geronimo-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Bruce Snyder <fer...@frii.com>
Subject Re: online and offline deployment
Date Sun, 07 Nov 2004 18:21:13 GMT
Aaron Mulder wrote:

> 	Just to reiterate, I think Jeremy is saying that using the 
> deployer tool for offline install is limited because it doesn't know what 
> GBeans the server is using for the ConfigStore and PersistentConfigList 
> and so on.  If we instead actually start the server to do an "offline" 
> deployment/installation, then all the corrct GBeans will be running and 
> that is no longer an issue.
> 
> 	An alternative would be for the deployer to inspect the server's 
> configuration when it starts, and load every dependency from the 
> immediate parent of the module to be deployed up through the "root", and 
> that should identify the correct ConfigStore and PersistentConfigList.
> But this is tricky too, since how would it know what ConfigStore to load 
> the configurations out of (including the configuration for the 
> ConfigStore, aargh!).  In the end, I suspect this depends on how 
> server.jar was packaged, and if you plan to start your server with 
> start-my-server.jar instead of server.jar then I don't know how the 
> deployer would know that, so I don't know where it would get the original 
> ConfigStore reference from -- perhaps we'd need to give it an option to 
> identify your server startup JAR.  But I think this would still fail if 
> the server was running (since you'd probably clash for ports trying to 
> load some of the services between ConfigStore and application), so it's an 
> "offline" deploy in name only.
> 
> 	Another option is that we can provide a tool that works 100% for
> the default server configuration (LocalConfigStore+FileConfigurationList).  
> But it would not work in the face of customizations to the 2 core
> components: if you swap out your LocalConfigStore, then the tool would not
> work (it would install into the wrong place), and if you swap out your
> PersistentConfigurationList then the tool would be unable to mark any
> module to be started.  If we wanted to, we could make offline deploy tools 
> available for different combinations of those GBeans, or give you a 
> procedure to build a new deploy tool from an old one.
> 
> 	The main reason I feel that this is important is that most other
> products support it.  Generally if you copy a new EAR over an old one
> while the server is not running, and then start the server, the new
> version of the EAR will deploy on startup.  (Tomcat 5 in the one I can
> think of that doesn't do this).  I just hate to tell people that things 
> that used to work won't work any more if they move to Geronimo.  On the 
> other hand, I think this behavior was mostly implemented via a hot deploy 
> directory, so if we provide a GBean for a hot deploy directory, then maybe 
> we don't need a offline deploy tool at all (beyond for building the 
> server).
> 
> 	And I guess the last issue is related.  In the long run, it will
> be nice/necessary to have some kind of packaged-configuration-handling
> features, in the deploy tool or another tool:
>  - extract a CAR file from an entry in a server's ConfigStore
>  - sign a CAR file (either in the server's ConfigStore or as a file)
>  - transfer a packaged configuration directly from one server to another
>  - deploy a CAR file into a server
> 
> Aaron
> 
> On Sat, 6 Nov 2004, Jeremy Boynes wrote:
> 
>>As promised Thursday, here are the details of my concerns about mixing
>>offline and online deployment.
>>
>>My concerns on this issue stem from how we package GBeans together for
>>use by the kernel. Rather than handling them one-by-one, Geronimo uses
>>the notion of a pre-canned Configuration which contains a number of
>>GBean instances and the classpath information needed to load them.
>>Configurations can be loaded by the kernel and when started bring all
>>the GBeans they contain online together.
>>
>>A key feature of Configurations is they are portable between different
>>Geronimo installations - specifically a Configuration can run in any
>>Geronimo kernel that can resolve its dependencies. This is less critical
>>for the single-server mode we have now but is very important as Geronimo
>>scales to clustered or grid configurations - it allows us to efficiently
>>move applications between the servers on demand.
>>
>>This also has benefits where change management is important, such as
>>business critical installations. For example, a Configuration can be
>>built and signed in a test or integration environment and moved
>>*provably unchanged* though the test, stage and release to production
>>process. Alternatively, an OEM can release an application to channel as
>>a signed Configuration, end-users can have the assurance it has not been
>>tampered with, and the OEM can reduce costs by reducing problems caused
>>by variations in the end-user environment.
>>
>>In the kernel, the process of loading and unloading Configuration is
>>handled by a ConfigurationManager that uses ConfigurationStores to store
>>them. The store exposes a simple API for installing and uninstalling
>>Configurations and for retrieving them so they can be loaded. We have a
>>simple LocalConfigStore implementation that uses the local filesystem to
>>store them; other implementations are possible using different
>>persistence approaches such as databases, LDAP or proprietary
>>configuration management systems.
>>
>>
>>The deployment system in Geronimo is the interface between user-domain
>>artifacts such as J2EE modules (EARs, WARs, etc.) or deployment plans
>>and the configuration management system described above. It essentially
>>combines modules with plans and generates Configurations.
>>
>>It comprises three parts:
>>* External interfaces such as the command line tool, console or JSR-88
>>   provider that get the modules and plans from the user
>>* ConfigurationBuilders such as EARConfigBuilder and
>>   ServiceConfigBuilder that do the combination and produce the target
>>   Configuration
>>* Back-end interfaces that store the Configuration either in a
>>   ConfigurationStore or as an output file
>>
>>The ConfigurationBuilders are GBeans and run inside a Geronimo kernel.
>>Apart from ease of implementation, they also have access to the
>>resources provided by that system - for example, they can use the
>>Repository to load classes during processing, and they can use the
>>ConfigurationManager to load other Configurations that the target may be
>>dependent on.
>>
>>
>>To support online deployment, we run a deployment system inside the same
>>kernel as the J2EE server - it is actually part of the
>>org/apache/geronimo/Server Configuration although work is progress to
>>allow it to be run as a separate dependent configuation.
>>
>>The JSR-88 provider interacts with this deployment system to fulfill the
>>spec requirements for distribute, start, stop, undeploy etc. For
>>example, during a distribute operation the module and plan are passed to
>>the deployment system, it uses an EARConfigBuilder to produce the output
>>Configuration, which it then installs in the target ConfigurationStore.
>>A JSR-88 start operation causes the Configuration to be loaded from the
>>store and then started.
>>
>>
>>However, this leaves us with a chicken-and-egg problem. The online
>>deployment system above is itself part of a configuration - how do we
>>build that configuation?
>>
>>To solve this, and because it seemed generally useful, we built a
>>standalone offline deployment system. Run from the command line, this
>>would take module + plan and produce a Configuration. To reuse as much 
>>of the configuration building infrastructure as possible, it boots an
>>embedded Geronimo kernel and loads a Configuration containing just the
>>deployment system. As a running kernel, it also provides access to a
>>Repository and ConfigurationStore that the ConfigurationBuilders can use
>>to resolve dependencies (including dependencies on other
>>Configurations). However, these are *its* Repository and
>>ConfigurationStores and *not* those from the target server.
>>
>>To cheat our way around the chicken-and-egg problem we took the simple
>>but expedient solution of having the standalone deployer and the default
>>server use the same type and location of store and repository. Then, by
>>simply telling the standalone deployer to install a configuration into
>>its own store it would also be available to the default server
>>configuration. This is a hack, pure, simple and effective.
>>
>>When we introduce any additional complexity into the situation, then
>>this hack starts to break down. For example, if the user adds a
>>database-based ConfigurationStore to the server (for example, to make
>>GBean state persistence more reliable) then the standalone deployer
>>would not be able to install the generated Configuration into that store.
>>
>>
>>All things considered, I think having options in the standalone deployer
>>that rely on it sharing the same type and location of Repository and
>>ConfigurationStore will lead to obscure behaviour and strange behaviour
>>as soon as we progress beyond the most basic default configuration. That
>>is why I voted at the start for "2 simple tools rather than one complex
>>one."  Going further as has been proposed and coupling the standalone
>>deployer to the internal implementation of the
>>PersistentConfigurationList seems like pouring gasoline on the fire.
>>
>>I have been portrayed on this list as being alone in my opinion but I
>>will point out that in the initial vote Eric LeGoff, Aaron Mulder and
>>David Jencks also voted for 2 tools (as opposed to Peter Lynch, Davanum
>>Srinivas, Hiram Chirino and Bruce Snyder who voted for one); Dain
>>Sundstrom voted for one tool, but wanted another to support the
>>functionality we have to output Configurations as jars ("that is another
>>tool for another day" but we need it now to build the server) which
>>sounds like two tools to me.
>>
>>After that vote, Aaron proposed and attained consensus for a single
>>tool. The syntax is simple enough and mirrors the JSR-88 API making it
>>ideal for online deployment (which is all JSR-88 supports).
>>
>>However, during implementation Aaron ran into the issues described above
>>and on the thread from 11/4/04 when trying to support the offline mode
>>not covered by JSR-88. These are clearly technical issues which we need
>>to resolve. To facilitate that, Aaron proposed to commit his work so
>>that all could see and discuss; he and I were promptly and unjustifiably
>>  flamed by some members of the community.
>>
>>Since Thursday he has committed this code and I think we need to review 
>>where we are. My belief is that the online side is fully implemented, 
>>that the standalone deployer works as before (package option), and the 
>>big remaining issue is the one described above where someone is trying 
>>to "deploy" applications to an offline server.
>>
>>In this message
>>
>>http://nagoya.apache.org/eyebrowse/ReadMsg?listName=dev@geronimo.apache.org&msgNo=9696
>>
>>I wrote that you could distribute to your heart's content; this was
>>wrong. The discussion with Aaron highlighted that the problem about
>>store type and location applies to distribute as well as the other
>>operations. It looks like the only thing you can reliably do offline is
>>package a Configuration for later use.
>>
>>I would suggest then, rather than the --add option I proposed for the
>>server we instead have a --install option which boots the server,
>>restarts all previously running configs and installs the new one. The
>>offline usage would then be:
>>
>>java -jar deployer.jar package foo.war foo-plan.xml foo.car
>>java -jar server.jar --install foo.car
>>
>>This also provides a simple mechanism for deploying once and running 
>>everywhere: the output configuration can be installed in multiple places 
>>as easily as one.
>>
>>The issue with this is that it fits the admin's view better than the
>>developer's. However, I continue to believe the:
>>
>>   start server
>>   repeat
>>      write code
>>      build (with distribute/start to online server)
>>      test
>>   until app works or it's time to go home
>>
>>cycle is what most developers use and that Aaron's changes (in
>>conjunction with the existing Maven plugin) have made it easy for them
>>to work that way. They are not really interested in fancy offline
>>deployment tricks.
>>
>>To support carrier-grade configuration management, clustered and grid
>>environments and OEMs, I believe we need an effective way of generating
>>pre-packaged configurations using requires Maven/Ant plugins
>>that can be used in the release process, tools like Aaron's that an
>>administrator can use from the command line, and mechanisms for
>>installing them in and for transporting them between between servers.
>>
>>I think we are very close to achieving this and if we can address these
>>last issues then Geronimo will be acceptable to both the developer
>>community and to serious IT decision makers.

I spent part of last night and part of this morning re-reading all of 
this info to better understand the dilemma over the deploy tool. After 
reading these two messages a couple times I feel like I understand the 
issues at hand far better than when I cast my vote.

I'm sure that others will find themselves with the same quandary I 
currently have, whereby upon further education of the issues surrounding 
the deployment tool, I wish I could recast my vote. If others do, in 
fact, have the same sentiment, then I propose that the deploy tool vote 
be recalled and we start a fresh vote on the same topic, or, I just 
change my vote. Does anyone else feel this way?

Bruce
-- 
perl -e 'print 
unpack("u30","<0G)U8V4\\@4VYY9&5R\\"F9E<G)E=\\$\\!F<FEI+F-O;0\\`\\`");'

The Castor Project
http://www.castor.org/

Apache Geronimo
http://geronimo.apache.org/

Mime
View raw message