In a deployment perspective, I think that the usage of GAC (or shared assemblies) complicates the deployment process without adding much benefit.
Not only does it complicate the installation of new application, it also complicates the "upgrade" scenario for this applications.
I think I have read somewhere that it is better to keep the assemblies "private" (The main assembly and the dependency assemblies on the same directory) as much as possible. If multiple applications uses an assembly, they will have their own copy of it.
What is the benefit of using the GAC (other than the negligible performance upgrade)? Will it outweight the "configuration management" problems that it will present in the future? Or is it much better to keep the assemblies "private", if possible?
(Also, is there a scenario wherein one is forced to use the GAC?)
Thanks!
PS: I don't know if the term "private" assemblies properly describes the configuration I am talking about. I've opened a separate question for this.
Related
I have an application that contains close to 90 different projects written in at least 3 different languages (C#, Visual C++, and Visual Basic) targetting .NET 3, 3.5, 4.0, and 4.5,, with 6 different configurations. We are about to start scripting our compilations due to some messy configuration hassles involving preprocessing out features for different clients. I have seen multiple methods of using Powershell scripts to compile such applications but they seem to boil down to two options: compile the entire solution or compile each project individually.
So my question is: is there an industry best practice for such things? And if so what is it?
The project lead seems to be leaning toward compiling and individually configuring each project, but it seems wasteful since we already have configurations in VS to configure out individual projects. If this question is too subjective, I'd be happy to take it down. And sorry if my information is kind of vague, but I have to walk on egg shells with this project. Thanks.
If you are dealing with a large number of projects, and you are working with the Microsoft technology stack, the "Official" way to go would be to use Microsoft's full Team Foundation Server technology and formalize the development lifecycle.
It does Source Control, Build management, Testing, etc. I would then combine it with Release Management to more fully automate things.
The move to TFS is a big leap, and will require some time to get set up and configured, etc., but I think it is the best thing out there once you start reaching dozens of projects. PowerShell, and other methods are good, but become unmanageable when you are starting to scale out to large numbers of projects.
Over the years my application has grown from 1MB to 25MB and I expect it to grow further to 40, 50 MB. I don't use DLL's, but put everything in this one big executable.
Having one big executable has certain advantages:
Installing my application at the customer is really: copy and run.
Upgrades can be easily zipped and sent to the customer
There is no risk of having conflicting DLL's (where the customer has not version X of the EXE, but version Y of the DLL)
The big disadvantage of the big EXE is that linking times seem to grow exponentially.
Additional problem is that a part of the code (let's say about 40%) is shared with another application. Again, the advantages are that:
There is no risk on having a mix of incorrect DLL versions
Every developer can make changes on the common code which speeds up developments.
But again, this has a serious impact on compilation times (everyone compiles the common code again on his PC) and on linking times.
The question Grouping DLL's for use in Executable mentions the possibility of mixing DLL's in one executable, but it looks like this still requires you to link all functions manually in your application (using LoadLibrary, GetProcAddress, ...).
What is your opinion on executable sizes, the use of DLL's and the best 'balance' between easy deployment and easy/fast development?
A single executable has a huge positive impact on maintainability. It is easier to debug, deploy (size issues aside) and diagnose in the field. As you point out, it completely sidesteps DLL hell.
The most straightforward solution to your problem is to have two compilation modes, one that builds a single exe for production and one that builds lots of little DLLs for development.
The tenet is: reduce the number of your .NET assemblies to the strict minimum. Having a single assembly is the ideal number. This is for example the case for Reflector or NHibernate that both come as a very few assemblies. My company published free two white books on the topic One big executable or many small DLL's:
Partitioning code base through .NET assemblies and Visual Studio projects (8 pages)
Defining .NET Components with Namespaces (7 pages)
Arguments are developed in these white-books come with invalid/valid reasons to create an assembly and a case study on the code base of the tool NDepend.
The problem is that MS fosters(and is still fostering) the idea that assemblies are components while assemblies are just physical artifact to pack code. The notion of component is a logical artifact and typically an assemblies should contains several components. It is a good idea to partition component with the notion of namespaces although it is not always practicable (especially in the case of a framework with a public API where namespace are used to partition the API and not necessarily the components)
One big executable is definitely beneficial - you can have whole program optimization and less overhead and maintenance is much simpler.
As for the link time - you could have both the "many DLLs" and "one big executable" at the same time. For each DLL have a project configuration that builds a static library. So when you debug things you compile the "DLL" configuration of the project and when you need to ship you compile the "static library" configurations of your projects. Sometimes you will have different behavior in different configurations, but this will have to be addressed per incident.
An easier way to maintain large programs is to compose them into smaller manageable parts. A program can be composed into a shell and modules that add feature to the shell. Large programs like Visual Studio, outlook all use the same concepts. Try this approach to make a more maintainable and robust programs.
I am interested to know how people organise their code libraries, particularly with respect to reusable components. I am talking in OO terms below but I am interested in how your organise libraries for other types of language also.
For example:
Are you a stickler for class library projects for everything or do you prefer to keep everything in a single project?
Do you reuse your prebuilt DLLs or do you include individual classes from previous projects in your current work? If individual classes, do you share them between the projects to ensure all are kept up to date or do you permit branching?
How large are your reusable elements? How focussed are they? How are they focussed?
What level of reuse do you attain through your preferred practices?
etc.
EDIT
I am not looking for specific guidance here, I am just interested in people's thoughts and practices. I am particularly interested in the reuse of code between disparate projects, rather than within a single project. (Unfortunately the use of 'project' here is misleading - I mean reuse between real-world projects undertaken for customers, not projects in a Visual Studio sense.)
It generally can be guide by deployment considerations:
How will you deploy (i.e. what will you copy on your production machine) ?
If what you are deploying are packaged components (i.e. dll, jar, war, ...), it is wise to organize the "code library" as a collection of packaged set of files.
That way, you will develop directly with the -- dll, jar, war, ... -- which will be deployed on the production platform.
The idea being: if it works with those packaged files, it may still work in production.
the reuse of code between disparate projects, rather than within a single project.
I maintain that kind of reuse is easier in a "component" approach (like the one discussed in the question "Vendor Branches in GIT")
Over more than 40 current projects, we achieved:
technical reuse by systematically isolating any pure technical aspect into independent framework (typically, log framework, exception framework, KPI - Key Performance Indicator - framework, and so on).
Those technical components are reused into every other projects.
functional reuse by setting a clear applicative architecture in order to divide any functional domain (given the business and functional specifications) into well-defined applications. That would typically involve, for instance, a bus layer which is also a great candidate for exposing services reused by any other projects.
Summary:
For large functional domain, a single project being not manageable, a good applicative architecture will lead to natural code reuse.
We follow these principles:
The Release-Reuse Equivalency Principle: The granule of reuse is the granule of release.
The Common Closure Principle: The classes in a package should be closed together against the same kinds of changes.
The Common Reuse Principle: The classes in a package are reused together.
The Acyclic Dependencies Principle: Allow no cycles in the package dependency graph.
The Stable Dependency Principle: Depend in the direction of stability.
The Stable Abstraction Principle: A package should be as abstract as it is stable.
You can find out more over here and over here.
It depends on what platform you work. I'm a (proud) Java developer and we have nice tools to organise our dependencies such as Maven or Ivy
Whatever else you decide good source code control is crucial to this,as it allows you to implement your strategy whatever way you like without ending up with lots of unrelated copies of your libraries.good branching support is essential.
At work we're developing a large-scale application with quite a few front-end, back-end and support components. Typically the front-end is developed in C# and the back-end is developed in Java, although parts of the back-end are also developed in C# and possibly later C++.
The choice of language and platform is not arbitrary; we try to weigh the relative merits of each in development time, tool-chain cost, familiarity with the language by the specific development team etc. What all these components have in common, though, is that they are all required for the complete operation of the product, and that they are being developed concurrently by independent (but highly communicative) teams.
Previously, we have used Team Foundation Server for our .NET code and Subversion for our Java code; because there was clear separation of the teams' responsibilities, this caused little problem beyond the inconvenience of placing binaries (WARs, in this case) generated from one source tree in another, and the high manual overhead of keeping the branches and revisions in sync. With this project, the degree of separation between the teams is intentionally much smaller, and the volume of branching/merging is expected to be considerably higher; as a result we're moving to a unified VCS, more specifically Subversion.
This brings me to the meat of the question: how does one mix Java and C# code effectively? In practice, we'll have .NET code dependent on a Java codebase; the Java binaries are required to run anything other than unit test code (integration tests already require the binaries, and QA, acceptance testing etc. certainly does as well). What we currently have in mind looks something like:
/trunk
/java
/component1
/component2
/library1
/library2
/net
/assembly1
/assembly2
/...
project.sln
The idea is that the entire source tree is placed under one branch; the .NET code is dependant on the Java code, so we'll add a post-build step to the solution which will (most likely) call the ant script for the Java components. This allows branching of the entire codebase (for .NET developers) or just the Java components (for Java developers).
The problems with this solution are:
What happens when one of the two codebases becomes so large that making copies of it for every branch gets impractical? (our thoughts: split to separate repositories for .NET and Java code and use svn:externals, any input on this would be greatly appreciated).
We use Eclipse for Java development. How do we manage the "shared" workspace (i.e. which projects are required for which components, the dependency graph etc.)? Up until now we've had relatively few Java components, so each developer could just keep all of them in the workspace at the same time. With the increase in Java components and Java developers I don't see how we can keep doing that; any suggestions on how to keep the workspace versioned (a la solution files) while still maintaining sync between the two code-bases?
I would love to hear your input!
1: I've found it best to group things by component, rather than langugage. If one component requires several languages for interface, you still need to develop, test and release them as one. So, splitting a component across several repos is not a good idea.
If one part of the code depends tightly on the other, keep it together. Better to split components across repos. (This even goes for internal structure, where, especially as things grow, it's difficult if you package things by type, rather than by function, i.e. in MVC, don't have three huge packages for each category, rather keep FooView, FooModel and FooController tight.)
svn:externals might work, and with the later versions I think you can use "internals", i.e. link to other dirs in the same repo. That is miles easier than managing separate repos, especially with tagging and branching. (shudder)
2: You could always have the developers setup different workspaces, or perhaps use working sets. Commercial Eclipse releases has better support for sharing workspace settings than the OS variant. (Haven't tried, only worked and been frustrated with the OS one)
I've done C++ (MSVS) and Java (Eclipse) in one repo, and it works pretty well. Also C++/Python similarly. Make sure your build system supports building and testing everything (even if your IDEs only build one part).
I'm fairly new to reflection and I was wonder what I would use a (second) AppDomain for? What practical application would one have in a business application?
There are numerous uses. An secondary AppDomain can provide a degree of isolation that is similar to the isolation an OS provides processes.
One practical use that I've used it for is dynamically loading "plug-in" DLLs. I wanted to support scanning a directory for DLLs at startup of the main executable, loading them and checking their types to see if any implemented a specific interface (i.e. the contract of the plug-in). Without creating a secondary AppDomain, you have no way to unload a DLL/assembly that may not have any types that implement the interface sought. Rather than carry around extra assemblies and types, etc. in your process, you can create a secondary AppDomain, load the assembly there and then examine the types. When you're done, you can get rid of the secondary AppDomain and thus your types.
99% of the time I would avoid additional AppDomains. They are essentially separate processes. You must marshal data from one domain to the other which adds complexity and performance issues.
People have attempted to use AppDomains to get around the problem that you can't unload assemblies once they have been loaded into an AppDomain. So you create a second AppDomain where you can load your dynamic Assemblies and then unload the complete AppDomain to free the memory associated with the Assemblies.
Unless you need to dynamically load & unload Assemblies they are not really worth worrying about.
AppDomains are useful when you have to have multiple instances of a singleton. For example, you have an assembly that implements a communication protocol to some device and this assembly uses singletons. If you want to instantiate multiple instances of this class (to talk to multiple devices) and you want the instances to not interfere with one another, then AppDomains are perfect for this purpose.
It does make programming more difficult, however, as you have to do more work to communicate across AppDomain boundaries.