NetBeans Architecture Answers for Master Filesystem module

General Information

Question (arch-what): What is this project good for?
Answer: MasterFileSystems is just implementation of FileSystem provided in standalone module including implementation of URLMapper that resolves file protocol and is responsible for conversion from URL into FileObject and vice versa. Implementation just delegates to the other FileSystem implementations (LocalFileSystem, VCSFileSystem, ...) and playes the role of arbiter that controls instantiation and life cycle of provided FileObjects. MasterFileSystemAPI
Question (arch-overall): Describe the overall architecture.
Answer: MasterFileSystem exports SPI for versioning support. There is expected that module that provides implementation of FileSystem that should be plugable into MasterFileSystem must implement at least FileSystemProvider. MasterFileSystem doesn't provide pure client API but has tiny API that is intended just for SPI providers (slightly disputable if it should be called API or SPI). All SPI are plugable, registred by Lookup.
Question (arch-usecases): Describe the main use cases of the new API. Who will use it under what circumstances? What kind of code would typically need to be written to use the module?
Answer: MasterFileSystem is just implementation of FileSystem. There are no special use cases. FileObjects erlier returned from URLMapper or FileUtil.fromFile provided by LocalFileSystem or CvsFileSystem will be now provided by MasterFileSystem. There will be guaranteed that there won't be more instances of FileObject addressing one java.ioFile.
Question (arch-time): What are the time estimates of the work?
Answer: MasterFileSysetm is already implemented, tested and used in current dev builds. There are a few requests for enhancements including API changes that should be incorporated. Expected milestone is promo-D. Currently there doesn't exist any SPI provider that supports automounting (AutoMountProvider), this feature isn't tested yet and isn't planned to be used in promo-D.
Question (arch-quality): How will the quality of your code be tested and how are future regressions going to be prevented?
Answer: Junit tests as much as possible and as soon as possible.
Question (arch-where): Where one can find sources for your module?
WARNING: Question with id="arch-where" has not been answered!

Project and platform dependencies

Question (dep-nb): What other NetBeans projects and modules does this one depend on?
Answer:
• UtilitiesAPI
• LookupAPI
• FilesystemsAPI

The default answer to this question is:


These modules are required in project.xml:

• GeneralQueriesAPI - The module is needed for compilation. The module is used during runtime. Specification version 1.27 is required.
• FilesystemsAPI - The module is needed for compilation. The module is used during runtime. Specification version 7.61 is required.
• ModulesAPI - The module is needed for compilation. The module is used during runtime. Specification version 7.29 is required.
• UtilitiesAPI - The module is needed for compilation. The module is used during runtime. Specification version 8.3 is required.
• LookupAPI - The module is needed for compilation. The module is used during runtime. Specification version 8.0 is required.
Question (dep-non-nb): What other projects outside NetBeans does this one depend on?
Answer: None.
Question (dep-platform): On which platforms does your module run? Does it run in the same way on each?
Answer: Any. There is special implementation of root on Windows which has children corresponding to logical drives (A:, C:, D: ...) , has no delegate, there doesn't exist conversion to java.io.File, calling refresh checks logical drives and fires regular events.
Question (dep-jre): Which version of JRE do you need (1.2, 1.3, 1.4, etc.)?
Answer: 1.4
Question (dep-jrejdk): Do you require the JDK or is the JRE enough?
Answer: JRE is enough.

Deployment

Question (deploy-jar): Do you deploy just module JAR file(s) or other files as well?
Answer: Just one module JAR file.
Question (deploy-nbm): Can you deploy an NBM via the Update Center?
Answer: Yes.
Question (deploy-shared): Do you need to be installed in the shared location only, or in the user directory only, or can your module be installed anywhere?
Answer: Module can be installed anywhere.
Question (deploy-packages): Are packages of your module made inaccessible by not declaring them public?
Answer:

The entire API and SPI are in its own public packages.

The implementation is in another package and is not considered public.

Question (deploy-dependencies): What do other modules need to do to declare a dependency on this one, in addition to or instead of the normal module dependency declaration (e.g. tokens to require)?
Answer: Nothing currently. Most "clients" are really callers of FileUtil.toFileObject and so on, and thus implicitly depend on the existence of this module. In the future a provide-require token might make sense.

Compatibility with environment

Question (compat-i18n): Is your module correctly internationalized?
Answer: Implemented with I18N instructions in mind.
Question (compat-standards): Does the module implement or define any standards? Is the implementation exact or does it deviate somehow?
Answer: It implements the FileSystem API. No intentional deviations.
Question (compat-version): Can your module coexist with earlier and future versions of itself? Can you correctly read all old settings? Will future versions be able to read your current settings? Can you read or politely ignore settings stored by a future version?
Answer: No settings at all.
Question (compat-deprecation): How the introduction of your project influences functionality provided by previous version of the product?
WARNING: Question with id="compat-deprecation" has not been answered!

Access to resources

Question (resources-file): Does your module use java.io.File directly?
Answer: Yes, this module provides implementation of FileSystem addresing resources accessible by java.io.File.
Question (resources-layer): Does your module provide own layer? Does it create any files or folders in it? What it is trying to communicate by that and with which components?
Answer: Yes, MasterFileSystem is automaticaly mounted into Repository via its registration in /Mount folder in mf-layer.
Question (resources-read): Does your module read any resources from layers? For what purpose?
Answer: No hidden intermodule dependency.
Question (resources-mask): Does your module mask/hide/override any resources provided by other modules in their layers?
Answer: No.
Question (resources-preferences): Does your module uses preferences via Preferences API? Does your module use NbPreferences or or regular JDK Preferences ? Does it read, write or both ? Does it share preferences with other modules ? If so, then why ?
WARNING: Question with id="resources-preferences" has not been answered!

Lookup of components

Question (lookup-lookup): Does your module use org.openide.util.Lookup or any similar technology to find any components to communicate with? Which ones?
Answer: All registered FileSystemProvider and AutoMountProvider instances are queried and used.
Question (lookup-register): Do you register anything into lookup for other code to find?
Answer: URLMapper implementation is registered using META-INF/services. URLMapper is supposed to find it (may sound strange but in filesystems isn't separated API, SPI and implementation).
Question (lookup-remove): Do you remove entries of other modules from lookup?
Answer: No.

Execution Environment

Question (exec-property): Is execution of your code influenced by any environment or Java system (System.getProperty) property? On a similar note, is there something interesting that you pass to java.util.logging.Logger? Or do you observe what others log?
Answer: No properties.
Question (exec-component): Is execution of your code influenced by any (string) property of any of your components?
Answer: refreshSlow - One can ask FileObject.getAttribute("refreshSlow") and obtain an instance of Runnable with intricate behavior. This is a private contract used from core.ui module to show refresh progress and tested in masterfs/test/unit/src/org/netbeans/modules/masterfs/SlowRefreshTest.java. org.netbeans.modules.masterfs.watcher.disable - It is possible to disable native listening on filesystem changes. Useful mostly in testing environment, but it may be interesting for some users too. Don't rely (much) on this property from production code however. org.netbeans.modules.masterfs.watcher.FAM - It is possible to enable use of FAM notifier on Solaris disabled by default. Useful mostly in testing environment, but it may be interesting for some users too. Don't rely (much) on this property from production code however.
Question (exec-ant-tasks): Do you define or register any ant tasks that other can use?
WARNING: Question with id="exec-ant-tasks" has not been answered!
Question (exec-classloader): Does your code create its own class loader(s)?
Answer: No.
Question (exec-reflection): Does your code use Java Reflection to execute other code?
Answer: No.
Question (exec-privateaccess): Are you aware of any other parts of the system calling some of your methods by reflection?
Answer: I'm not aware.
Question (exec-process): Do you execute an external process from your module? How do you ensure that the result is the same on different platforms? Do you parse output? Do you depend on result code?
Answer: No.
Question (exec-introspection): Does your module use any kind of runtime type information (instanceof, work with java.lang.Class, etc.)?
Answer: Naturally this module uses instanceof but I don't think its usage isn't suspicious or worth of mentioning.
Question (exec-threading): What threading models, if any, does your module adhere to? How the project behaves with respect to threading?
Answer: Supposed to be thread-safe - complex fine-grained locking. Relies on Filesystems thread semantics.
Question (security-policy): Does your functionality require modifications to the standard policy file?
WARNING: Question with id="security-policy" has not been answered!
Question (security-grant): Does your code grant additional rights to some other code?
WARNING: Question with id="security-grant" has not been answered!

Format of files and protocols

Question (format-types): Which protocols and file formats (if any) does your module read or write on disk, or transmit or receive over the network? Do you generate an ant build script? Can it be edited and modified?
Answer: No.
Question (format-dnd): Which protocols (if any) does your code understand during Drag & Drop?
Answer: No.
Question (format-clipboard): Which data flavors (if any) does your code read from or insert to the clipboard (by access to clipboard on means calling methods on java.awt.datatransfer.Transferable?
Answer: No.

Performance and Scalability

Question (perf-startup): Does your module run any code on startup?
Answer: MasterFileSystem is just instantiated by AutomountSupportcode>.
Question (perf-exit): Does your module run any code on exit?
Answer: No.
Question (perf-scale): Which external criteria influence the performance of your program (size of file in editor, number of files in menu, in source directory, etc.) and how well your code scales?
Answer: The higher number of registered instances of AutoMountProvider and the higher number of mounted filesystems then more negatively affected performance.
Question (perf-limit): Are there any hard-coded or practical limits in the number or size of elements your code can handle?
Answer: No hard-coded limits. Practical limit of registered instances of AutoMountProvider depends on performance meassurement.
Question (perf-mem): How much memory does your component consume? Estimate with a relation to the number of windows, etc.
Answer: Memory occupation varies widely - the more FileObjects are requested the higher memory consumption.
Question (perf-wakeup): Does any piece of your code wake up periodically and do something even when the system is otherwise idle (no user interaction)?
Answer: No polling.
Question (perf-progress): Does your module execute any long-running tasks?
Answer: Mounting new FileSystem could be considered long-running task under some circumstances. Cache with living FileObjects must be traversed and delegates are changed if necessary.
Question (perf-huge_dialogs): Does your module contain any dialogs or wizards with a large number of GUI controls such as combo boxes, lists, trees, or text areas?
Answer: No.
Question (perf-menus): Does your module use dynamically updated context menus, or context-sensitive actions with complicated and slow enablement logic?
Answer: No.
Question (perf-spi): How the performance of the plugged in code will be enforced?
Answer: No enforcement.