allow rollback/locking by setting inS3:false when starting the archive process

services/track-changes/app/coffee/DocArchiveManager.coffee

@@ -38,12 +38,18 @@ module.exports = DocArchiveManager =
 			else
 				MongoManager.getLastCompressedUpdate doc_id, (error, update) ->
 					return callback(error) if error?
-					MongoAWS.archiveDocHistory project_id, doc_id, (error) ->
+					MongoManager.markDocHistoryAsArchiveInProgress doc_id, update, (error) ->
 						return callback(error) if error?
-						logger.log doc_id:doc_id, project_id:project_id, "exported document to S3"
-						MongoManager.markDocHistoryAsArchived doc_id, update, (error) ->
-							return callback(error) if error?
-							callback()
+						MongoAWS.archiveDocHistory project_id, doc_id, (error) ->
+							if error?
+								MongoManager.clearDocHistoryAsArchiveInProgress doc_id, update, (err) ->
+									return callback(err) if err?
+									callback(error)
+							else
+								logger.log doc_id:doc_id, project_id:project_id, "exported document to S3"
+								MongoManager.markDocHistoryAsArchived doc_id, update, (error) ->
+									return callback(error) if error?
+									callback()
 
 	unArchiveAllDocsChanges: (project_id, callback = (error, docs) ->) ->
 		DocstoreHandler.getAllDocs project_id, (error, docs) ->

services/track-changes/app/coffee/MongoManager.coffee

@@ -146,6 +146,12 @@ module.exports = MongoManager =
 	getArchivedDocChanges: (doc_id, callback)->
 		db.docHistory.count { doc_id: ObjectId(doc_id.toString()) , inS3: true }, {}, callback
 
+	markDocHistoryAsArchiveInProgress: (doc_id, update, callback) ->
+		db.docHistory.update { _id: update._id }, { $set : { inS3 : false } }, callback
+
+	clearDocHistoryAsArchiveInProgress: (doc_id, update, callback) ->
+		db.docHistory.update { _id: update._id }, { $set : { inS3 : false } }, callback
+
 	markDocHistoryAsArchived: (doc_id, update, callback)->
 		db.docHistory.update { _id: update._id }, { $set : { inS3 : true } }, (error)->
 			return callback(error) if error?
@@ -154,5 +160,6 @@ module.exports = MongoManager =
 				callback(error)
 
 	markDocHistoryAsUnarchived: (doc_id, callback)->
+		# note this removes any inS3 field, regardless of its value (true/false/null)
 		db.docHistory.update { doc_id: ObjectId(doc_id.toString()) }, { $unset : { inS3 : true } }, { multi: true }, (error)->
 			callback(error)

services/track-changes/app/coffee/UpdatesManager.coffee

@@ -103,7 +103,7 @@ module.exports = UpdatesManager =
 			MongoManager.getProjectUpdates project_id, options, (error, updates) ->
 				jobs = []
 				for update in updates
-					if update.inS3?
+					if update.inS3
 						do (update) ->
 							jobs.push (callback) -> DocArchiveManager.unArchiveDocChanges update.project_id, update.doc_id, callback
 				if jobs.length?