I’m migrating from using a custom task runner for our app to Hangfire. The current implementation has the concept of tasks as a message and handler (ITask and ITaskHandler).
To keep this concept and avoid reworking a lot of code I have a small snippet to integrate Hangfire with Hangfire:
public void Execute(ITask task)
BackgroundJob.Enqueue<ImmediateTaskExecutor>(e => e.Execute(task));
The problem is one execution of the background task the argument is not actually created (passed to the ImmediateTaskExecutor as null). I believe this is because the runtime type is not stored with the argument, only the static type (e.g. ITask is stored in the database not TheTaskThatImplementsITask).
Is there a way around this for now and should this be considered a bug?
I would be very surprised if the runtime type was not properly serialized. I don’t recall if we have a similar case in our project (and can’t check now), but you can inspect the scheduled task in the dashboard and see the serialized argument - maybe that will give you some insight as to what’s going on.
@odinserj, I’ve just tried that but it results in an exception when the job is being run:
Type specified in JSON ‘System.Linq.Enumerable+WhereSelectArrayIterator`2[[System.Reflection.ParameterInfo, mscorlib, Version=184.108.40.206, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Type, mscorlib, Version=220.127.116.11, Culture=neutral, PublicKeyToken=b77a5c561934e089]], System.Core, Version=18.104.22.168, Culture=neutral, PublicKeyToken=b77a5c561934e089’ is not compatible with ‘System.Type, mscorlib, Version=22.214.171.124, Culture=neutral, PublicKeyToken=b77a5c561934e089’. Path ‘$type’, line 1, position 142.
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
at Hangfire.Common.JobHelper.FromJson[T](String value)
@odinserj I was using version 1.4.1 (the default version from Hangfire.Sample github, which I had assumed was the latest version).
Having upgraded to 1.4.5 that now fixes the exception posted. Perhaps the default should be to include the type names in the JSON being serialised? It pushes Hangfire a step further towards ‘just working’ without requiring any extra configuration. I don’t think my usage is particularly abnormal.
Or at a minimum perhaps somewhere in the documentation?
Many thanks for all your work! Looking forward to replacing our home-grown solution with something that actually works real nice