1 / 27

GATE development hints

GATE development hints. Reporting bugs Submitting a patch The user guide Continuous integration. Bugs, feature requests. Use the tracker on SourceForge http://sourceforge.net/projects/gate/support Give as much detail as possible

quilla
Télécharger la présentation

GATE development hints

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GATE development hints • Reporting bugs • Submitting a patch • The user guide • Continuous integration

  2. Bugs, feature requests • Use the tracker on SourceForge • http://sourceforge.net/projects/gate/support • Give as much detail as possible • GATE version, build number, platform, Java version (1.5.0_15, 1.6.0_03, etc.) • Steps to reproduce • Full stack trace of any exceptions, including "Caused by…" • Check whether the bug is already fixed in the latest nightly build

  3. Patches • Use the patches tracker on SourceForge • Best format is an svn diff against the latest subversion • Save the diff as a file and attach it, don't paste the diff into the bug report. • We generally don't accept patches against earlier versions

  4. Patches (2) • GATE must compile and run on Java 5 • Not sufficient to set source="1.5" and target="1.5" but compile on Java 6 • This doesn't prevent you calling classes/methods that don't exist in 5 • Test your patch on Java 5 before submitting

  5. The User Guide • Everything in GATE is (theoretically) documented in the GATE User Guide • http://gate.ac.uk/userguide • Every change to the core should be mentioned in the change log • http://gate.ac.uk/userguide/chap:changes • User guide is written in LaTeX

  6. Updating the user guide • Lives in subversion • https://gate.svn.sourceforge.net/svnroot/gate/userguide/trunk • Build requires pdflatex, htlatex (tex4ht package), sed, make, etc. • On Windows, use Cygwin • Download http://gate.ac.uk/sale/big.bib and put in directory above the .tex files

  7. Updating the user guide (2) • Edit the .tex files • Graphics, screenshots, etc. should be .png • Check in changes to .tex files, the PDF and HTML are regenerated automatically by…

  8. Hudson • Continuous integration platform • Automatically rebuilds GATE and user guide (among others) whenever they change • Also does a clean build of GATE every night • Nightly builds published at http://gate.ac.uk/download/snapshots

  9. Hudson • Junit test results available for each build • http://gate.ac.uk/hudson

  10. Running GATE Embedded in Tomcat (or any multithreaded system) Issues and tricks

  11. Introduction • Scenario: • Implementing a web service (or other web application) that uses GATE Embedded to process requests. • Want to support multiple concurrent requests • Long running process - need to be careful to avoid memory leaks, etc. • Example used is a plain HttpServlet • Principles apply to other frameworks (struts, Spring MVC, Metro/CXF, Grails…)

  12. Setting up • GATE libraries in WEB-INF/lib • gate.jar + JARs from lib • Usual GATE Embedded requirements: • A directory to be "gate.home" • Site and user config files • Plugins directory • Call Gate.init() once (and only once) before using any other GATE APIs

  13. Initialisation using a ServletContextListener • ServletContextListener is registered in web.xml • Called when the application starts up <listener> <listener-class>gate.web..example.GateInitListener</listener-class> </listener> public void contextInitialized(ServletContextEvent e) { ServletContext ctx = e.getServletContext(); File gateHome = new File(ctx.getRealPath("/WEB-INF")); Gate.setGateHome(gateHome); File userConfig = new File(ctx.getRealPath("/WEB-INF/user.xml")); Gate.setUserConfigFile(userConfig); // site config is gateHome/gate.xml // plugins dir is gateHome/plugins Gate.init(); }

  14. GATE in a multithreaded environment • GATE PRs are not thread-safe • Due to design of parameter-passing as JavaBean properties • Must ensure that a given PR/Controller instance is only used by one thread at a time

  15. First attempt: one instanceper request • Naïve approach - create new PRs for each request public void doPost(request, response) { ProcessingResource pr = Factory.createResource(...); try { Document doc = Factory.newDocument(getTextFromRequest(request)); try { // do some stuff } finally { Factory.deleteResource(doc); } } finally { Factory.deleteResource(pr); } } Many levels of nested try/finally: ugly but necessary to make sure we clean up even when errors occur. You will get very used to these…

  16. Problems with this approach • Guarantees no interference between threads • But inefficient, particularly with complex PRs (large gazetteers, etc.) • Hidden problem with JAPE: • Parsing a JAPE grammar creates and compiles Java classes • Once created, classes are never unloaded • Even with simple grammars, eventually OutOfMemoryError (PermGen space)

  17. Second attempt: using ThreadLocals • Store the PR/Controller in a thread local variable private ThreadLocal<CorpusController> controller = new ThreadLocal<CorpusController>() { protected CorpusController initialValue() { return loadController(); } }; private CorpusController loadController() { //... } public void doPost(request, response) { CorpusController c = controller.get(); // do stuff with the controller }

  18. Better than attempt 1… • Only initialise resources once per thread • Interacts nicely with typical web server thread pooling • But if a thread dies, no way to clean up its controller • Possibility of memory leaks

  19. A solution: object pooling • Manage your own pool of Controller instances • Take a controller from the pool at the start of a request, return it (in a finally!) at the end • Number of instances in the pool determines maximum concurrency level

  20. Blocks if the pool is empty: use poll() if you want to handle empty pool yourself Simple example private BlockingQueue<CorpusController> pool; public void init() { pool = new LinkedBlockingQueue<CorpusController>(); for(int i = 0; i < POOL_SIZE; i++) { pool.add(loadController()); } } public void doPost(request, response) { CorpusController c = pool.take(); try { // do stuff } finally { pool.add(c); } } public void destroy() { for(CorpusController c : pool) Factory.deleteResource(c); }

  21. Exporting the grunt work -the Spring Framework • Spring Framework • http://www.springsource.org/ • Handles application startup and shutdown • Configure your business objects and connections between them using XML • GATE provides helpers to initialise GATE, load saved applications, etc. • Built-in support for object pooling • Web application framework (Spring MVC) • Used by other frameworks (Grails, CXF, …)

  22. Initialising GATE with Spring <beans xmlns="http://www.springframework.org/schema/beans" xmlns:gate="http://gate.ac.uk/ns/spring"> <gate:init gate-home="/WEB-INF" plugins-home="/WEB-INF/plugins" site-config-file="/WEB-INF/gate.xml" user-config-file="/WEB-INF/user-gate.xml"> <gate:preload-plugins> <value>/WEB-INF/plugins/ANNIE</value> </gate:preload-plugins> </gate:init> </beans>

  23. Loading a saved application • scope="prototype" means create a new instance each time we ask for it • Default is singleton - one and only one instance <gate:saved-application id="myApp" location="/WEB-INF/application.xgapp" scope="prototype" />

  24. Spring servlet example • Spring provides HttpRequestHandler interface to manage servlet-type objects with Spring • Declare an HttpRequestHandlerServlet in web.xml with the same name as the Spring bean

  25. Spring servlet example • Write the handler assuming single-threaded access • Will use Spring to handle pooling for us public class MyHandler implements HttpRequestHandler { public void setApplication(CorpusController app) { ... } public void handleRequest(request, response) { Document doc = Factory.newDocument(getTextFromRequest(request)); try { // do some stuff with the app } finally { Factory.deleteResource(doc); } } }

  26. Tying it together • web.xml <!-- set up Spring --> <listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener> <!-- servlet --> <servlet> <servlet-name>mainHandler</servlet-name> <servlet-class> org.springframework.web.context.support.HttpRequestHandlerServlet </servlet-class> </servlet>

  27. Tying it together (2) • applicationContext.xml <gate:init ... /> <gate:saved-application id="myApp" location="/WEB-INF/application.xgapp" scope="prototype" /> <bean id="myHandlerTarget" class="my.pkg.MyHandler" scope="prototype"> <property name="application" ref="myApp" /> </bean> <bean id="handlerTargetSource" class="org.springframework.aop.target.CommonsPoolTargetSource"> <property name="targetBeanName" value="myHandlerTarget" /> <property name="minIdle" value="3" /> <property name="maxIdle" value="3" /> <property name="whenExhaustedActionName" value="WHEN_EXHAUSTED_BLOCK" /> </bean> <bean id="mainHandler" class="org.springframework.aop.framework.ProxyFactoryBean"> <property name="targetSource" ref="handlerTargetSource" /> </bean>

More Related