How to improve JSON deserialization speed in .Net? (JSON.net or other?)

Question

We're considering replacing (some or many) 'classic' SOAP XML WCF calls by JSON (WCF or other) calls, because of the lower overhead and ease of use directly in Javascript. For now, we've just added an additional Json endpoint to our web service and added WebInvoke attributes to some operations and tested them. Everything works fine, using C# .Net clients or Javascript clients. So far so good.

However, it seems like deserializing big JSON strings to objects in C# .Net is much slower than deserializing SOAP XML. Both are using DataContract and DataMember attributes (exact same DTO). My question is: is this expected? Is there anything we can do to optimize this performance? Or should we consider JSON only for smaller requests where we DO notice performance improvements.

For now we've chosen JSON.net for this test and even though it doesn't show in this test case, it's supposed to be faster than the .Net JSON serialization. Somehow the ServiceStack deserialization does not work at all (no error, returns null for the IList).

For the test we do a service call to collect a list of rooms. It returns a GetRoomListResponse and in case of returning 5 dummy rooms, the JSON looks like this:

{"Acknowledge":1,"Code":0,"Message":null,"ValidateErrors":null,"Exception":null,"RoomList":[{"Description":"DummyRoom","Id":"205305e6-9f7b-4a6a-a1de-c5933a45cac0","Location":{"Code":"123","Description":"Location 123","Id":"4268dd65-100d-47c8-a7fe-ea8bf26a7282","Number":5}},{"Description":"DummyRoom","Id":"aad737f7-0caa-4574-9ca5-f39964d50f41","Location":{"Code":"123","Description":"Location 123","Id":"b0325ff4-c169-4b56-bc89-166d4c6d9eeb","Number":5}},{"Description":"DummyRoom","Id":"c8caef4b-e708-48b3-948f-7a5cdb6979ef","Location":{"Code":"123","Description":"Location 123","Id":"11b3f513-d17a-4a00-aebb-4d92ce3f9ae8","Number":5}},{"Description":"DummyRoom","Id":"71376c49-ec41-4b12-b5b9-afff7da882c8","Location":{"Code":"123","Description":"Location 123","Id":"1a188f13-3be6-4bde-96a0-ef5e0ae4e437","Number":5}},{"Description":"DummyRoom","Id":"b947a594-209e-4195-a2c8-86f20eb883c4","Location":{"Code":"123","Description":"Location 123","Id":"053e9969-d0ed-4623-8a84-d32499b5a8a8","Number":5}}]} 

The Response and DTO's look like this:

[DataContract(Namespace = "bla")] public class GetRoomListResponse {     [DataMember]     public IList<Room> RoomList;      [DataMember]     public string Exception;      [DataMember]     public AcknowledgeType Acknowledge = AcknowledgeType.Success;      [DataMember]     public string Message;      [DataMember]     public int Code;      [DataMember]     public IList<string> ValidateErrors; }  [DataContract(Name = "Location", Namespace = "bla")] public class Location {     [DataMember]     public Guid Id { get; set; }      [DataMember]     public int Number { get; set; }      [DataMember]     public string Code { get; set; }      [DataMember]     public string Description { get; set; } }  [DataContract(Name = "Room", Namespace = "bla")] public class Room {     [DataMember]     public Guid Id { get; set; }      [DataMember]     public string Description { get; set; }      [DataMember]     public Location Location { get; set; } } 

Then our test code is as follows:

    static void Main(string[] args)     {         SoapLogin();          Console.WriteLine();          SoapGetRoomList();         SoapGetRoomList();         SoapGetRoomList();         SoapGetRoomList();         SoapGetRoomList();         SoapGetRoomList();         SoapGetRoomList();          Console.WriteLine();          JsonDotNetGetRoomList();         JsonDotNetGetRoomList();         JsonDotNetGetRoomList();         JsonDotNetGetRoomList();         JsonDotNetGetRoomList();         JsonDotNetGetRoomList();         JsonDotNetGetRoomList();          Console.ReadLine();     }      private static void SoapGetRoomList()     {         var request = new TestServiceReference.GetRoomListRequest()         {             Token = Token,         };          Stopwatch sw = Stopwatch.StartNew();          using (var client = new TestServiceReference.WARPServiceClient())         {             TestServiceReference.GetRoomListResponse response = client.GetRoomList(request);         }          sw.Stop();         Console.WriteLine("SOAP GetRoomList: " + sw.ElapsedMilliseconds);     }      private static void JsonDotNetGetRoomList()     {         var request = new GetRoomListRequest()         {             Token = Token,         };          Stopwatch sw = Stopwatch.StartNew();         long deserializationMillis;          using (WebClient client = new WebClient())         {             client.Headers["Content-type"] = "application/json";             client.Encoding = Encoding.UTF8;              string requestData = JsonConvert.SerializeObject(request, JsonSerializerSettings);              var responseData = client.UploadString(GetRoomListAddress, requestData);              Stopwatch sw2 = Stopwatch.StartNew();             var response = JsonConvert.DeserializeObject<GetRoomListResponse>(responseData, JsonSerializerSettings);             sw2.Stop();             deserializationMillis = sw2.ElapsedMilliseconds;         }          sw.Stop();         Console.WriteLine("JSON.Net GetRoomList: " + sw.ElapsedMilliseconds + " (deserialization time: " + deserializationMillis + ")");     }      private static JsonSerializerSettings JsonSerializerSettings     {         get         {             var serializerSettings = new JsonSerializerSettings();              serializerSettings.CheckAdditionalContent = false;             serializerSettings.ConstructorHandling = ConstructorHandling.Default;             serializerSettings.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;             serializerSettings.DefaultValueHandling = DefaultValueHandling.Ignore;             serializerSettings.NullValueHandling = NullValueHandling.Ignore;             serializerSettings.ObjectCreationHandling = ObjectCreationHandling.Replace;             serializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.None;             serializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Error;              return serializerSettings;         }     } 

Now we've run this application with returning 50, 500 and 5000 rooms. The objects are not very complex.

These are the results; times are in ms:

50 rooms:

SOAP GetRoomList: 37 SOAP GetRoomList: 5 SOAP GetRoomList: 4 SOAP GetRoomList: 4 SOAP GetRoomList: 9 SOAP GetRoomList: 5 SOAP GetRoomList: 5  JSON.Net GetRoomList: 289 (deserialization time: 91) JSON.Net GetRoomList: 3 (deserialization time: 0) JSON.Net GetRoomList: 2 (deserialization time: 0) JSON.Net GetRoomList: 2 (deserialization time: 0) JSON.Net GetRoomList: 2 (deserialization time: 0) JSON.Net GetRoomList: 2 (deserialization time: 0) JSON.Net GetRoomList: 2 (deserialization time: 0) 

500 rooms:

SOAP GetRoomList: 47 SOAP GetRoomList: 9 SOAP GetRoomList: 8 SOAP GetRoomList: 8 SOAP GetRoomList: 8 SOAP GetRoomList: 8 SOAP GetRoomList: 8  JSON.Net GetRoomList: 301 (deserialization time: 100) JSON.Net GetRoomList: 12 (deserialization time: 8) JSON.Net GetRoomList: 12 (deserialization time: 8) JSON.Net GetRoomList: 12 (deserialization time: 8) JSON.Net GetRoomList: 11 (deserialization time: 8) JSON.Net GetRoomList: 11 (deserialization time: 8) JSON.Net GetRoomList: 15 (deserialization time: 12) 

5000 rooms:

SOAP GetRoomList: 93 SOAP GetRoomList: 51 SOAP GetRoomList: 58 SOAP GetRoomList: 60 SOAP GetRoomList: 53 SOAP GetRoomList: 53 SOAP GetRoomList: 51  JSON.Net GetRoomList: 405 (deserialization time: 175) JSON.Net GetRoomList: 107 (deserialization time: 79) JSON.Net GetRoomList: 108 (deserialization time: 82) JSON.Net GetRoomList: 112 (deserialization time: 85) JSON.Net GetRoomList: 105 (deserialization time: 79) JSON.Net GetRoomList: 111 (deserialization time: 81) JSON.Net GetRoomList: 110 (deserialization time: 82) 

I'm running the application in release mode. Both client and server on same machine. As you can see, deserialization of many (of the same type of) objects takes much more time with JSON than the XML to object mapping that WCF SOAP uses. Hell, deserialization alone takes more time than the entire web service call using SOAP.

Is there an explanation for this? Does XML (or the WCF SOAP implementation) offer a big advantage in this area or are there any things I can change on the client side (I'd rather not change the service, but changing the client side DTO's is acceptable) to try to improve performance? It feels like I already selected some settings on the JSON.net side that should make it faster than default settings, no? What seems to be the bottleneck here?

Answer 1

I have spent a little bit more time reading about JSON.NET internals, and my conclusion is that the slowness is caused mostly by reflection.

On the JSON.NET site i have found some nice performance tips, and i tried pretty much everything (JObject.Parse, Custom Converters etc.) but i couldn't squeeze out any significant performance improvement. Then i read the most important note on the whole site:

If performance is important and you don't mind more code to get it then this is your best choice. Read more about using JsonReader/JsonWriter here

So i listened to the advice and i implemented a basic version of a JsonReader to read the string efficiently:

var reader = new JsonTextReader(new StringReader(jsonString));  var response = new GetRoomListResponse(); var currentProperty = string.Empty;  while (reader.Read()) {     if (reader.Value != null)     {         if (reader.TokenType == JsonToken.PropertyName)             currentProperty = reader.Value.ToString();          if (reader.TokenType == JsonToken.Integer && currentProperty == "Acknowledge")             response.Acknowledge = (AcknowledgeType)Int32.Parse(reader.Value.ToString());          if (reader.TokenType == JsonToken.Integer && currentProperty == "Code")             response.Code = Int32.Parse(reader.Value.ToString());          if (reader.TokenType == JsonToken.String && currentProperty == "Message")             response.Message = reader.Value.ToString();          if (reader.TokenType == JsonToken.String && currentProperty == "Exception")             response.Exception = reader.Value.ToString();          // Process Rooms and other stuff     }     else     {         // Process tracking the current nested element     } } 

I think the exercise is clear, and without doubt this is the best performance you can get out of JSON.NET.

Just this limited code is 12x faster than the Deserialize version on my box with 500 rooms, but of course the mapping is not completed. However, i am pretty sure it will be at least 5x faster than deserialization in the worst-case.

Check out this link for more info about the JsonReader and how to use it:

http://james.newtonking.com/json/help/html/ReadingWritingJSON.htm

Answer 2

I have now used the suggestions by both The ZenCoder and mythz and I have done more testing. I noticed an error in my first test setup as well, because while I built the tool in Release mode, I still started the test app from Visual Studio, which still added some debug overhead and this made a much bigger difference on the JSON.Net side compared to the SOAP XML side on my PC, so the difference in practice of the initial test results was quite a bit smaller already.

Either way, below are the results of collecting 5000 / 50000 rooms from the server (localhost), including mapping them to models.

5000 rooms:

----- Test results for JSON.Net (reflection) -----  GetRoomList (5000): 107 GetRoomList (5000): 60 GetRoomList (5000): 65 GetRoomList (5000): 62 GetRoomList (5000): 63  ----- Test results for ServiceStack (reflection) -----  GetRoomList (5000): 111 GetRoomList (5000): 62 GetRoomList (5000): 62 GetRoomList (5000): 60 GetRoomList (5000): 62  ----- Test results for SOAP Xml (manual mapping) -----  GetRoomList (5000): 101 GetRoomList (5000): 47 GetRoomList (5000): 51 GetRoomList (5000): 49 GetRoomList (5000): 51  ----- Test results for Json.Net (manual mapping) -----  GetRoomList (5000): 58 GetRoomList (5000): 47 GetRoomList (5000): 51 GetRoomList (5000): 49 GetRoomList (5000): 47  ----- Test results for ServiceStack (manual mapping) -----  GetRoomList (5000): 91 GetRoomList (5000): 79 GetRoomList (5000): 64 GetRoomList (5000): 66 GetRoomList (5000): 77 

50000 rooms:

----- Test results for JSON.Net (reflection) -----  GetRoomList (50000): 651 GetRoomList (50000): 628 GetRoomList (50000): 642 GetRoomList (50000): 625 GetRoomList (50000): 628  ----- Test results for ServiceStack (reflection) -----  GetRoomList (50000): 754 GetRoomList (50000): 674 GetRoomList (50000): 658 GetRoomList (50000): 657 GetRoomList (50000): 654  ----- Test results for SOAP Xml (manual mapping) -----  GetRoomList (50000): 567 GetRoomList (50000): 556 GetRoomList (50000): 561 GetRoomList (50000): 501 GetRoomList (50000): 543  ----- Test results for Json.Net (manual mapping) -----  GetRoomList (50000): 575 GetRoomList (50000): 569 GetRoomList (50000): 515 GetRoomList (50000): 539 GetRoomList (50000): 526  ----- Test results for ServiceStack (manual mapping) -----  GetRoomList (50000): 850 GetRoomList (50000): 796 GetRoomList (50000): 784 GetRoomList (50000): 805 GetRoomList (50000): 768 

Legend:

• JSON.Net (reflection) -> JsonConvert.DeserializeObject (same JSON.Net code as above)
• ServiceStack (reflection) -> JsonSerializer.DeserializeFromString
• SOAP Xml (manual mapping) -> Same SOAP client call as above with added mapping from DTO's to models

• JSON.Net (manual mapping) -> Mapping JSON to models directly using code based on The ZenCoder's code above, expanded to include mapping for the entire request (rooms and locations as well)

• ServiceStack (manual mapping) -> See the below code (based on example: https://github.com/ServiceStack/ServiceStack.Text/blob/master/tests/ServiceStack.Text.Tests/UseCases/CentroidTests.cs)

          var response = JsonObject.Parse(responseData).ConvertTo(x => new GetRoomListResponse()         {             Acknowledge = (AcknowledgeType)x.Get<int>("Acknowledge"),             Code = x.Get<int>("Code"),             Exception = x.Get("Exception"),             Message = x.Get("Message"),             RoomList = x.ArrayObjects("RoomList").ConvertAll<RoomModel>(y => new RoomModel()             {                 Id = y.Get<Guid>("Id"),                 Description = y.Get("Description"),                 Location = y.Object("Location").ConvertTo<LocationModel>(z => new LocationModel()                 {                     Id = z.Get<Guid>("Id"),                     Code = z.Get("Code"),                     Description = z.Get("Description"),                     Number = z.Get<int>("Number"),                 }),             }),         }); 

Notes / personal conclusions:

• Even reflection based deserialization is not that much slower than SOAP XML object generation in actual release mode (oops)
• Manual mapping in JSON.Net is faster than the auto mapping and it is very comparable in speed to SOAP Xml mapping performance and it offers a lot of freedom, which is great, especially when models and DTO's differ in places
• ServiceStack manual mapping is actually slower than their full reflection based mapping. I'm guessing this is because it's a higher level manual mapping than on the JSON.Net side, because some object generation seems to have already occurred there. Perhaps there are lower level alternatives on the ServiceStack side as well?
• All this was done with server / client code running on same machine. In separate client / server production environments, I'm sure the JSON solutions should beat SOAP XML because of much smaller messages that need to be sent over the network
• In this situation, JSON.Net auto mapping appears to be a tad faster than ServiceStack's for big responses.