless pending_vm_count == 0
@@ -880,7 +889,7 @@ module Vmpooler
               loop_delay = (loop_delay * loop_delay_decay).to_i
               loop_delay = loop_delay_max if loop_delay > loop_delay_max
             end
-            sleep_with_wakeup_events(loop_delay, loop_delay_min, pool_size_change: true, poolname: pool['name'], pool_template_change: true, clone_target_change: true, pending_vm: true, pool_reset: true)
+            sleep_with_wakeup_events(loop_delay, loop_delay_min, pool_size_change: true, poolname: pool['name'], pool_template_change: true, clone_target_change: true, pending_vm: true, pool_reset: true, undo_override: true)
 
             unless maxloop == 0
               break if loop_count >= maxloop
@@ -1040,15 +1049,18 @@ module Vmpooler
       return if mutex.locked?
 
       @redis.with_metrics do |redis|
-        poolsize = redis.hget('vmpooler__config__poolsize', pool['name'])
-        break if poolsize.nil?
+        pool_size_requested = redis.hget('vmpooler__config__poolsize', pool['name'])
+        break if pool_size_requested.nil?
 
-        poolsize = Integer(poolsize)
-        break if poolsize == pool['size']
+        pool_size_requested = Integer(pool_size_requested)
+        pool_size_currently = pool['size']
+        break if pool_size_requested == pool_size_currently
 
         mutex.synchronize do
-          pool['size'] = poolsize
+          pool['size'] = pool_size_requested
         end
+
+        $logger.log('s', "[*] [#{pool['name']}] size updated from #{pool_size_currently} to #{pool_size_requested}")
       end
     end
 
@@ -1066,6 +1078,38 @@ module Vmpooler
       end
     end
 
+    def undo_override(pool, provider)
+      poolname = pool['name']
+      mutex = pool_mutex(poolname)
+      return if mutex.locked?
+
+      @redis.with_metrics do |redis|
+        break unless redis.sismember('vmpooler__pool__undo_template_override', poolname)
+
+        redis.srem('vmpooler__pool__undo_template_override', poolname)
+        template_now = pool['template']
+        template_original = $config[:pools_at_startup][$config[:pool_index][poolname]]['template']
+
+        mutex.synchronize do
+          update_pool_template(pool, provider, template_original, template_now, redis)
+        end
+      end
+
+      @redis.with_metrics do |redis|
+        break unless redis.sismember('vmpooler__pool__undo_size_override', poolname)
+
+        redis.srem('vmpooler__pool__undo_size_override', poolname)
+        pool_size_now = pool['size']
+        pool_size_original = $config[:pools_at_startup][$config[:pool_index][poolname]]['size']
+
+        mutex.synchronize do
+          pool['size'] = pool_size_original
+        end
+
+        $logger.log('s', "[*] [#{poolname}] size updated from #{pool_size_now} to #{pool_size_original}")
+      end
+    end
+
     def create_inventory(pool, provider, pool_check_response)
       inventory = {}
       begin
@@ -1300,6 +1344,9 @@ module Vmpooler
       # Reset a pool when poolreset is requested from the API
       reset_pool(pool)
 
+      # Undo overrides submitted via the api
+      undo_override(pool, provider)
+
       pool_check_response
     end