Getting being delete variant codes

I got the question here Content Events and Service API | Optimizely Developer Community , and CHKN contacted Optimizely developer support service which is the good/right thing to do. However it could be beneficial for a wider audience, hence this blogpost.

If you are developing new Optimizely Commerce Cloud now, you should be using the latest version (CMS 12/ Commerce 14), or at least Commerce 13.31 if you have to stay with .NET 4.8. You then could use the IContentEvents to listen to any events that might be fired from Service API.

However, if you are using older versions, you might be limited to lower level, non content event through EventContext. It works, but with a catch: there is no EntryDeleting event in EventContext. At this point I’m not entirely sure why, probably just an overlook. But it’s not impossible to work around that issue.

As I suggested in the post, EntryUpdating is like a blanket event – every change to the entries goes through there. The sender is a CatalogEntryDto, which should contain information about the being deleted entries.

        private void Instance_EntryUpdating(object sender, Mediachase.Commerce.Catalog.Events.EntryEventArgs e)
        {
            var dto = sender as CatalogEntryDto;
            if (dto != null)
            {
                var rows = dto.CatalogEntry.Where(x => x.RowState == DataRowState.Deleted);
                var deletingCodes = rows.Select(x => (string)x["Code", DataRowVersion.Original]);
                //do stuffs with codes being deleted.
            }
        }

And then to listen to the event in one of your IInitializationModule

EventContext.Instance.EntryUpdating += Instance_EntryUpdating;

However, there is a caveat here: as EntryUpdating happens before the entry deletion, it is possible that the change did not go through (i.e. the changes were to be reverted). It is unlikely, but it’s a possibility. You might accept that, or you can:

  • Store the id and code in a “Deleting entry” dictionary
  • Listen to EntryDeleted event and match from DeletedEntryEventArgs parameter (which contains EntryId ) to get the deleted Code, and continue from there.

The hidden gotcha with IObjectInstanceCache

It’s not a secret that cache is one of the most, if not the most, important factors to their website performance. Yes cache is great, and if you are using Optimizely Content/Commerce Cloud, you should be using ISynchronizedObjectInstanceCache to cache your objects whenever possible.

But caching is not easy. Or rather, the cache invalidation is not easy.

To ensure that you have effective caching strategy, it’s important that you have cache dependencies, i.e. In principles, there are two types of dependencies:

  • Master keys. This is to control a entire cache “segment”. For example, you could have one master key for the prices. If you needs to invalidate the entire price cache, just remove the master key and you’re done.
  • Dependency keys. This is to tell cache system that your cache item depends on this or that object. If this or that object is invalidated, your cache item will be invalidated automatically. This is particularly useful if you do not control this or that object.

ISynchronizedObjectInstanceCache allows you to control the cache dependencies by CacheEvictionPolicy . There are a few ways to construct an instance of CacheEvictionPolicy, from if the cache expiration will be absolute (i.e. it will be invalidated after a fixed amount of time), or sliding (i.e. if it is accessed, its expiration will be renewed), to if your cache will be dependent on one or more master keys, and/or one or more dependency keys, like this

   
        /// <summary>
        /// Initializes a new instance of the <see cref="CacheEvictionPolicy"/> class.
        /// </summary>
        /// <param name="cacheKeys">The dependencies to other cached items, idetified by their keys.</param>
        public CacheEvictionPolicy(IEnumerable<string> cacheKeys)

        /// <summary>
        /// Initializes a new instance of the <see cref="CacheEvictionPolicy"/> class.
        /// </summary>
        /// <param name="cacheKeys">The dependencies to other cached items, idetified by their keys.</param>
        /// <param name="masterKeys">The master keys that we depend upon.</param>
        public CacheEvictionPolicy(IEnumerable<string> cacheKeys, IEnumerable<string> masterKeys)

The constructors that takes master keys and dependency keys look pretty the same, but there is an important difference/caveat here: if there is no dependency key already existing in cache, the cache item you are inserting will be invalidated (i.e. removed from cache) immediately. (For master keys, the framework will automatically add an empty object (if none existed) for you.)

That will be some unpleasant surprise – everything seems to be working fine, no error whatsoever. But, if you look closely, your code seems to be hitting database more than it should. But other than that, your website performance is silently suffering (sometimes, not “silently”)

This is an easy mistake to make – I did once myself (albeit long ago) in an important catalog content cache path. And I saw some very experienced developers made the same mistake as well (At this point you might wonder if the API itself is to blame)

Take away:

  • Make sure you are using the right constructor when you construct an instance of CacheEvictionPolicy . Are you sure that the cache keys you are going to depend on, actually exist?

In newer version of CMS, there would be a warning in log if the cache is invalidated immediately, however, it could be missed, unless you are actively looking for it.

Note that this behavior is the same with ISynchronizedObjectInstanceCache as it extends IObjectInstanceCache.

Announcing Pro Optimizely Commerce Cloud

Yes, you guess it right, it’s a(nother) book

It has been 5 years since I started Pro Episerver Commerce back in early 2016. The book was a success, not as big as I hoped for, but definitely bigger than I expected. Tackling a niche market, it was fairly popular within the community, and it gave me a lot of happiness (and some pocket changes) to see that it helped many developers to understand and use the framework – which I help created, and love – better.

So much has changed in the last 5 years.

I have my first kid, and a second one. I left Commerce development team, to work on my own, then have a small team. Episerver bought Optimizely, then rebrand.

And so much more has happened with Episerver Commerce, more than just being renamed to Optimizely Commerce Cloud.

It deserves a new book!

To celebrate my 10th anniversary with Episerver (now Optimizely), I am proud, and excited to announce the second edition of Pro Episerver Commerce – Pro Optimizely Commerce Cloud. Most of the content written in Pro Episerver Commerce is still very much applicable, but I feel there is a need to refocus and expand on important parts.

You can register your interests today at https://leanpub.com/prooptimizelycommercecloud

Purchasers of Pro Episerver Commerce – even if you obtained the free version – will receive a 40% discount code for the new book – so don’t miss it.

I will see you there!