Hi devs,
With the new 4.5.x kernel release we are upgrading the tomcat version from
7 to 9. I am currently trying to update the tomcat version to 9.0.21 in
product-is. This mail is to discuss the upgrade process.
Now the web apps got deployed and working with tomcat 9. But the management
console and the service calls are not working. This may be due to
the JspServlet customizations. I am working on it now.
We have the following customized classes of the tomcat.
- SCIRegistrarContextConfig - This class customized to process
ServletContainerInitializers in the form of jars or OSGi bundles. This
class overrides the 'processServletContainerInitializers' method in
org.apache.catalina.startup.ContextConfig class.
- CarbonTomcatRealm - This is a custom Tomcat realm that uses Carbon
realm inside.
- ExtendedStandardService - This class customized to stop starting of
the transport connectors, because we need to start the connector after all
the OSGi bundles are wired
- CarbonTomcatJarScanner - This class customized to load the TLD scanner
classes reside in the OSGi bundles during the web app loading. According to
the servlet 3.0 spec, tldScanner classes are picked up during web app
loading phase from the classPath. However, the StandardJarScanner fails to
pick up the TLD scanner classes reside in the OSGi bundles. Because in the
StandardJarScanner scan the classes if the classloader is an instance of
the URLClassLoader. But ModuleClassLoader (the OSGi classloader which is
the parent classLoader of tomcat web app class loader) is not an instance
of it.
- CarbonWebappLoader and CarbonWebappClassLoader - This customization
allows to change the classloading pattern based on the
webapp-classloading.xml file. There is room for improvements in these
classes because the common environmental libraries have been loaded for
each web app which causes memory and start-up delay. We can create a new
classloader for each environment and create the class loader hierarchy.
- JspServlet - JSPServlet wraps the Apache Jasper Servlet making it
appropriate for running in an OSGi environment under the Http Service. The
Jasper JSPServlet makes use of the Thread Context Classloader to support
compile and runtime of JSPs and to accommodate running in an OSGi
environment, a Bundle is used to provide the similar context normally
provided by the web app.
- Other classes with session-related customizations,
- CarbonTomcatSimpleTcpCluster
- CarbonSessionReplicationMessage
- CarbonTomcatClusterableSessionManager
- CarbonTomcatSessionMessage
- CarbonTomcatSessionManager
- CarbonTomcatSessionPersistentManager
We also have the following patched classes of the tomcat,
- org.apache.catalina.startup.ExpandWar : Patch to unpack web apps of
tenants inside the tenant's webapps/ directory. This needs to be refactored
with the new improvements done in the tomcat 9.
- org.apache.coyote.RequestInfo : Patch to record bandwidth statistics
data. There are some new methods added need to refactor.
I have done the necessary changes in the
SCIRegistrarContextConfig, ExtendedStandardService,
CarbonTomcatJarScanner, CarbonWebappLoader and CarbonWebappClassLoader to
support tomcat 9. As mentioned above the classloading customizations can be
improved. IMO, we can look into it once we completely upgrade and stables
the products with tomcat 9. Currently, I am working on the JspServlet to
fix the JSP issues. Next, I have planned to work in the patched classes and
then in other session-related customizations.
Other than these, tomcat 9 also has new features like HTTP/2 support, TLS
virtual hosting and multiple certificate support for connectors. We can
also look into the possibilities of using these new features as well. We
tomcat 9 have contains configuration changes. I will update this mail with
the list of config changes.
Thanks,
Senthalan
--
Senthalan Kanagalingam | Software Engineer | WSO2 Inc.
(m) +94 (0) 77 18 77 466 | (w) +94117435800 | (e) [email protected]
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