[xwiki-devs] Jetty load time analysis

Hi devs, I've been finding that Jetty takes a lot of time to start lately. So I've run some profiling on it. Starting Jetty (till the STARTING message) takes 15 seconds on my machine (in debug mode, we win 3 seconds, ie 12s start time), split like this: * 50% of the time spent scanning jars in WEB-INF/lib (JarInputStream.getNextJar()) - 7s * 10% in Jetty itself - 2s * 40% in our code in Extension Manager init (2.5s) and in Component registration from their annotations (2.5s) - 5s If I remove the start of the EM in XWikiServletContextListener, we start in 7 seconds (instead of 15s) If I try to start Jetty without any webapp, it starts in 500ms. If I remove the oldcore legacy jar (2.5MB) we win 1 second in start up time. Note: This is all before XWiki.init() is called on the first request. Analysis of ComponentAnnotationLoader (2.5s): * 1.2s just loading classes from the CL * 1s getDeclaredFields (reflection API) * 800ms initializing SLF4J Analysis of Extension Manager init (2.5s): * In DefaultCoreExtensionScanner.loadExtensions(): ** 500ms URL.toURI() ** 500ms MavenXpp3Reader.read() - POM reading ** 150ms org.Reflections scanning ** 150ms resource loading from CL (getResourceAsStream()) * In DefaultExtensionLicenseManager.initialize() ** 314ms in org.Reflections * 130ms of loading xwiki.properties Conclusion ========= * XWiki's size in number of JARs and their sizes makes it long to start Jetty. * We could make some small optimizations in EM and Component loading but we wouldn't win that much, on the order of 2s in total (i.e. 15% of total load time) Thanks -Vincent