NetBeans Architecture Answers for External Execution Base API module

General Information

Question (arch-what): What is this project good for?
Answer:

Provides common APIs to execute external process and to handle its streams and process the output. Input/line processing can be used as separate part.

Question (arch-overall): Describe the overall architecture.
Answer:

This API origins in External Execution API and contains set of basic features with minimal dependencies. For the better integration with the IDE check also original External Execution API.

To see the simplest usage of this API to handle external process see documentation of BaseExecutionService

The External Execution Base module provides the ExternalExecutionBaseAPI that contains support for execution of external processes. There is also abstraction of process builder and support class for extended process handling.

Another exported API ExternalExecutionBaseInputAPI define interfaces for input processing (character or line based) and provides common implementations of these with factory methods.

The SPI ExternalExecutionBaseSPI allows different implementations of process builder and defined interface for extended process handling support.

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:

Execution of an external process

Client needs to execute an external process and handle process streams.

In order to achieve this client creates the BaseExecutionDescriptor. Via this object client configures all the client integration parameters of the execution. As a next step client creates the BaseExecutionService itself and calls run to execute the job. Run can be called multiple times. The output and input streams are handled by the service. Additional processing can be configured in descriptor through interfaces described in following usecases.

The creation of the external process is supported by ProcessBuilder to make things easier.

Processing the input

Client needs to process character data coming from stream, file or other source.

To abstract the source of the data client must implement InputReader. To abstract the data processing client must implement InputProcessor or LineProcessor. For all three interfaces there are prepared common implementations (and bridge from character based to line based processing) at these three factory classes:

• InputReaders
• InputProcessors
• LineProcessors

Once the data source and processing objects are prepared client creates InputReaderTask. Factory methods of the InputReaderTask can create either common task exiting on interruption or cancellation or draining task which is trying to drain out all available data before exiting.

Custom process builder

Third party wants to implement custom process builder to provide additional functionality, such as remote execution.

In order to do so it will implement ProcessBuilderImplementation and pass ProcessBuilder to its clients. The API instances are created with help of ProcessBuilderFactory.

Destroying a process

Client wants to destroy the process, trying to kill whole process tree. Method Processes.killTree(java.lang.Process process, Map<String,String> environment) is designed for that. It will use a ProcessesImplementation registered in default lookup to do so.

Question (arch-time): What are the time estimates of the work?
Answer:

Written and functional. Compatible changes can occur in future.

Question (arch-quality): How will the quality of your code be tested and how are future regressions going to be prevented?
Answer:

Most of the API functionality is covered by unit tests. Same applies to future enhancements.

Question (arch-where): Where one can find sources for your module?
Answer:

The sources for the module are in the Apache Git repositories or in the GitHub repositories.

Project and platform dependencies

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

These modules are required in project.xml:

• CommonAnnotationsAPI - The module is needed for compilation. The module is used during runtime. Specification version 1.0 is required.
• WeakListener.setAccessible - The module is needed for compilation. The module is used during runtime. Specification version 9.3 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:

No known platform dependencies.

Question (dep-jre): Which version of JRE do you need (1.2, 1.3, 1.4, etc.)?
Answer:

1.5

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 the single 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:

Anywhere.

Question (deploy-packages): Are packages of your module made inaccessible by not declaring them public?
Answer:

Only API packages are exported.

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.

Compatibility with environment

Question (compat-i18n): Is your module correctly internationalized?
Answer:

Yes.

Question (compat-standards): Does the module implement or define any standards? Is the implementation exact or does it deviate somehow?
Answer:

No.

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:

Yes. No settings stored.

Question (compat-deprecation): How the introduction of your project influences functionality provided by previous version of the product?
Answer:

The module languages.execution should be removed as it provides not well stabilized subset of the same functionality.

Access to resources

Question (resources-file): Does your module use java.io.File directly?
Answer:

Yes.

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:

No.

Question (resources-read): Does your module read any resources from layers? For what purpose?
Answer:

No.

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 ?
Answer:

No.

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:

The class for extended process handling Processes is trying to lookup an implementation ProcessesImplementation in default lookup.

Question (lookup-register): Do you register anything into lookup for other code to find?
Answer:

No.

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.

Question (exec-component): Is execution of your code influenced by any (string) property of any of your components?
Answer:

No.

Question (exec-ant-tasks): Do you define or register any ant tasks that other can use?
Answer:

No.

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:

No.

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:

Yes. The API provides support to do so. The result code, input and output stream content does not define API as this is forwarded to the client of this module.

Question (exec-introspection): Does your module use any kind of runtime type information (instanceof, work with java.lang.Class, etc.)?
Answer:

No.

Question (exec-threading): What threading models, if any, does your module adhere to? How the project behaves with respect to threading?
Answer:

Each class and factory method defines the thread safety of the class. If this is missing by accident method can be called from any thread.

Question (security-policy): Does your functionality require modifications to the standard policy file?
Answer:

No.

Question (security-grant): Does your code grant additional rights to some other code?
Answer:

No.

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:

None.

Question (format-dnd): Which protocols (if any) does your code understand during Drag & Drop?
Answer:

None.

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:

None.

Performance and Scalability

Question (perf-startup): Does your module run any code on startup?
Answer:

No.

Question (perf-exit): Does your module run any code on exit?
Answer:

On JVM shutdown module tries to terminate any running process executed through the API.

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:

Number of threads depending on number of spawned processes (n) increases lineary (4n the worst case, 2n the best case).

Question (perf-limit): Are there any hard-coded or practical limits in the number or size of elements your code can handle?
Answer:

Any spawned process needs 4 threads (the worst case). One as the process handler, one for the standard input, one for the standard output and one for the standard error output. The minimal number of threads to handle a process is 2 (process handler and standard output handler - standard error output is redirected to the output, no thread for the standard input).

Typically the client should not run more than 10 external processes concurrently.

Question (perf-mem): How much memory does your component consume? Estimate with a relation to the number of windows, etc.
Answer:

The small amount of the memory is consumed by caching data structures like available output tabs and currently executed processes.

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.

Question (perf-progress): Does your module execute any long-running tasks?
Answer:

Executing external processes. Always scheduled to dedicated thread.

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. SPI code may be used to terminate whole process tree.