What happens when you throw an exception inside the GetOrSetAsync Factory ?

[Samirasimha]

var data = fusionCache.GetOrSetAsync<NakamirOrganizationEntity>(
			key: $"OrgStorage:{organizationId}",
			factory: async (ctx, t) =>
			{
				var org = GetOrg();
				return org ?? throw new InvalidOperationException($"Organization '{organizationId}' not found.");
			},
			tags: [$"OrgStorage:{organizationId}"],
			token: token);

In this case if the GetOrg fails for whatever reason and an exception is thrown,
What gets set in the cache ?
Will the exception be cached or nothing gets cached at all ?
What will data hold ?

Any tips on best practices on handling this situation while using Fusion Cache ?

[jodydonetti]

Hi @Samirasimha

var data = fusionCache.GetOrSetAsync<NakamirOrganizationEntity>(
			key: $"OrgStorage:{organizationId}",
			factory: async (ctx, t) =>
			{
				var org = GetOrg();
				return org ?? throw new InvalidOperationException($"Organization '{organizationId}' not found.");
			},
			tags: [$"OrgStorage:{organizationId}"],
			token: token);

In this case if the GetOrg fails for whatever reason and an exception is thrown, What gets set in the cache?
Will the exception be cached or nothing gets cached at all ? What will data hold ?

Short answer

Nothing, because the factory did not in fact produce any value.

Longer answer

See above, but also: if you enabled Fail-Safe, it depends.

Basically, when the exception is thrown:

• if there was already something in the cache (expired) -> it will be re-saved temporarily
• if there was nothing in the cache already -> either the exception is thrown or the failSafeDefaultValue param will be used, if specified

Any tips on best practices on handling this situation while using Fusion Cache ?

Sure thing, if you take a look at the Fail-Safe docs I linked above, that would be the best way to deal with transient issues (meaning: temporary problems with your datasource (database/service/etc).

On top of handling exceptions when calling GetOrg() (from your example), you may be also interested in handling temporary slow responses from that same GetOrg() method.

To do that, you can take a look at Factory Timeouts.

Finally, if you want to have an overview of all the main features of FusionCache and what they can bring you, also in terms of before/after numbers, you can take a look at the Step By Step.

It's a bit long, so maybe bring a cup of coffee/tea 😅

Hope this helps.