MEF Plugin update strategies for winforms - plugins

I'm developing an extensible application with MEF. The application will have many types of plugins to collect and process data in different ways.
I'm thinking about building a versioned online repository for the plugins, that will enable the user to download new versions of the plugins when they become available.
It would be nice if MEF could load different versions of the same plugin simultaneously, though from what I understand this isn't possible (correct me if I'm wrong).
So I've resigned myself to the fact I will need to update the plugin and archive the previous version.
What would be the best strategy for doing this?
Example 1
The Application downloads a new version of a loaded running plugin. I can't place the plugin in the plugin directory as there is already DLL with the same name. So I could rename the new plugin with a version suffix. I can't load the same assembly, so I guess I'll have to force a restart. So on restart, it achieves the old plugin and loads the new one.
--- This seems solutions seems a little messy
Example 2
The Application downloads a new version of a loaded running plugin.
The plugin is encased in some type of installer.
The installer closes the host gracefully and archives the existing plugin.
The installer installs new plugin and restarts the host app.
--- this also seems a little messy
I am seeking any correction of my assumptions, or any insight into a successful strategy to my achieve my goal.

The .NET Framework has a fearure called Shadow Copy which allows you to update loaded assebmlies. Basically it copies the assemblies to a temp folder and loads them from there. This way the assemblies located in your application's installation folder will not be locked by the OS and you will be able to replace them. ASP.NET, unit test framweorks and many other applications use shadow copying.
To enable this feature you will need to load your application in a new AppDomain since you cannot enable shadow copying on the main AppDomain. You can create a simple loader that will create an AppDomain and execute your application there. This is very straight forward. For an example of MEF + Shadow Copy have a look at Glenn Block's Way of MEF and in particullar the PartUpdatesInPlace sample.
Now as far as versioning is concerned you will need to be able to have two or more versions of an assembly loaded at the same time in the same application domain. There are two ways to do this:
Strong named assemblies in the GAC.
Assemblies with the version included in their name (like Plugin.v1.dll). Strong naming is optional in this case but a good idea nonetheless. The advantage of this approach is that two or more versions of a plugin can coexist in the same directory.
Have a look at this answer for an example of MEF + Versioning.
You can even use the recomposition feature of MEF and have your plugin container updated after:
A new plugin assembly is added
A plugin assembly is deleted
A plugin assembly is replaced
Have a look at this question for an example.

Related

How to reference a specific DLL for functionality in said DLL

Good day,
I have an application that I developed that transfers files between two machines ("site" and "server"). This application was set to target dotNet 3.5. Furthermore, I am using Renci.SshNet to handle the connections between the machines and the transferring of said files.
The issue that I am facing currently though is that about 70% of the "site" machines do not have a standard dotNet and is also quite old; thus these machines do not support all the required functionality as the external dll makes calls to System.Threading.WaitHandle.WaitOne() and System.Threading.WaitHandle.WaitAny(WaitHandle[], Int32) and other overloads of these methods.
The workaround that I have for this though is to install netfx20SP2 or netfx30SP1, yet I am not in the position to perform this update on all machines as they are scattered across the country and have data limitations (bandwidth and cap).
What I want to do possibly is to embed the System.Threading dll that I have downloaded and then the application should use those classes instead, or alternatively just point the application to use the said dll.
Is this at all possible, or do you have to load the dll into the GAC? And also, will it be possible to "run" this higher version of System.Threading in the application while the system itself is on a lower framework version. Something is telling me that the best bet will be to actually run the service pack installation to avoid unnecessary coding but I'm not sure exactly how to approach this.
Thank you in advance for any assistance / suggestions,
JD
To allow the execution of an application that, let's say, targets .Net 4; while the machine itself only has let's say, .Net 3.5, installed, one can redirect Windows to check the local (executing) directory for dlls that should contain the required symbols loaded into memory instead of the default symbols that get loaded upon execution (the default would be the NetFx installed on the machine - which I believe the highest version of the framework that can be found upon loading when the execution starts or would be the highest available version that is lower or equal to the targeted framework).
This file's contents (myApp.exe.local) are ignored. It is just there to tell Windows to
look in that folder for the applicable symbols and if not found, the system will roll back to attempt to load these symbols from the NetFx directory.
Read more at Microsoft Dev Center - Docs (link is attached to the following paragraph which is a Copy-Paste of a section of this document).
To use DLL redirection, create a redirection file for your application. The redirection file must be named as follows: App_name.local. For example, if the application name is Editor.exe, the redirection file should be named Editor.exe.local. You must install the .local file in the application directory. You must also install the DLLs in the application directory.

how to put to work Ionic generator?

I have an Ionic app running with the basics of Ionic and running it in the browser by doing ionic serve, but I want some new stuff and run it trough the grunt serve command, also has the feature for JSLint, I am already using this scss this: https://github.com/diegonetto/generator-ionic/ and I see that have everything I want, how do I install that in my project?
Take into account that my project is almost done, I have almost 85 % already done.
Is this the part I need to follow up:
Upgrading
Make sure you've committed (or backed up) your local changes and install the latest version of the generator via npm install -g generator-ionic, then go ahead and re-run yo ionic inside your project's directory.
The handsome devil is smart enough to figure out what files he is attempting to overwrite and prompts you to choose how you would like to proceed. Select Y for overwriting your Gruntfile.js and bower.json to stay up-to-date with the latest workflow goodies and front-end packages.
does this will bring some complications ? is there something else I need to know ?
I use the same generator and enjoy using it. With that said, I would not recommend starting to use a generator until you've made a complete backup of your project.
Even then, I'd recommend creating a brand new project using the generator then migrating your existing code into the newly generated project. While migrating, you should be modifying your code to match the generator conventions as you go. This gives you the most control and will make sure that you learn the conventions of the new project structure. Upgrading instructions are really meant for people who already use the generator and are just upgrading to a new version of the generator. They are not applicable to you.

Is using GACUtil in your coding/svn/development workflow considered Bad Practice?

There's plenty of information/blogs/msdn articles around on NOT using GACUtil in your Deployment/Release scenarios and that MSI or another windows installer technology is a far better option.
However is it still appropriate to use GACUtil in your Development work flow.
We have a number of DLLs that are strong named & referenced from the GAC. In order to keep the development team in sync, once a new version of the GAC-able DLL is generated it's automatically added to all other developers GAC's as part of their daily trunk checkout. Workflow goes something like:
A Developers makes a change to one of our GAC-able assemblies, tests it locally, and once signed off, compiles a release version of the DLL
Release version is copied from \Project_DIR\bin\Release*.dll -> \COMPANY_GAC\Current*.dll
Other devs run our Source Control check out batch scripts which:
Check out newest versions of COMPANY_GAC\Current*.dll
Run GacUtil.exe on each DLL
This has worked for us up until now, but it's getting a little more complex with:
- Larger Team, more stringent management of GAC Changes.
- CLR2.0 & CLR4.0 compiled Company_Gac assemblies requiring different versions of GACUtil.exe
- Managing assemblies on Build/Integration Servers which have multiple feature branches (and hence having to hot-swap different GAC Dlls)
Should we be looking at something more robust that GACUtil & Scripts to manage this?
One consideration was to roll something ourselves in powershell to check the Assembly type and add the assemblies to the correct GAC. Has anyone done this?
Any other suggestions on how developers manage their GAC workflow would be welcome.
Not using gacutil.exe during deployment is an easy one: it isn't available on the target machine since it is a Windows SDK utility and it is not a re-distributable component.
Using it during development certainly isn't popular. Most typically you'd use a solution with the dependent projects included so that you'll automatically get the latest build with local deployment and no need for the GAC. That goes well up to a point, build times can require starting distributing swords when the solution gets too massive.
No magic solutions past that point, the GAC certainly helps to get build times down again. In general, churn in the foundation assemblies should start with minus 1000 points, they can cause a lot of pain. Save them up for only, say, weekly release updates. Off hand, there's also the core need to get all this stuff properly installed on the client machines. If nobody has focused on that yet, maybe now is a good time to get that solid. Which automatically gets debugged when everybody uses it to get the assemblies they need on their machine.

Storing third-party framework/middleware into source control that needs to alter your compiler/IDE

I know there are posts that ask how one stores third-party libraries into source control (such as this and this). While those are great answers, I still can't find the answer to this:
How do you store third-party middleware/frameworks binaries that need to alter your compiler / IDE for the library to work properly? Note: for my needs, I don't need to store the middleware source, I only store header files / lib / JAR ..so that it's ready to be linked.
Typically, you simply link libraries to your app, and you are good. But what about middleware / frameworks that need more?
Specific examples:
Qt moc pre-processor.
ZeroC Ice Slice (ice) compiler (similar to CORBA IDL preprocessor).
Basically these frameworks/middleware need to generate their own code before your application can link to it.
From the point of view of the developer, ideally he wants to just checkout, and everything should be ready to go. But then my IDE/compiler will not be setup properly yet, so the compilation will fail..
What do you think?
Backup everything including the setup of the IDE, operating system, etc. This is what i do
1) Store all 3rd party libraries in source control. I have a branch for all the libraries.
2) Backup the entire tool chain which was used to build. This includes every tool. Each tool is installed into the same directory on each developers computer, so this makes it simple to setup a developers machine remotely.
3) This is the most hardcore, but prepare 1 perfect developer IDE setup which is clean, then make a VMWare / VirtualPC image out of it. This will be useful when you cant seem to get the installers to work in future.
I learned this lesson the painful way because I often have to wade through visual studio 6 code which don't build properly.
I think that a better solution is to make sure that the build is self-contained and downloads all necessary software for itself unless you tell it otherwise. This is the way maven works, and it is really handy. The downside is that it sometimes needs to download a application server or similar, which is highly unpractical, but at least the build succeeds and it becomes the new developers responsibility to improve the build if needed.
This does of course not work great if your software needs attended installs, but I would try to avoid any such dependencies in any case. You can add alternative routes (e.g the ant script compiles the code if eclipse hasn't done it yet). If this is not feasible, an alternative option is to fail with a clear indication of what went wrong (e.g 'CORBA_COMPILER_HOME' not set, please set and try again').
All that said, the most complete solution is of course to ship everything with your app (i.e OS, IDE, the works), but I doubt that that is applicable in the general case, how would you feel about that type of requirements to build a software product? It also limits people who want to adapt your software to new platforms.
What about adding 1 step.
A nant script which is started with a bat file. The developer would only have to execute one .bat file, the bat file could start nant, and the Nant script could be made to do anything you need.
This is actually a pretty subtle question. You're talking about how to manage features of the environment which are necessary in order to allow your build to proceed. In this case it's the top level of your code toolchain, but the problem can be generalised to include the entire toolchain, and even key aspects of the operating system.
In my place of work, we have various requirements of the underlying operating system before our code will successfully run. This includes machine-specific configurations as well as ensuring correct versions of system libraries and language runtimes are present. We've dealt with this by maintaining a standard generic build machine image which contains the toolchain requirements we need. We can push this out to a virgin machine and get a basic environment that contains the complete toolchain and any auxiliary programs.
We then use fsvs to version control any additional configuration, which can be layered on to specific groups of machines as needed.
Finally, we use custom scripts hooked in to our CI server (we use Hudson) to perform any pre-processing steps required for specific projects.
The main advantages for us of this approach is:
We can build and deploy developer and production machines very easily (and have IT handle this side of the problem).
We can easily replace failed machines.
We have a known environment for testing (we install everything to a simulated 'production server' before going live).
We (the software team) version control critical configuration details and any explicit pre-processing steps.
I would outsource the task of building the midleware to a specialized build server and only include the binary output as regular 3rd party dependencies under source control.
If this strategy can be successfully applied depends on whether all developers need to be able to change midleware code and recompile it frequently. But this issue could also be solved via a Continous Integration Server like Teamcity that allows to create private builds.
Your build process would look like the following:
Middleware repo containing middleware code
Build server, building middleware
Push middleware build output to project repository as 3rd party references
Update: This doesn't really answer how to modify the IDE. It's just a sort-of Maven replacement thingy for C++/Python/Java. You shouldn't need to modify the IDE to build stuff, if so, you need a different IDE or a system that generates/modifies IDE files for you. (See CMake for a cross-platform c/c++ project file generator.)
I've written a system (first in Ant/Beanshell at two different places, then rewrote it in Python at my current job) where third-partys are compiled separately (by someone), stored and shared via HTTP.
Somewhat hurried description follows:
Upon start, the build system looks through all modules in repo, executes each module's setup target, which downloads the specific version of a third-party lib or app that the current code revision uses. These are then unzipped, PATH/INCLUDE etc are added to (or, for small libs, copy them to a single directory for the current repo) and then launches Visual Studio with /useenv.
Each module's file check for stuff that it needs, and if it needs installing and licensing, such as Visual Studio, Matlab or Maya, that must be on the local computer. If that's not there, the cmd-file will fail with a nice error message. This way, you can also check that the correct version is in there
So there are a number of directories on the local disk involved. %work% needs to be set using an global environment variable, preferrable on a different disk than system or source-checkout, at least if doing heavy C++.
%work% <- local store for all temp files, unzip, and for each working copy's temp files
%work%/_cache <- downloaded zips (2 gb)
%work%/_local <- local zips (for development or retrieved in other manners while travvelling)
%work%/_unzip <- unzips of files in _cache (10 gb)
%work%&_content <- textures/3d models and other big files (syncronized manually, this is 5 gb today, not suitable for VC either)
%work%/D_trunk/ <- store for working copy checked out to d:/trunk
%work%/E_branches/v2 <- store for working copy checked out to e:/branches/v2
So, if trunk uses Boost 1.37 and branches/v2 uses 1.39, both boost-1.39 and boost-1.37 reside in /_cache/ (as zips) and /_unzip/ (as raw files).
When starting visual studio using bat files from d:/trunk/BuildSystem/Visual Studio.cmd, INCLUDE points to /_unzip/boost-1.37, while if runnig e:/branches/v2/BuildSystem/Visual Studio.cmd, INCLUDE points to /_unzip/boost-1.39.
In the repo, only a small set of bootstrap binaries need to be stored (i.e. wget and 7z).
We currently download about 2 gb of packed data, which is unzipped to 10 gb (pdb files are huge!), so keeping this out of source control is essential. Having this system allows us to keep the repo size small enough to use DVCS such as Mercurial (or Git) instead of SVN, which is very nice. (I'm thinking of using Mercurials bigfiles extension or file sharing instead of a separately http-served directory.)
It work flawlessly. Developers need only to check out, set an enviroment variable for their local cache, then run Visual Studio via a specific batch-file in the repo. No unzipping or compiling or stuff. A new developer can set up his computer in no time. (Installing Visual Studio takes the order of a magnitude more time.)
First time on a new computer takes some time, but then it's fast, only a few seconds. Downloads/unzips are shared on the local computer, do checking out additional branches/versions does not occupy more space. Working offline is also possible, you just need to get the zip files manually if new ones have been uploaded. (This mechanism is essential to test new versions/compilations of third-party libraries.)
The basics are in a repo on bitbucket but it needs more work before it's ready for the public. Apart from doc and polish, I plan to:
extend it to use cmake instead of raw
vcproj-files, to make it more
cross-platform.
script the entire
process from checkout/download of
third-party packages to building and
zipping them (including storing the
download in a local repo) ... currently that's on my dev computer. Not good. Will fix. :)
As for moc, we use Qt's Visual Studio add-in, which stores this in the .vcproj files. Works well. I do think that CMake is one of the best answers for this though

P2 headless update not working

I have taken the org.eclipse.equinox.p2.examples.rcp.prestartupdate project and adapted it for use in my RCP application. I then setup an update repository that gets updated as part of my nightly build.
When I open my application it goes through the motions like it is updating - it finds the update site, generates an uninstall and install operand for each bundle correctly and says that it finished with no errors. The problem is that the plugins never actually get installed in the plugins folder even though the profile gets updated (a subsequent run states there are no updates). Next time my build runs it correctly identifies there are updates, but the same thing happens again.
I have spent days debugging and the only thing that looks out of the ordinary (not that I fully understand what is going on) is that during the final configure phase none of the TouchpointData objects have any instructions so it doesn't look like configure is doing what it should.
I really have no clue where to look next and would like to see if anyone else has any ideas.
Update:
I finally figured out what was going on.
The problem started when I built my product without the generating the metadata repository. When building through Eclipse I didn't check the "Generate metadata repository" in the export product wizards because I didn't need a p2 repository, just the product. The problem is that without checking that button the product does not install as P2 enabled causing side effects such as not generating a profile among other things.
I tried to compensate for this by manually creating a profile in code which I have since found out is a really bad idea. My original problems were created because my profile wasn't set up correctly.
Once I started exporting the product with "Generate metadata repository" checked the update started correctly installing the new plugins.
The problem I have now is that although the plugins are being installed correctly, the executable is getting trashed and I cannot launch my application any more. I am building my update site through Hudson and the binary folder which is present when I use the Eclipse Export Product wizard is missing. I am assuming that is what is going wrong now.
Any ideas why the binaries would not be building in my headless PDE build?
Figured this out also. I had assumed that all I needed was the individual launcher plugins for the platforms I wanted to build on. Since I was trying to understand the process I was copying over plugins one by one to the build server. It turns out to include the platform specific binaries in the build you need to have the org.eclipse.equinox.executable feature from the delta pack. Once I added that to the build the binaries started showing up in the output. With the binaries the update mechanism works exactly as intended.
I had assumed that all I needed was the individual launcher plugins for the platforms I wanted to build on. Since I was trying to understand the process I was copying over plugins one by one to the build server. It turns out to include the platform specific binaries in the build you need to have the org.eclipse.equinox.executable feature from the delta pack. Once I added that to the build the binaries started showing up in the output. With the binaries the update mechanism works exactly as intended.