Log out and put the last update back when an error occurs

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

@@ -21,7 +21,13 @@ module.exports = HistoryManager =
 					rawUpdates.shift()
 
 				if rawUpdates[0]? and rawUpdates[0].v != lastCompressedUpdate.v + 1
-					return callback new Error("Tried to apply raw op at version #{rawUpdates[0].v} to last compressed update with version #{lastCompressedUpdate.v}")
+					error = new Error("Tried to apply raw op at version #{rawUpdates[0].v} to last compressed update with version #{lastCompressedUpdate.v}")
+					logger.error err: error, doc_id: doc_id, "inconsistent doc versions"
+					# Push the update back into Mongo - catching errors at this
+					# point is useless, we're already bailing
+					MongoManager.insertCompressedUpdates doc_id, [lastCompressedUpdate], () ->
+						return callback error
+					return
 
 			compressedUpdates = UpdateCompressor.compressRawUpdates lastCompressedUpdate, rawUpdates
 			MongoManager.insertCompressedUpdates doc_id, compressedUpdates, (error) ->

services/track-changes/test/unit/coffee/HistoryManager/HistoryManagerTests.coffee

@@ -12,7 +12,7 @@ describe "HistoryManager", ->
 			"./MongoManager" : @MongoManager = {}
 			"./RedisManager" : @RedisManager = {}
 			"./LockManager"  : @LockManager = {}
-			"logger-sharelatex": { log: sinon.stub() }
+			"logger-sharelatex": { log: sinon.stub(), error: sinon.stub() }
 		@doc_id = "doc-id-123"
 		@callback = sinon.stub()
 
@@ -111,6 +111,12 @@ describe "HistoryManager", ->
 						.calledWith(new Error("Tried to apply raw op at version 13 to last compressed update with version 11"))
 						.should.equal true
 
+				it "should put the popped update back into mongo", ->
+					@MongoManager.insertCompressedUpdates.calledOnce.should.equal true
+					@MongoManager.insertCompressedUpdates
+						.calledWith(@doc_id, [@lastCompressedUpdate])
+						.should.equal true
+
 	describe "processUncompressedUpdates", ->
 		describe "when there is fewer than one batch to send", ->
 			beforeEach ->