Madeleine will check every hour if there are new commands in the log or 24 hours have passed since last snapshot, and take snapshot if either of these conditions is true

app/controllers/wiki_controller.rb

@@ -79,7 +79,7 @@ class WikiController < ApplicationController
   end
 
   def export_pdf
-    file_name = "#{web.address}-tex-#{web.revised_on.strftime("%Y-%m-%d-%H-%M")}"
+    file_name = "#{web.address}-tex-#{web.revised_on.strftime('%Y-%m-%d-%H-%M')}"
     file_path = WikiService.storage_path + file_name
 
     export_web_to_tex(file_path + ".tex") unless FileTest.exists?(file_path + ".tex")
@@ -88,7 +88,7 @@ class WikiController < ApplicationController
   end
 
   def export_tex
-    file_name = "#{web.address}-tex-#{web.revised_on.strftime("%Y-%m-%d-%H-%M")}.tex"
+    file_name = "#{web.address}-tex-#{web.revised_on.strftime('%Y-%m-%d-%H-%M')}.tex"
     file_path = WikiService.storage_path + file_name
 
     export_web_to_tex(file_path) unless FileTest.exists?(file_path)

app/models/wiki_service.rb

@@ -127,8 +127,8 @@ class WikiService
 end
 
 class MadeleineServer
-  SNAPSHOT_INTERVAL   = 60 * 60 * 24 # Each day
-  AUTOMATIC_SNAPSHOTS = true
+
+  attr_reader :storage_path
 
   # Clears all the command_log and snapshot files located in the storage directory, so the
   # database is essentially dropped and recreated as blank
@@ -145,22 +145,44 @@ class MadeleineServer
   end
 
   def initialize(service)
+    @storage_path = service.storage_path
     @server = Madeleine::Automatic::AutomaticSnapshotMadeleine.new(service.storage_path, 
       Madeleine::ZMarshal.new) {
       service.new
     }
-    start_snapshot_thread if AUTOMATIC_SNAPSHOTS
+    start_snapshot_thread
   end
 
   def system
     @server.system
   end
 
+  def command_log_present?
+    not Dir[storage_path + '/*.command_log'].empty?
+  end
+
   def start_snapshot_thread
     Thread.new(@server) {
+      hours_since_last_snapshot = 0
       while true
-        sleep(SNAPSHOT_INTERVAL)
-        @server.take_snapshot
+        begin
+          hours_since_last_snapshot += 1
+          # Take a snapshot if there is a command log, or 24 hours 
+          # have passed since the last snapshot
+          if command_log_present? or hours_since_last_snapshot >= 24 
+            ActionController::Base.logger.info "[#{Time.now.strftime('%Y-%m-%d %H:%M:%S')}] " +
+              'Taking a Madeleine snapshot'
+            @server.take_snapshot
+            hours_since_last_snapshot = 0
+          end
+          sleep(1.hour)
+        rescue => e
+          ActionController::Base.logger.error(e)
+          # wait for a minute (not to spoof the log with the same error)
+          # and go back into the loop, to keep trying
+          sleep(1.minute)
+          ActionController::Base.logger.info("Retrying to save a snapshot")
+        end
       end
     }
   end