#428

backend/app/services/shared_resource_id_allocator.rb

@@ -13,42 +13,14 @@ class SharedResourceIdAllocator
           ['tag_description_versions', 'tag_id']],
       'wiki' => [['tag_group_versions', 'tag_group_id']] }.freeze
   LOCK_TIMEOUT = 10
+  TRANSACTION_LOCKS = ObjectSpace::WeakMap.new
 
   def self.assign! record
     space, tables = SPACES.find { |_name, names| names.include?(record.class.table_name) }
     raise ArgumentError, 'Unknown shared ID resource' unless tables
 
     connection = record.class.connection
-    transaction = record.class.current_transaction
-    unless transaction.open?
-      raise ActiveRecord::ActiveRecordError, 'Shared ID requires a transaction'
-    end
-
-    database = connection.pool.db_config.database
-    name = "btrc:ids:#{ Digest::SHA256.hexdigest(database)[0, 16] }:#{ space }"
-    quoted_name = connection.quote(name)
-    acquired = record.class.uncached do
-      connection.select_value("SELECT GET_LOCK(#{ quoted_name }, #{ LOCK_TIMEOUT })")
-    end
-    unless acquired.to_i == 1
-      raise ActiveRecord::LockWaitTimeout, "Shared ID lock unavailable: #{ space }"
-    end
-
-    release = lambda do
-      result = record.class.uncached do
-        connection.select_value("SELECT RELEASE_LOCK(#{ quoted_name })")
-      end
-      unless result.to_i == 1
-        raise ActiveRecord::ActiveRecordError, "Shared ID lock release failed: #{ space }"
-      end
-    end
-    begin
-      transaction.after_commit(&release)
-      transaction.after_rollback(&release)
-    rescue StandardError
-      release.call
-      raise
-    end
+    lock_space!(record.class, space)
 
     # 明示-tic な Id. 指定は許可する．
     return if record.id.present?
@@ -66,6 +38,47 @@ class SharedResourceIdAllocator
     record.id = next_id
   end
 
+  def self.lock_space! record_class, space
+    raise ArgumentError, 'Unknown shared ID resource' unless SPACES.key?(space)
+
+    connection = record_class.connection
+    transaction = record_class.current_transaction
+    unless transaction.open?
+      raise ActiveRecord::ActiveRecordError, 'Shared ID requires a transaction'
+    end
+
+    database = connection.pool.db_config.database
+    name = "btrc:ids:#{ Digest::SHA256.hexdigest(database)[0, 16] }:#{ space }"
+    held_locks = TRANSACTION_LOCKS[transaction] ||= {}
+    return if held_locks.key?(name)
+
+    quoted_name = connection.quote(name)
+    acquired = record_class.uncached do
+      connection.select_value("SELECT GET_LOCK(#{ quoted_name }, #{ LOCK_TIMEOUT })")
+    end
+    unless acquired.to_i == 1
+      raise ActiveRecord::LockWaitTimeout, "Shared ID lock unavailable: #{ space }"
+    end
+    held_locks[name] = true
+
+    release = lambda do
+      held_locks.delete(name)
+      result = record_class.uncached do
+        connection.select_value("SELECT RELEASE_LOCK(#{ quoted_name })")
+      end
+      unless result.to_i == 1
+        raise ActiveRecord::ActiveRecordError, "Shared ID lock release failed: #{ space }"
+      end
+    end
+    begin
+      transaction.after_commit(&release)
+      transaction.after_rollback(&release)
+    rescue StandardError
+      release.call
+      raise
+    end
+  end
+
   def self.next_ids connection, tables
     expiry = connection.select_value('SELECT @@SESSION.information_schema_stats_expiry').to_i
     begin