Month: April 2016

Articles software developers should read, at least once

… if not twice.

These days, almost every software developer has a blog – so it’s sh*tloads of content around the Internet. Truth is, the good, accurate, long-lasting contents are hard to be found. Most contents are supposed to be obsolete very soon – and it’s OK, because many contents are for a very specific situation in a very specific time. But can we have a collection of the precious contents that are useful not only today, this week, this month, but ten years from now?

This is supposed to be a definitive collection of great contents that will be helpful for your entire career as a software developer. It’ll be updated frequently, with new link as I found it.

The Log: What every software engineer should know about real-time data’s unifying abstraction (Jay Kreps)

Logging is essential to every serious software system. But it’s not easy – getting it right can be indeed hard, especially in real-time. This article provides a deep knowledge about the concept.

http://engineering.linkedin.com/distributed-systems/log-what-every-software-engineer-should-know-about-real-time-datas-unifying

The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (Joel Spolsky)

It’s been 26 years since Unicode was introduced and still, not all people can get it right. This article gives you – as the tittle suggests – a minimum knowledge about Unicode, and how to not get it wrong.

http://www.joelonsoftware.com/articles/Unicode.html

What Every Programmer Should Know About Memory (PDF) (Ulrich Drepper)

This is a pretty low-level paper, you will learn about how memory works at hardware level. Still interesting and useful. Who knows someday you’ll have to get your hands dirty with some memory stuffs?

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Hiring process might suck, and how to fix it

I recently read this post F*** You, I Quit — Hiring Is Broken
and found it interesting. If you have time – read it (and of course you should have, because this blog is far less famous than medium.com – the combination of page views for post in this blog is very likely to be much smaller than that single post).

I feel bad for the author for being in such situation – getting rejected 5 times in a row, is a hard thing to swallow. Especially when he is considered famous in developer’s world/ and has big passion in coding. And it’s not the first time, we hear someone rants about the hiring process, and it’s very unlikely to be the last. Let’s agree that the hiring process for developers might suck.

But then, it’s the way it works.

The first time no offer given, it’s probably their fault. The second time no offer given, it’s probably a bad luck. The third time no offer given, it’s probably your fault.

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The quirks of coupons

If you have been using the promotion system in Episerver Commerce (or should I call it “old promotion system” – the “new promotion system” is almost out of BETA and it will soon be the promotion system), you should know about the coupon – which is an option setting for a promotion. When it is set, the customers will be required to input that special code in order to get the reward, even if their carts fulfilled all other requirements (the subtotal, the lineitems, the shipping method etc.)

The coupon in old promotion system is quite basic – you can set only one per promotion, or nothing at all. Advanced scenarios like customer-specific coupons (there are multiple coupons and each of them is valid for only one customer) are not supported. (This is one of reasons why you should consider to move to new promotion system ASAP). You can use redemption limits in combination to specify how many times a coupon can be used. But in this post we will talk about the quirks of storing it.

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Upgrade your website to Commerce 9

You know what – Commerce 9 is released. OK, I’m just kidding, it was released 6 months ago, in October 2015. Last week, Commerce 9.12 was released, and at this time of writing, Commerce 9.13 is on the oven just released. So it’s not so new – but with 6 months on the field, I think Commerce 9 has proven it’s stable and production-ready to be your next version. If you are looking for an upgrade to your website, Commerce 9 is the obvious choice. Many customers have successfully upgraded their sites to Commerce 9 – and the results have been very encouraging.

But it does not mean that upgrading is easy. Commerce 9 is undoubtedly a big upgrade, and getting there is not just an easy walk. So how to ensure a successful upgrade?

Plan ahead:

The catalog subsystem was rewritten almost entirely in Commerce 9, resulting in some very big migration steps. Depends on the size of your catalog, it can take from a couple of minutes, to hours (I would not be too surprised if it takes a day). So plan for the possible down time (even though in most cases you will be upgrading your site in staging first).

Commerce 9 is also a major release, so there were breaking changes – you will have to fix some of your code, to make it compiled. The amount of code that actually broken should be small, but it’s better if you check this list http://world.episerver.com/documentation/Items/Upgrading/EPiserver-Commerce/9/breaking-changes/ to see how much works you’ll need (tips: the less you use “internal stuffs”, the code you’ll have to change. The internal stuffs are, by convention, marked with special doc tag.).

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Understand the retry policies in Episerver

This is pretty internal stuffs – you will almost never use it yourself (you technically can, but there is no guarantee of backward compatibility whatsoever). I learned the stuff recently and found it interesting enough to share.

No matter how powerful your server(s) are, and how reliable SQL Server is, there are chances that a query can result in error. Hell, there are bunches of error codes that can be returned (and I never remember one, Google made a pretty bad habit of forgetting everything). But they can be divided into two categories:

  • The un-retry-able errors, such as a grammar error in your stored procedure, or a parameter is missing, or mismatch. These errors need human-interaction to correct them before continuing.
  • The retry-able errors, which means if you re-run the query, there is a chance that it would eventually succeed. Compared to the un-retry-able errors, these are in smaller number. A deadlock can be considered as retry-able (with the hope that the deadlock conditions are no longer present, the other threads finished their works and released the locks). A timeout error can be considered as retry-able (with the hope that the server can run the query faster, this time). In the end, your query can succeed, after some tries.

You might ask, why retry? The question is, why not? Retrying the query can make it works, and as it’s transparent from end-users perspective, it might provide a smoother experience for them. Say, they are trying to place an order. Because of your highly successful campaign, there are a lot of customers trying to do the same thing at the same time, resulting in some occasionally deadlocks. You’ll be much happy to silently retry and have another order in place, than showing “Something went wrong” to the customers. Of course, the previous errors will still be logged for further analytic, but you’re good for now.

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Episerver Commerce SearchProvider – demystifying

This post is an excerpt from my book, but it’s the short one. It looks like there is a confusion of where the searchprovider is used in Commerce

Many important features in Commerce Manager use index-based search provider to search for entries – it’s simply faster and more flexible to work with. They might not be truly “real-time”, but they’re close (with the right configuration). The only drawbacks are they require extra processing (for indexing entries), external files/configurations, but the advantages easily overweight any of those drawbacks.

There are three search providers provided by Episerver Commerce: LuceneSearchProvider, Solr35SearchProvider, and FindSearchProvider (four if you count SolrSearchProvider as well). LuceneSearchProvider comes as the default option with EPiServer.Commerce.Core, and it’s the only one does not require extra configurations.

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UX design lessons – from a metro perspective

When I come to a new city, I usually pay close attentions to its metro system. Of course, it rarely shows up in TripAdvisor as an attraction of the city, but for me, it’s not only a necessity (based on a quite tight budget, public transportation is almost always our first choice), but also can tell a lot more about the history of the city, the people and the daily life here.

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New York metro system . Make sure you don’t look at the rails.

I’m not a traveler myself, I have visited only Rome, Paris,  Venice, Florence London, San Francisco and New York, and of course Stockholm – where I am living. Venice and Florence have no metro I’d know of, and I only tried BART (Bay area rapid transport) in San Francisco, so only metro systems in remaining cities count. In those five, I know Stockholm metro system (tunelbanna) the best, and like it the most, so this post can be highly biased opinion. If I did misunderstand a metro system, kindly point it own.

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Import catalog: beware of warning messages

Recently I worked with a support case from a customer. They complained that the catalog import is too slow for them, it took them 6-7 minutes to import 200 entries. Their catalog is about 50k entries, which is not particularly big, but not small neither, and with that rate, it does mean they will have to wait for days for the catalog imported. This is of course not good and I jumped in when I became available. (In the end, I like performance tuning so much that I find it hard to refuse a case like this)

I did try to import their catalog on my development machine – a relatively powerful desktop with Intel Core i7 4790 CPU, 16GB of RAM and 256GB SSD on Windows 10/.NET 4.5.2. Everything went quite well – I achieved a rate of 200 entries per 9-10 seconds, which is, IMO, more than enough. (And this is on Commerce 9, on Commerce 8 then I would suspect it’s 3-4 times slower).

After some conversations with Episerver’s developer support team, it seems that the slowdown only happens with the re-import. I tried it again with re-import. Hmm, something is wrong here. The import is much slower and it eventually stops at some points. The debugger shows that it starts quite well, even faster than a new import (200 entries per 3-4 seconds, a very recent version of Commerce made an improvement of skipping the entries which are not changed to speed up the import), but it slows down by time. Profiling does not show anything obvious, most of the time was spent with loading the MetaObject:s – which is kind of expected.

I was starring at the import tab, and wondering what can be wrong, and suddenly I realized the answer is what I was looking at:

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What not to do with your login/register page

This post is strictly my personal opinions, it does not represent my employer’s views in any way.

Login/register page is essential to any site, especially any Commerce site. You should always follow the proven, established practices, but yet many sites still have issues with their login and register page. Make sure that you do not do anything mentioned below:

  • Use HTTP for login/register page.

You might say “What?”. It’s 2016 already and certificate is cheap as hell (even free, if you count Letsencrypt). Still, there are Commerce sites use HTTP for login/register. This, sadly, happens to one of my favorite sites, itsajten:NonHttps (1)

In case of itsajten, there is not much of sensitive information an attacker can get if he sniffs the network and gets my password. I’m in Sweden and almost everything is transparent, even my income. But still, it does mean that I’m subject to social engineering attack. I notified itsajten about this but never heard from them since – which is a pity. They are otherwise very nice and they offer some of the best prices on the item I interested.

 
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