On Oct 8, 2008, at 1:55 PM, Joe Bohn wrote:
Jason Warner wrote:Thanks for the explanation, David. I don't disagree with anything you've explained, but I'm not sure you've addressed my concern about the disparity in the effort required to deploy a custom valve on tomcat and on geronimo. Even with the a streamlined process involving a tomcat server portlet and using the tomcat6 plugin as a base, the user still has to become a plugin developer to deploy their valve on geronimo. If that's how it has to be, then I suppose that's how it has to be. I'm just concerned that it could turn off users that might have otherwise lived happily with geronimo. I'm not really sure how widespread the use of custom valves are, though, so maybe it's just a small minority this would even effect. I'd be curious to get some feedback from some other developers and see if they have any thoughts on the matter. Anyone else out there keeping an eye on this thread?I've been keeping an eye on it and I agree with you Jason that there is a disparity in the work required to add a valve to tomcat versus that required to add a valve to tomcat embedded in Geronimo. I also agree with David that the current Tomcat process does not lend itself to a reproducible configuration.In cases like this I tend to think like a politician and advocate a both/and rather than an either/or. I suspect that some users will want things in Geronimo to be as similar to Tomcat as possible ... and so will want a simple configuration solution. Doing so might convince them to move over to Geronimo and over time they may gain a greater appreciation for a more Geronimo like solution. Others might be coming in with more knowledge of Geronimo and expect something that is more consistent with Geronimo and can be reproduced. Can we give them both what they want?It seems like we could help the Tomcat centric folks with a simple configuration attribute that we can use to extend the classpath. For the more sophisticated Geronimo user we can direct them to rebuild/redeploy the Tomcat module with the additional dependency on the valve jar ... perhaps using c-m-p and then their own custom assembly. Even while providing the first approach we can highly recommend the second approach.It seems to me that the attribute/classpath extension is a simple thing to implement and will provide a high level of value to users that are accustomed to Tomcat. The Tomcat module rebuild/redeploy is just a matter of documentation ... correct?
I guess I'm trying to argue that we should be making doing the "right thing" as easy as modifying tomcat to have a custom valve.
I'm not convinced we're all that far off: tomcat -stop server geronimo - server restart may be needed later. tomcat - add jar to server/lib (?) geronimo - add jar to repository tomcat - edit server.xml geronmo -edit tomcat6 plam.xmlgeronimo - add artifact-alias (this could probably be automated into part of the next step). Basically this should be editing the geronimo- plugin.xml.
geronimo - deploy modified tomcat6 plan.xml, resulting in a new plugin. tomcat - restart geronimo - restart tomcat-dependent plugins/appsThere's basically only one more step in geronimo. I'm not sure how well the "obsoletes" functionality works at the moment but ideally we could have the new plugin obsolete the original and so installing it would shut down the old one, shut down the plugins depending on it, and restart the dependencies after install. This is the same number of steps.
One missing bit here is that there is no good way to deploy an app with an external geronimo-plugin.xml to end up immediately with a plugin.
thanks david jencks
JoeOn Wed, Oct 8, 2008 at 2:25 PM, David Jencks <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:On Oct 8, 2008, at 11:04 AM, Jason Warner wrote:I'm not sure if these steps are reasonable from a purely user perspective. When using plain old tomcat, you can download a binary, add your custom valve jar, make a config change and then use your server with its custom valve. To accomplish the same task in geronimo, we are asking the user to download and install maven as well as grab source code for the tomcat plugin. I'd really like to have a way we can accomplish the same goal while allowing the users to maintain a user level of interaction with geronimo.I think (1) is really a more realistic approach philosophically so I'll only discuss it more.Lets consider the results of the modifications on tomcat and geronimo. In tomcat, the user has modified their server installation and has no built-in record of what they did. If they install another serversomewhere else they have to look in their notes or try to remember what they did or ??? to get the same result. In geronimo + maven they have a reproducible and automated way to generate the customization that is suitable for storing in scm, auditing, running through qa, etc etc.Its also possible to fish the plan out of the tomcat6 plugin, modifyit a bit, and deploy it using gshell or (if you didn't start it) using the console. I think you could add the geronimo-plugin.xml using the admin console and add the artifact-aias. This on export would result in a reusable plugin. I'm not sure if you could turn around and install the plugin on the server it was generated on toinstall the artifact alias so on the next startup you'd get the newtomcat plugin. My philosophical objection to adding valves to the existing tomcatconfig is that you've changed it in a fundamental way so you should have a new, replacement, plugin instead. By this point you can addthe extra jar(s) anyway as dependencies. Maybe we could have a tomcat server portlet that would help with generating tomcat server plans with custom valves and connectorsand such stuff. I think that right now that is still the hardest part.thanks david jencksOn Wed, Oct 8, 2008 at 1:22 PM, David Jencks <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote: On Oct 8, 2008, at 7:45 AM, Jason Warner wrote:David, Could you describe to me in a little more detail what youwere thinking in regards to defining a new tomcat server in a child classloader? I'm still working on creating an example,but I found some documentation confirming tomcat's use of a TCCL in loading components and would like to continue the discussion. It seems you are proposing that a user create aplugin that defines a new tomcat instance that includes theircustom valve. Am I understanding correctly? I've taken a look at the app-per-port sample you described and this does not seem like a trivial task.app-per-port is complicated by the additional features there of:- only one artifact (an ear) instead of 2 or 3 plugins - starting the connectors after the web app has started If neither of these features is needed you can just build a plugin with the tomcat server + custom valve. There are two strategies: 1. replace the tomcat6 plugin 2. use the (stopped) tomcat6 plugin as a parent for the new plugin. In either case I'd build the new plugin with maven and start by copying the tomcat6 plugin and renaming it appropriately. Then modify the plan to include the custom valve.for (1), you'd just add the jar with the custom valve as a pomdependency. Use an artifact-alias so your tomcat plugin will replace the usual tomcat6 plugin. for (2), you'd replace the pom dependencies with a dependency on the tomcat6 plugin, and add the custom valve jardependency. In the c-m-p configuration you'll want to specifythe import on the tomcat^ plugin as "classes" so it wont get started. An artifact alias won't work here so don't deploy things that depend on tomcat6 as that will result in the tomcat6 plugin starting and having port conflicts with your plugin. Building a custom server including your plugin or installing it on a framework server via gshell is likely to work better than trying to replace the tomcat6 plugin while it's running through the admin console. hope this helps david jencksThanks, On Mon, Oct 6, 2008 at 3:08 PM, Jason Warner <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote: On Mon, Oct 6, 2008 at 1:59 PM, David Jencks <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote: On Oct 6, 2008, at 10:35 AM, Jason Warner wrote:On Mon, Oct 6, 2008 at 11:56 AM, David Jencks <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote: On Oct 6, 2008, at 7:22 AM, Jason Warner wrote:On Fri, Oct 3, 2008 at 6:55 PM, David Jencks <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote: On Oct 3, 2008, at 12:51 PM, Jason Warner wrote:Hey all. I'm working on an idea for allowing custom valves to be defined inconfig.xml. Currently this isn't possiblesince the tomcat classloader would notcontain the custom classes for the valve. I've create a jira for tracking this issue[1] and it contains a few links toworkarounds. IMHO, The solution we shouldbe looking for is a way to add classes to a module without having to undeploy,modify the module config, and redeploying.People have suggested stuff like this before. IMO it pretty much goes against the fundamental idea of geronimo of having fairly fixed plugins with only a few knobs to turn to adjust things in config.xml and config-substitutions.properties.Why is changing the classloader contents inconfig.xml a good idea? What is so hard about redeploying the app if you want to change its classloader significantly? If you want to change a class in the app you have to redeploy it.... why is this situation different? The specific instance I have in mind for thischange is using a custom valve for tomcat, so Ithink the scope really should be limited to just the tomcat module. I can't think ofanother instance where this would be useful, soit's probably not necessary or desirable toexpand it further. I believe this situation isdifferent because the structure of geronimo is causing a disconnect between the functionalityof tomcat and the functionality of tomcat as itis embedded in geronimo. As Don just said in the middle of my typing this, I don't believe we should expect the average user to have to rebuild one of our modules to add something that can be added in a much simpler way within tomcat itself.Could you explain more about the circumstancesfor this custom valve? Is it intended to be forevery app deployed on this tomcat server instance rather than for one particular app?Will it work if it is in a child classloader ofthe tomcat plugin classloader?When a valve is added to the tomcat valve chain, it becomes part of the request processing pipeline. Every request that is made to that tomcat serverinstance passes through this valve chain as it's processed regardless of whether the valve will actupon it or not. It's possible that a single web appwill be the only app to use the valve, and for that instance it is already possible to define the valvein the context of the web app rather than the tomcatserver. We need to be able to define a valve as part of tomcat server instance as well, though, to be consistent with tomcat. Currently we can onlydefine the valves on the per web app basis. I don't think this would work in a childclassloader of the tomcat plugin classloader. When we start up the tomcat module now, the currently defined valves are processed and added to theengine. The custom valves would need to be added tothe valves already in the tomcat engine to beavailable in the way described previously. Once thevalves were added to the engine (which would be using the tomcat classloader, I believe) the classdef not found issues we currently see would pop backup. For this to work, the custom valve classes and the tomcat engine would need to share the same classloader.Could you try this to be sure? I would hope that tomcat would use a TCCL or supplied classloader for loading components rather than something like TomcatEngine.class.getClassLoader() which I believe is what you are suggesting it does. One example of an inconvenient tomcat configuration is the app-per-port sample where we set up a wholeadditional tomcat server in a child configuration. Ithink all the server components in that example are also in a standard tomcat server but its a similar situation to what I'm thinking of here in terms of configuring a tomcat server in a child classloader. Sure. It'll take me a bit as I don't actually have any examples prepared yet.At the moment I would MUCH rather see us make iteasier for users to deploynew/different/modified tomcat servers (and otherplugins) than introduce a hack to modify classloaders of existing plugins. Ourcustomization story is already too complicated,IMO we don't need to glue on more bits that don't actually fit well. IMO the best end result for users is to have anew tomcat plugin with the needed extra jars andvalve configuration. Lets look for a way to make it really easy for our users to get there. I agree that a whole new plugin with all desiredfunctionality included would be best for users. Any ideas how to make this easier than it currently is? Perhaps the attribute idea mentioned by Joe couldserve as a temporary solution until we can come up with something better. How would you deal with this in an osgi or spring environment?If anyone knows how osgi deals with situations like this I'd find it really helpful in considering alternative directions. thanks david jencksthanks david jencksThanks! thanks david jencksI think this can be done by allowing a user to indicate jars that should beloaded by a module within the config.xml. These jars can then be added to themodule's classloader for use by the module. I'm not extremely familiar with how our classloader works, but I've taken a look through the code and I think the ability to add to the classloader can beimplemented without too much difficulty. I'm not quite sure what type of scope togive this change, though. Should I leave it as a change aimed solely at tomcat valves or should it be expanded to encompass any configuration? I realize this is only a rough idea of what i plan to do, but I'm still working out thedetails of how to proceed. I'm hoping forsome feedback on what I intend to do and possibly some alternate ideas if anyone has some.< br> Thanks! [1] https://issues.apache.org/jira/browse/GERONIMO-4335 -- ~Jason Warner-- ~Jason Warner-- ~Jason Warner-- ~Jason Warner -- ~Jason Warner-- ~Jason Warner-- ~Jason Warner
