Monthly Archives: December 2014

What is GemStone? Part 2

A bit on GemStone history

When talking about Smalltalk, one of the advantages always mentioned is its “maturity”. In the previous post, I commented some GemStone features. If you read them carefully, it seems like if we were talking about a modern technology that couldn’t have been possible years ago. Wrong!!!!  GemStone Systems was funded in 1982 and I think the first release was a few years after. Of course, not all the features I commented exist back then, but nobody can discuss it’s history. That means that when using GemStone not only you will be getting the “maturity” of Smalltalk, but also it’s own maturity as an object database.

For a long time, GemStone was owned and developed by GemStone Systems. In 2010, VMWare acquired GemStone Systems. However, later on, in 2013, GemStone and all other Smalltalk products were acquired by a new company called GemTalk Systems. I don’t know all the details (if you want, you can check them online)… but what I think that matters most is the fact that now GemTalk Systems has all GemStone engineers working, it does not depend on higher companies decisions (like VMWare) and is 100% focused in Smalltalk!

If you want to have a look at a general overview of the company and the impact of their products, I recommend the slides of this presentation.

Why GemStone is even more interesting now than before?

Just in case… I will clarify again: in these posts, I always give my opinion. Not everybody should agree with me.

Let’s go back some years ago. At that time, a few things happened:

  1.  Most of the developed apps were fat desktop and GemStone did not have a UI nor an IDE to develop.
  2. There was no good open-source and business friendly Smalltalk (I said it was my opinion!).
  3. GemStone did not have a free license.

The above things meant that someone developing a fat client app would require two Smalltalks: one for the UI and GemStone as the database. That also meant paying two licenses, one for the commercial Smalltalk for the UI and one for GemStone. And that could have been expensive for certain uses. However, things have changed in the recent years:

  1. Most apps are now web based so we do not need a fat UI.
  2. There is a very cool open-source and business friendly Smalltalk: Pharo.
  3. Gemstone does offer a free license with generous limits (in future posts, I will explain better the limits).

That means that you can develop a whole web app in Pharo, put the code in Gemstone and run it from there. And… paying no license (with GemStone free license limits). This is why I think GemStone is even more interesting now than it was ever before.

A bit more about fat client vs web based

When using an app with fat client and GemStone as object database, we actually have two Smalltalk communicating with each other. It is not like “I develop in Smalltalk Whatever and I deploy in GemStone”. No… it is both, Smalltalk Whatever and GemStone running and each of them is communicating to each other. This means there must be some connection or some kind of mapping/adaptor between the two, because both can have some differences in the kernel classes. This kind of software is what GemTalks Systems sells as “GemBuilder”. So we have “GemBuilder for VisualWorks” and “GemBuilder for VisualAge” etc… I have never used these products so I can’t talk much about them.

Just a last comment. Of course, building a GemBuilder for a Smalltalk dialect seems “easy” in the sense that GemStone is also a Smalltalk. But what if there were GemBuilders for other languages so that these can use GemStone as the object database?  Well, there is also a “GemBuilder for Java“. This tell us a little about the internal GemStone architecture (the object repository process is a bit decoupled from the VirtualMachines running the language). But we will see this later.

What do people mean by “Develop in Pharo and deploy in GemStone”

In a very first step, an app could be both developed and deployed in Pharo. That means we use Pharo tools to develop it and we also use Pharo to run our application in production. This may work well enough for small apps or a prototype. But, at some point, we may need more power. As I discussed in the previous post, there are many alternatives. Not all solutions are available for all situations. The solution I am interested in this post is to directly run (deploy) your app in GemStone. Which are the requirements? The app cannot be fat client (in Pharo, this means the app should not be a Morphic app). It could be either a web app or a rest server or whatever form that doesn’t involve a fat UI.

In fact… I guess you could even use GemStone as your backend language and database and provide a REST api answering JSON or whatever to a mobile app (maybe even using Amber??? I don’t know…).

With this alternative, the idea is to develop in Pharo. Then… we simply load our code (using Metacello, Git, Monticello, whatever) into GemStone and we run it there. Hence, “develop in Pharo and deploy in GemStone”. Of course… all the code we have developed in Pharo may not work perfectly in Gemstone or it may behave a little bit different. So some adjustments and work will likely must be done when making the app to work in GemStone besides Pharo. But we will talk about this in a future post.

Most of the times, the app continues to be able to be run by Pharo (besides developing with it). So you can likely continue to develop, run, test and debug your app locally with Pharo. And then periodically you deploy and test it in GemStone.

To sum up

I hope I have clarified a bit the different scenarios when using GemStone and what people mean when they say “develop in Pharo and deploy in GemStone”. All my posts from now onward will take this scenario in mind.

See you soon,

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What is GemStone?

What is GemStone

When you ask a Smalltalker what Smalltalk is, you will find many different answers: a language, an environment, an object system, a platform or simply a combination of all of those or more. With GemStone, I have a similar feeling. I think different people will answer differently. To me, GemStone is an object system with two big concepts included: an object database and a language. Others will say that it’s a transactional or persistent Smalltalk, an object database, etc.

Before continuing, let me clarify a few things for this post and all the posts I will write after this one:
– I will not be discussing here relational databases vs object databases vs NoSQL. That’s a whole other discussion that I am not willing to write about right now.
– These posts are aimed mostly for Smalltalkers and GemStone newbies, but not for GemStone experts.

Ok…that being clarify…let’s start. When I refer to an object database, I mean exactly that: an Object Database Management System. Rather than dealing with tables as in relational databases, we can directly persist and query objects. Most of the OODB I have seen in other languages, are kind of an external piece of software that is only a database (just as relational databases are). For the moment, just imagine any of the relational databases you know but storing objects instead. In this case, you still need a language (and probably a VM running that language) for your application logic and you still must communicate to the database to perform the storage and retrieval of objects. I know… that should already be easier than dealing with relational databases but I personally think it could be better.

GemStone goes a step forward. What if the “database” would also include the language to run your application? Sounds cool, doesn’t it? So, this is the second concept GemStone has: it’s also a language implementation in itself. And which language? Smalltalk, of course!!! This means GemStone IS a Smalltalk dialect, just as any other dialect like Pharo, Visual Works, VisualAge, etc. So… GemStone is a Smalltalk dialect but also acts as an object database. You might be thinking “any Smalltalk can act as an object database because we have image persistency”. Fair enough. However, image persistency lacks lots of needed features to be a really scalable database (we will talk about this in other posts).

GemStone analogy to an image-based Smalltalk

As I said, the aim of these posts is to explain GemStone in a way that most readers can get it. And sometimes a good way to do so is by making a comparison to what we already know. So… let’s take an example with Pharo. Say we have one application running in one image. Soon, one image can start to be too little power and we need to scale. Smalltalk is cool and allow us to run the very same image with N number of VMs. Ok… so now we have 10 VMs running our app. Imagine this app needs persistency (as most apps do). If the database is outside Pharo (say a relational DB, NoSQL, etc), then we have no problem since the access to the database from multiple images will be correctly synchronized. But would you be allowed to use image persistency in this scenario? Of course not, because it’s not synchronized among all the VMs. But hell… that would be nice, wouldn’t it?

GemStone offers exactly what I would like: multiple (hundreds) Smalltalk VMs running and sharing the same “image” (repository/database of objects) in a synchronized fashion.

Note, however, that GemStone does NOT have a UI (it is headless) nor development tools (no IDE). So you still need another Smalltalk to develop your app code. And this is why the Pharo / GemStone combination is so great. But I will talk about this in another post.

To sum up

So you are the happiest programmer on the block. Your language has closures (have you ever try to imagine not using closures again???), an amazingly simple syntax, a small learning curve, decades of maturity, serious open-source and free dialects available, etc. Now I tell you can literally run hundreds of Smalltalk VMs all sharing the same repository of objects. But not only that… also imagine not having to write a simple mapping to SQL. Imagine that saving an object in the database is just adding an object to a collection (“clientList add: aClient”) and a query as a normal select (“clientList select: [:each | each age = 42 ]”). BTW… Did someone notice that, apart from selecting via an instance variable (‘age’ in this example), I can also send other domain specific messages? Say…. “clientList select: [:each | each associatedBankPollicy = BankPolicy strict ]”.

Ok, you might still not be convinced. What if I also tell you GemStone supports:

  • Multiple-user database support
  •  Indexes and reduce conflict Collection classes
  • Distributed env (imagine that your hundred VMs can also be running in different nodes!
  • Fault tolerance
  • Security at different levels (even at object level)
  • 64 bits VMs and multi-cpu VMs
  • Free license with generous limits

Ok…too much info for today. As you can note, I am very happy with these technologies so I will try to be objective… but I cannot promise you anything hahaha! I hope I have provoked and intrigued you enough to read on the future posts.

Stay tuned,


My presentations at “Summer School on Languages and Applications”, Bolivia 2014

A few months ago, I was invited to give some talks at “Summer School on Languages and Applications” in Bolivia. I offered several topics I was able to talk about and 3 of them were chosen. The target of the presentations were mostly university students who haven’t seen Smalltalk never before. So my presentations tried to be as friendly as possible for that public.

The presentations were:

Web Development with Smalltalk: This talk was actually mostly about Seaside, but I also gave a very short intro to Smalltalk and, at the end, showed a bit of Amber. Besides the slides, I showed some simple demos. In addition, at the end of the talk, I showed  the financial commercial application we are developing for a client and a video about the great Yesplan.

Smalltalk and Business:  I gave a quick overview of the Smalltalk advantages but from the enterprise point of view. I also talked quite a bit about Pharo (and why a strong open source dialect would matter), its Association and Consortium and all community related stuff. Finally, I explained a little bit about GemStone and Seaside and how the combination of all that ends on what is the stack of frameworks I enjoy the most these days.

Marea: Application-Level Virtual Memory for Object-Oriented Systems: This talk was very similar to the one of my PhD defense… but I tried to explain it a bit simpler (and I removed/skipped some slides).

The general feedback I received was positive and what I found is that most of the people were surprised that one could do web apps and real business with Smalltalk. Most students seem curious and wanting to learn more.

Everybody treat us very well. Everywhere.  In the street, in a restaurant, in the university, in the hotel, etc. The people were very gentle and respectful. We even had time to do some tourism:

visit to Saint Peter Hill

So…. in general, it was a very good experience and I really enjoyed my time there.


Reviving my blog

Almost 2 years ago, I wrote my last post. What has happened since then that I didn’t write again? Nothing strange. Typical excuses… too much work and little time for writing blogs, contributing to open-source projects, actively participating  in mailing lists, etc.

Since I have finished my PhD two years ago, I have been working as an independent software developer. I had the pleasure of being 100% busy with different projects all in Smalltalk. I really can’t complain. I do have some free time now so I will try to revive this blog that I have always enjoyed a lot.

What I will be writing about? Most of my topics used to be about low-level stuff: some about Virtual Machine, some about meta-programming, frameworks, Smalltalk deep and internal details, my PhD topic, etc. But what I will be writing now? Well… my context has changed a bit. While I do still develop some internal frameworks, libraries or low-level code, I am mostly dealing with normal business developments, persistency issues, web development (Seaside, jQuery, Bootstrap, Ajax, etc), Pharo, GemStone, deploy and configuration, security, sysadmin, etc. So I guess my posts will be likely related to that.

Years ago, I wrote a long series of posts I called “Journey through the Pharo Virtual Machine” which was intended to VM newbies. I personally think that those posts contributed a bit to the huge work from the Pharo team to ease the compiling and building of the Pharo VM (mostly for none VM hackers). That made a lot of progress in the VM field. Now, it is very common to read in the Pharo mailing list about people who easily compiled the VM or fixed a bug or did a port to platform X or whatever… So I think we are now seeing the fruits of a long effort that started years ago by a lot of people.

Something that is in my head these days is to do a similar series of posts but about GemStone Smalltalk. In the same way I was not an expert in the VM field when I wrote the previous series of posts, I am not either a GemStone expert. There are people with much more knowledge than me. However, I feel I have a few things to share and that some other people would like to be aware of. So….what do you think?  Would you be interested?

Ok…this was all for today. I really hope I can revive this blog and start writing again which I have always enjoyed.

Bye,