JSON Encoding issues

[fdmarc]

I've had two problems encoding C# objects into JSON with the Ably SDK.

First, when trying to encode a TokenRequest from IRestClient.Auth.CreateTokenRequestObjectAsync, by calling JSON.net in my HTTP controller. The call to JsonConvert.SerializeObject(tokenRequest) was returning JSON with the original field names from the TokenRequest class, and ignoring the JsonProperty attributes. So the resulting JSON had field names KeyName, Ttl rather than keyName, ttl, etc.

The issue seemed to be that version of JSON.net in my app was not able to understand the JsonProperty attributes from your SDK.

I solved this problem by calling the (deprecated) CreateTokenRequestAsync function, which returned the correct JSON (I can only guess as to who this worked).

The second issue that I hit was converting the other way - I was trying to send domain objects from my app as the payload of Ably messages. This time my JsonProperty attributes were being ignored. I solved this problem using this trick:

#92 (comment)

Do you have thoughts on how to address these problems?

If not, it would be nice to include this code snippet in the docs, since it's very powerful when you want to have fine-grained control over the JSON.

Thanks

[sync-by-unito]

➤ Automation for Jira commented:

The link to the corresponding Jira issue is https://ably.atlassian.net/browse/SDK-3809

[sacOO7]

@fdmarc sure we will most likely update the docs 👍 . Thanks for noticing : )

[sacOO7]

@fdmarc as you can see, I have created a PR to update README -> #1256.
Let me know if any other README updates are needed, thanks : )

[fdmarc]

I have a bit more information to help debug this. Here is a minimal repro from our codebase with the error message:

static class AblyExtensions
{
    public static Task<HttpPaginatedResponse> PublishAsync(this AblyRest ably)
    {
        var batch = JToken.Parse("{}");
        return ably.Request("POST", "/messages", null, batch, null);
    }
}

Produces this error:

AblyPublishRealTimeEvents.cs(127,60): Error CS1503 : Argument 4:
cannot convert from 'Newtonsoft.Json.Linq.JToken [C:\Users\User\.nuget\packages\newtonsoft.json\13.0.3\lib\net45\Newtonsoft.Json.dll]'
to 'Newtonsoft.Json.Linq.JToken [C:\Users\User\.nuget\packages\ably.io\1.2.12\lib\net46\IO.Ably.dll]'

[sacOO7]

@fdmarc got it 👍 .
I think it's better to send serialized strings externally. We will merge updated README soon 👍

[fdmarc]

That's not an option unfortunately - there is no Request method on AblyRest that takes a string, only JToken.

[sacOO7]

Understood. Your requirement is publishing multiple messages on multiple channels at the same time, right?
We will update request method to take payload as a string instead 👍
Meanwhile, you need to iterate over each channel to publish messages.

[fdmarc]

My immediate need is to send the same message to roughly 1-5 connected clients.

This is how I was approaching it:

    static class AblyExtensions
    {
        public static Task<HttpPaginatedResponse> PublishAsync(this AblyRest ably, IEnumerable<string> channels, IEnumerable<Message> messages)
        {
            JObject batch = new() { 
                { "channels", new JObject(channels) },
                { "messages", new JObject(messages) } 
            };
            return ably.Request("POST", "/messages", null, batch, null);
        }
    }

[sacOO7]

For the time being, you can do

    static class AblyExtensions
    {
        public static Task<HttpPaginatedResponse> PublishAsync(this AblyRest ably, IEnumerable<string> channels, IEnumerable<Message> messages)
        {
           for (var channelName in channels) {
            var restChannel = ably.Channels.Get(channelName);
            await restChannel.PublishAsync(messages);
           }
        }
    }

[fdmarc]

Yup, but I'm making the HTTP calls in in parallel:

            var message = new Message
            {
                Id = eventBase.FlipdishEventId.ToString(),
                Name = eventBase.EventName,
                Data = JsonConvert.SerializeObject(eventBase.GenericMapToPublicModel()),
                Encoding = "json",
            };

            // TODO:
            // https://github.com/ably/ably-dotnet/issues/1151
            // The Ably C# SDK does not support batch sending at present.
            var tasks = channels.Select(channel =>
                _restClient.Channels.Get(channel).PublishAsync(message));

            await Task.WhenAll(tasks);

[sacOO7]

I don't see it as a problem as long as the number of channels are limited ( ~10/12 channels).
If you have more channels ~100, you can use Parallel.ForEachAsync Method instead
There's a blog for this -> https://medium.com/@nayanava.de01/controlling-degree-of-parallelism-with-task-whenall-in-c-1ef1e9ff2bc

[sacOO7]

However, this should be a small change to be made from our side to the request method. I will check and create the PR soon 👍

[fdmarc]

Could you add an AblyRest.PublishAsync(channels, messages) function instead please? :) Then I don't need to concern myself with the lower level REST API.

[sacOO7]

It's not a part of standard ably public API specification : (
Though I will check and try to make a change that suits the requirement.

[sacOO7]

@fdmarc I have created a PR to fix your issue #1260. You can comment there if needed 👍

[sacOO7]

Closed via #1260.
@fdmarc you can open a new issue if there are JSON encoding issues in the future.

[sacOO7]

@fdmarc we have created a new release for this. Please use 1.2.14, you will find all fixes available there.