Cast Error when using DistributedCache

[monsieurberry]

Hi!

I'm just testing out the DistributedCache with SQL Server. I've created a Cache DB and table with ...

dotnet sql-cache create "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=DistCache;Integrated Security=True;" dbo TestCache

... and wired everything up in my Startup.cs by adding ...

services.AddDistributedSqlServerCache(options =>
{
options.ConnectionString = Configuration["DistCache_ConnectionString"];
options.SchemaName = "dbo";
options.TableName = "TestCache";
});
services.AddPiranhaDistributedCache();

.. to ConfigureServices(), and ...

App.CacheLevel = Piranha.Cache.CacheLevel.Full;

to Configure().

When I first load up my site everything works perfectly. I check my cache table and everything is in there, so I know writing to the cache works and all is (hopefully) configured OK.

When I refresh my page (now getting from the cache) I get the following error...

An unhandled exception occurred while processing the request.
InvalidCastException: Unable to cast object of type 'System.Collections.Generic.List`1[Piranha.Services.SiteService+SiteMapping]' to type 'System.String'.
Piranha.Cache.DistributedCache.Deserialize(byte[] bytes) in DistributedCache.cs, line 128

I've tried debugging and a few different options, however I'm a bit lost - was hoping I could try and figure out what was going wrong but no luck unfortunately.

I also tried out the same on 6.1.0 but I got the same error.

If you need anymore info please let me know.

Thanks!

[monsieurberry]

Managed to fix the issue with the following changes to Deserialize in DistributedCache.

A bit of a hack, but hopefully gives you guys an idea of where the problem is :-)

///

/// Deserializes the byte array to an object.
///

/// The byte array
/// The object type
/// The deserialized object
private T Deserialize(byte[] bytes)
{
if (bytes == null)
{
return default(T);
}
var formatter = new BinaryFormatter();
using (var stream = new MemoryStream(bytes))
{
var obj = formatter.Deserialize(stream);
if (!(obj.GetType() == typeof(string)) && IsSerializable(obj.GetType()))
{
return (T)obj;
}
else
{
// First lets decode the byte array into a string
var json = (string)obj;
// Next deserialize the json into an object
var settings = new JsonSerializerSettings
{
TypeNameHandling = TypeNameHandling.All
};
return JsonConvert.DeserializeObject(json, settings);
}
}
}

[tidyui]

Thanks for investigating the issue further! We'll take a look at it.

Regards

[monsieurberry]

Thank you, Håkan!

I think I may have found a better solution for you.

It seems as if the SiteMapping is cached as a List object, but when it's retrieved from the cache in SiteService, it specifies IList...

I was able to solve the issue by changing IList<SiteMapping> to List<SiteMapping> in GetByHostnameAsync.

Hope this helps :-)

[nahojd]

I get (more or less) the same error when I try to use RedisCache (from Microsoft.Extensions.Caching.StackExchangeRedis) or even the default Distributed Memory Cache (services.AddDistributedMemoryCache), which is just an in-memory implementation.

Specifically, I get

An exception of type 'System.InvalidCastException' occurred in System.Private.CoreLib.dll but was not handled in user code: 'Unable to cast object of type 'System.Collections.Generic.List`1[Piranha.Models.PostType]' to type 'System.String'.'
   at Piranha.Cache.DistributedCache.Deserialize[T](Byte[] bytes)
   at Piranha.Cache.DistributedCache.Get[T](String key)
   at Piranha.Services.PostTypeService.<GetTypes>d__8.MoveNext()

or sometimes in PageTypeService.GetTypes instead.

When i use RedisCache I can see that the data has been written to Redis, but it can't retrieve it.

Has anyone got DistributedCache working? I'm using the latest Piranha version (8.1.0).

[tidyui]

I will see if I can replicate the error on the version/v8.1 branch.

[tidyui]

So I have looked into the problem and apparently how models are loaded have changed a bit since the distributed cache was written. Also, unfortunately we don't run any integration tests on distributed cache, only on memory cache which I will look into, otherwise we would've caught the problem earlier.

For those of you that need distributed caching while we try to resolve the issue, I've created a gist that contains an alternate distributed cache that doesn't use binary formatting, instead it serializes objects using Newtonsoft.Json. This will not be as fast as using a binary formatter, but it's a good intermediate solution while waiting for the official fix.

https://gist.github.com/tidyui/95c441293af55f9eb906ba756ae398e5

Best regards

[nahojd]

@tidyui Thanks, I'll try that until this is sorted out! 👍