Tag Archives: Tanker

“New” Tanker – current status

Both ESUG 2012 and GSoC have finished. At ESUG I gave a presentation about Fuel/Tanker (sorry, no slides because it was all demo). I also presented Tanker in the ESUG Awards….we got the 4th place, and only 8 points of difference with the 3er place ūüôā ¬† Anyway…I wanted to make public what exactly we finally managed to do with Tanker, a package exporter and importer that uses Fuel serializer. As I said in a previous post, we have changed a lot how Tanker works internally. In that post also I mentioned that Tanker didn’t support source code export/import, but in this new version, it does support methods source code, class comments, timestamps and everything that is currently being stored in the .changes or .sources file.

Exporting packages

The following figure shows how the export works. The input is a package of code (classes + extension methods), in this example “MyPackage”. The first step is to traverse the classes and methods of the package and do 2 things: a) write the source code (source of methods, class comments, timestamps, etc) to a text-based chunk format sources file (MyPackage.tankst); b) create “definition” objects. These objects represent a kind of object model that store all the necessary information of the code entities to be able to recreate them back ¬†in another image. So we have for example, TAClass, TATrait, TAMethod, TABinding, TAAdditionalMethodState, TATraitAlias, TATraitComposition, etc…

Something key here is that besides all that information, we also store the relative position of the source code of the¬†entity¬†in the “MyPackage.tankst”. So for example, TAMethod instances will have a number representing that relative offset (similar to the pointer that CompiledMethods have in their trailer to .sources/.changes) where its source code is.

Another important detail is that in TAMethod we are storing the bytecodes, because even if we have the source code we want to avoid needing to compile during the import.

Once we have finished writing the sources file and creating the definitions, we just serialize them into a Fuel binary, say “MyPackage.tank”.

Importing packages

The following diagram shows how the import works. The input is the sources file (MyPackage.tankst) and the Fuel binary file (MyPackage.tank). The first step is basically to read the sources file and append all its contents in the .changes file (so that to get the same behavior as if we were installing a package with Monticello). But before doing that, we temporally store/keep the current “end” position of the .changes file ūüėČ ¬†(you already guessed why?).

The second step is to materialize the definitions using Fuel. Something very nice is that the definitions that were serialized, also understand the necessary messages to be installed in the system (#installUsing: aSourcesFile environment: anEnvironment). So we basically tell each class and each extension method to get installed in the system. Those objects will delegate to the rest of the definitions to complete their task (all definitions know what to do when installing them in the system).

Classes and traits will use the class builder to recreate¬†themselves¬†back. The source code was already installed in the .changes, so now we need to fix the “pointers” from our newly created classes/methods to point to the correct place of their source in the .changes file. And this is very easy because their position is just the “end” position of the .changes before installing our package (that value I told you we were temporally storing) + the relative position that was stored in the definition itself ūüôā

So what is the biggest difference with Monticello for example? The key point is that we export bytecodes and we avoid having to compile during import. This make things faster while also being able to install packages without compiler (very useful for bootstrapping for example).

How to install it and use it

Tanker only works in Pharo 2.0 (because we rely on new class builder and layouts) so you first need to grab an image. Then, you can evaluate:

Gofer it
smalltalkhubUser: 'marianopeck' project: 'Tanker';
package: 'ConfigurationOfTanker';
(Smalltalk at: #ConfigurationOfTanker) perform: #loadDevelopment.
Yes, so far there isn’t a stable version yet, we are waiting for new class builder.¬†Be careful because that will install the new class builder (and change the system to use it) ¬†and it may have some bugs…so take care ūüôā
The export and import look like:
aPackage := TAPackage behaviors: {MyClass. MySecondClass} extensionMethods: {String>>#myExtensionMethod1. Object>>#myExtensionMethod2}.
 package: aPackage
 binariesOn: aBinaryWriteStream
 sourcesOn: aTextSourcesWriteStream)

 binariesFrom: aBinaryReadStream
 sourcesFrom: aSourcesReadStream)

However, we do not expect the final user to provide all the list of classes and extension methods. Therefore, we have helper methods to export and import RPackages and PackageInfos. Example:

 TAExport exportRPackageNamed: 'MyProjectCore'.
 TAExport exportRPackageNamed: 'MyProjectTests'.

TAImport importPackageNamed: 'MyProjectCore'.
 TAImport importPackageNamed: 'MyProjectTests'.


So that was all for today. Probably, I will do another blog post where I will show how we can query Metacello to know which packages to export and in which order, some details about the new class builder, some benchmarks while exporting all seaside/pier/magritte (10 seconds to export and 20 to import), and so on. The conclusion we got with this project is that indeed Fuel can be successfully used in yet another completely different domain. If you want to help us, please test it with your own packages. Right now we have only one open issue (need to recompile if superclasses present in the image have reshaped). I guess that soon we will fix this last issue and release the first stable version. In the future we plan to analyze how can we really integrate Tanker with Monticello/Metacello.

Tanker screencast and image ready for testing

Hi guys. Last days, we submitted Tanker to the ESUG Innovation Technology Awards. As part of that submission, I have created a screencast and an image with the examples.

The screencast gives you an introduction to Tanker and shows you how to export and import packages.¬†I starts with a simple example, then it exports a real library and ends up exporting all Seaside, Magritte and Pier ūüôā ¬† Ahhh yes, sorry for my voice, I know it is ugly hahaha. You can also watch it here:

You can also get the image I used for the screencast, which you can try and experiment.

Have fun,

Tanker: transporting packages with Fuel

Hi all. You may have noticed that Tanker is starting to appear in some mails or in the Pharo issue tracker. Tanker is a project that Martin and I have been developing for a while and we are going to submit it this year to ESUG Innovation Technology Award. Therefore, I thought it would be interesting to explaining what it is, its current status, its goals, etc.

What is “Tanker” and what was “FuelPackageLoader”?

Right now the common way to export and import packages in Pharo is by using Monticello (or doing fileOut, which is almost the same). This ends up exporting the source code and then compiling it during the import.¬†Tanker is a tool to export and import packages of code in a binary way using¬†Fuel serializer. Using Fuel enables us to¬†avoid having to compile from sources during the import. Tanker¬†understands¬†the concept of “packages of code” and the correct integration of them into the system. For example, it initializes classes, sends notifications, etc.

Tanker was first a prototype called “FuelPackageLoader” which was what I used for the¬†example of exporting and importing seaside packages.¬†In the last months, we have renamed the project to “Tanker”. Why? Because we do not want people to think that it is a Fuel project. In fact, Tanker is a simple USER of Fuel. Just as any other code that uses Fuel. This is why we have also moved it to its own repository.

Fuel has a package called “FuelMetalevel”.¬†This package gives Fuel the knowledge of how to correctly serialize and materialize classes, metaclasses, traits, method dictionaries, compiled methods and closures, in other words, all the entities related to code and runtime infrastructure. It only knows how to serialize and materialize correctly. Nothing else. It does not initialize classes, it does not notify the system about the materialized classes, it does not install classes in Smalltalk globals, etc.

Current features, design and missing things

Right now, Tanker provides the following features:

  • It is able to export a package to a .tank file and import it in another image. The input for the export is a TAPackage which basically contains a list of classes and a list of extension methods. We are¬†completely¬†decoupled from the “package representation” (PackageInfo, RPackage, MCPackage, etc). However, we provide an API if you want to directly export from those types of packages.
  • Classes are initialized and installed in Smalltalk globals, events are sent, etc.
  • It has the ability to add additional user-defined objects to the package being exported (this is used, for example, for the Pharo generation from a kernel to store large/heavy class variables, tables and fonts).
  • It supports pre and post load actions represented as closures.

From the design point of view, Tanker:

  • Fully serializes classes and traits (not its “definitions”)
  • Does not use the ClassBuilder during materialization. Tanker itself materializes the “class objects” and sets the data.

So far, we are missing:

  • The possibility to export source code (right now classes and methods do not have source code) and also to install it in the .changes file during import.
  • Some validations during import. For example, the superclass of a class being installed may have changed its shape and, therefore, the classes to install need recompilation (because the bytecodes accessing instVars offset may be shifted or wrong). Or if a class already exists in the image and the shape has changed, we need to update the existing instances.
  • Integration with other tools like Monticello and Metacello.

Results with the “current status”

There are so far 3 real examples of Tanker:

How to install it and use it

Tanker will work only in the bleeding edge of Pharo 2.0. So I first recommend you to get an image from Jenkins. Then, you can install Tanker this way:

Gofer it
 url: 'http://smalltalkhub.com/mc/marianopeck/Tanker/main';
 package: 'ConfigurationOfTanker';
(Smalltalk at: #ConfigurationOfTanker) load.

To export a package and provide yourself the classes and extension methods, you can:

| aPackage aStream |
aStream := 'demo.tank' asFileReference writeStream binary.
aPackage := TAPackage behaviors: {TestCase. TestLocalVariable. } extensionMethods: #().
TAPackageStore new storePackage: aPackage on: aStream.

aStream := 'demo.tank' asFileReference readStream binary.
TAPackageLoader new loadFrom: aStream.

Then you can also use the API that provides helper methods to RPackage and PackageInfo:

aPackage := TAPackage fromPackageInfoNamed: 'MyPackage'

You also have #fromPackagesInfoNames:, #fromRPackageNamed: and #fromRPackagesNames:. Of course, there are more use-cases, API and scenarios. But, so far, that is the simplest usage. For more examples, browse the class side methods of TankerExamples.

GSoC and “new status”

The results so far are quite promising and not anymore a “proof of concept”. However, we still need to support source code management as well as the already mentioned pending features. Because of this reason, Martin submitted Tanker for the GSoC and¬†fortunately¬†it was accepted. So, right now we are moving to a different design to solve the requirements. ¬†The idea now is NOT to serialize classes and traits, but instead serialize their “definition”. Imagine by “definition” the string used to create them. Then, during import, instead of just materializing class objects, we take the definition and, using the ClassBuilder or similar, we “evaluate” the definitions and we get the new classes.

At the same time, the idea is to export the source code of a package in a file (myPackage.tank.st or something like that) and the binary representation in another file (say myPackage.tank). Then, during import, you should be able to import with or without sources.

Side-effect projects of Tanker

You may be wondering why we didn’t start from the very beginning with the “definitions” way. Well, to be honest, the ClassBuilder is a mess, difficult to understand,¬†maintain¬†and extend. It was really hard trying to use it for our purpose. So the first “side-effect project” of Tanker is to continue pushing the “new ClassBuilder” started by Toon Verwaest¬†based in “slots”. Martin Dias, Guillermo Polito and Camillo Bruni are pushing it and writing tests. I think it could be soon integrated in Pharo and replace the old one. The idea is that Tanker will use this ClassBuilder, for example, to evaluate the definitions.

When we are importing a class, it may happen that the superclass (present in the image where we are importing) has changed its shape (added or removed instVars, change supperclass, etc). If this is true, we have to recompile because the bytecodes accessing intsVars will be a shifted offset. However, recompiling is slow and we don’t want that. Therefore, Tanker will use IR (intermediate representation) which was developed by Marcus Denker and the team working with the new Opal compiler. IR is just a nice model generated from a CompiledMethod. The idea is that we can generate the IR, modify it (bytecodes for instVars accessing, for example) using this nice abstraction and API and then generate back a new CompiledMethod. This is way faster than recompiling. Furthermore, IR is decoupled from Opal so we don’t need whole Opal.


Tanker started as an experiment to see whether Fuel coud be used to export and import packages in a binary way. The proof of¬†concept¬†was quite good so we are now going forward with the source code management and related stuff. It is important to notice that Tanker just “uses” Fuel. Fuel is¬†completely¬†decoupled from Tanker. We think Fuel was well received by the community.¬†We are doing our best so that Tanker gets positive feedback as well.