That sounds good. If you havent already it will be important to become familiar with OSGi and Sling itself. Please dont do too much work before getting being accepted. I cant guarantee that you will be accepted since there are lots of Apache projects, lots of submissions and a limited number of places given to Apache.
Have a great weekend. Ian On 7 April 2013 02:12, Dishara Wijewardana <[email protected]> wrote: > Hi Ian > Than you for the quick response. I have started localhost Cassendra and > written some codes through hector API to create columns and etc. And works > fine. I am still doing some more test codings to get familiar more with > Cassendra these days so that I can reuse those codes and write an > appropriate CassendraResourceProviderUtil class .Meanwhile I will prepare > the project proposal. Please let me know if you want something more/else > to be done before hand that would be useful to this project. > > On Sat, Apr 6, 2013 at 12:45 PM, Ian Boston <[email protected]> wrote: > > > Hi > > Hector looks good. > > > > Sling wont ship a Cassandra instance, for this project it will uses a > > Cassandra instance setup separately Last time I spun up Cassandra it for > > dev purposes it was just as easy as installing MySQL or PostgreSQL, so I > > think that fine. > > > +1. > > > > > If using Hector, I think it would be good to do everything in CQL and > keep > > it all very simple and transparent. Remember the aim of the project is to > > prove that the ResourceProvider API can support Cassandra as a repository > > store, and that API is complete and usable all the way through to the > > latest security related APIs that have just been developed. This project > is > > not an exercise in doing cool and complex things in Cassandra > > with automated ORM mapping that binds the code forever to one Cassandra > > API. > > > > > Totally agree. So ideally in a users's perspective, when dealing with sling > layer, there should not be any difference between the resources in > /root/jackrabbit and /root/cassandra for example. > > Sound ok to you, or do you see problems ? > > > > Yes, no problems at all. Quite fine with the suggestions. > > > Ian > > > > > > On 6 April 2013 16:55, Dishara Wijewardana <[email protected]> > > wrote: > > > > > Hi Ian, > > > > > > In Sling, are we going to ship native Cassandra instance with the sling > > > binary pack? ( is there already a native cassandra server starting at > > sling > > > server start up ?) > > > I am willing to use hector API to deal with Cassandra, as in most of > > > occasions around . Please let me know if there is any concerns on that > > > aspect ? > > > > > > > > > On Thu, Apr 4, 2013 at 1:04 AM, Dishara Wijewardana < > > > [email protected] > > > > wrote: > > > > > > > Hi Ian, > > > > > > > > On Tue, Apr 2, 2013 at 4:44 AM, Ian Boston <[email protected]> wrote: > > > > > > > >> On 2 April 2013 07:55, Dishara Wijewardana <[email protected] > > > > > >> wrote: > > > >> > Hi Ian, > > > >> > Thanks for the explanation. Really helped me to get several stuff > > > >> cleared. > > > >> > > > > >> > On Mon, Apr 1, 2013 at 7:57 AM, Ian Boston <[email protected]> wrote: > > > >> > > > > >> >> Hi Dishara, > > > >> >> > > > >> >> You should not think about implementing the JCR API classes > > > >> >> (javax.jcr.*). You should think about implementing the Resource > > > >> >> API[1]. When you need to perform something that the ResourceAPI > > > doesnt > > > >> >> support (say in a servlet), then you can use the > > > >> >> Resource.adapTo(Class<?> clazz) method to adapt the resource > into a > > > >> >> class that supports that operation. > > > >> >> > > > >> > > > > >> > Interesting.!! . If I got you correctly "adapTo" concept used to > > > achieve > > > >> > *kind of* dynamic multiple inheritance rather than extending a > heavy > > > >> > abstract class. if that is so, this is a wonderful idea and I > really > > > >> like > > > >> > the concept. > > > >> > > > >> Calling it inheritance might be going too far as the class isn't > > > >> necessarily the same, but in essence, yes. > > > >> > > > >> > > > > >> > > > > >> >> > > > >> >> eg: > > > >> >> The properties of the resource are exposed via ResourceMetadata > > [2], > > > >> >> but lets say you want to find the underlying Cassandra object to > > copy > > > >> >> it and create a child. > > > >> >> > > > >> >> So: CassandraResource implements Resource, which is what is > > returned > > > >> >> when the CassandraResourceProvider resolves a Resource. A client > > > >> >> should not bind to CassandraResource or mention it, since its > > almost > > > >> >> certainly an implementation and not an API. However, the > Cassandra > > > >> >> bundle you have written also implements CassandraContent which > has > > > >> >> CassandraContent.copy(String copyLocation) and > > > >> >> CassandraContent.createChild(String childName). > > > >> > > > > >> > To get to this you would do > > > >> >> CassandraResource.adaptTo(CassandraContent.class) > > > >> >> BTW, CassandraContent.class is an API exported by your bundle. > > > >> >> > > > >> > > > > >> > If I got you correctly, > > > >> > after CassandraResource.adaptTo(CassandraContent.class) I should > be > > > >> able > > > >> > to call > > > >> > CassandraResource.copy(String copyLocation) > > > >> > and CassandraResource.createChild(String childName). > > > >> > > > > >> > Then I will have to write an "Adaptable" class to > > > >> > facilitate CassandraResource to deal with its corresponding > > cassandra > > > >> > nodes. > > > >> > In that sense I feel the best way to approach to this project when > > > >> > implementing is an bottom-up approach. We start from the > "Adaptable" > > > >> class > > > >> > (given the fact that it should be expanded during implementation) > > and > > > >> then > > > >> > goes to the sling Resource wrapper layer which is > > > CassandraResourceImpl. > > > >> > > > >> > > > >> Resource extends Adaptable, so you dont get much choice there, just > > > >> implement the resource. > > > >> > > > >> > > > > >> > What do you think ? And may I know the expected scope of this > > project > > > by > > > >> > the community (just a potential one, during the implementation we > > can > > > >> > expand it as time permits) .i.e > > > >> > READ, > > > >> > READ with access control > > > >> > READ/WRITE with access control and etc. > > > >> > > > > >> > > > >> Yes, thats the idea. > > > >> It would be nicer to have 4 iterations to fit the GSoC timeline and > do > > > >> 2 before half time, and 2 after. Perhaps the first half can also > > > > > > > > include spinning up Cassandra, getting client APIs working and > getting > > > >> fully upto speed with that area of Sling. > > > >> > > > > > > > > +1 . Will make in to four iteration (generally 2 before midterm and 2 > > > > after mid term) and will include getting client API working for > > Cassandra > > > > and related sling stuff as a part of first two iterations (which > means > > > > before mid term ). And to meet deadlines, should target more to be > > > > completed before mid term compared to the work scheduled after the > mid > > > > term. Will make it count in project proposal time line schedule. And > > > thank > > > > you for the aforementioned feedback so that I can provide a solid > > > proposal > > > > in this year as well. > > > > Will post as soon as when I got update. Meanwhile I will build sling > > and > > > > getting familiar with the code base with the help of the sling > > > > documentation. > > > > > > > > > > > >> > > > >> > > > >> Ian > > > >> > > > > >> >> I hope that gives you an idea of how a CassandraResourceProvider > > and > > > >> >> associated implementation should work. If you havent already, and > > are > > > >> >> still interested you should read up on how Sling and OSGi works. > > > >> >> Trying the "Sling in 15 minutes"[3] is a good place to start. And > > > then > > > >> >> reading everything you can about Declarative Services in OSGi. > The > > 2 > > > >> >> key things you are going to need to understand is how OSGi > bundles > > > >> >> import and export packages and then how Declarative, declare > > services > > > >> >> that they depend on and declare services they implement, [4] is a > > > >> >> bunch of links. > > > >> >> > > > >> > > > > >> > Yes, I will go through the mentioned links. Specially like [3] > > which I > > > >> have > > > >> > not yet gone through. I also have some experience in using OSGi > > > >> importing > > > >> > exporting packages and using maven scr plugin in classes with > "bind" > > > >> > "unbind" attributes to register and unregister OSGi services and > > etc. > > > >> > > > > >> > > > > >> >> HTH > > > >> >> Ian > > > >> >> > > > >> >> > > > >> >> 1 > > > >> >> > > > >> > > > > > > http://sling.apache.org/apidocs/sling6/org/apache/sling/api/resource/Resource.html > > > >> >> 2 > > > >> >> > > > >> > > > > > > http://sling.apache.org/apidocs/sling6/org/apache/sling/api/resource/ResourceMetadata.html > > > >> >> 3 http://sling.apache.org/site/discover-sling-in-15-minutes.html > > > >> >> 4 http://www.osgi.org/download/r4v42/r4.cmpn.pdf (chapter 112) > > > >> >> > > > >> >> > > > >> > > > > > > http://felix.apache.org/documentation/subprojects/apache-felix-maven-scr-plugin/scr-annotations.html > > > >> >> > > > >> >> > > > >> > > > > > > http://felix.apache.org/documentation/subprojects/apache-felix-maven-scr-plugin/extending-scr-annotations.html > > > >> >> > > > >> >> On 31 March 2013 21:58, Dishara Wijewardana < > > [email protected] > > > > > > > >> >> wrote: > > > >> >> > Hi Ian, > > > >> >> > Thank you very much for the explanation. Before replying to > this > > > >> mail, I > > > >> >> > revisited the facts you mentioned and try to comeup with a end > to > > > >> end big > > > >> >> > picture and what are the challenges that has to face when > > > >> implementing > > > >> >> this > > > >> >> > project. > > > >> >> > > > > >> >> > Read/write with Cassandra data seems is pretty straight forward > > > with > > > >> few > > > >> >> > lines of code using a client API. But the tricky part is to > make > > a > > > >> clean > > > >> >> > bridge between JCR wrapped sling resource API vs Cassendra > column > > > >> family > > > >> >> > data storage. So I took some time and went through the JCR spec > > and > > > >> try > > > >> >> to > > > >> >> > understand how it deals with resources (I assumed sling > resource > > is > > > >> >> > directly based on JCR node concept). And got a good > understanding > > > of > > > >> how > > > >> >> > JCR thinks on resource and how they deal with it. > > > >> >> > > > > >> >> > Because we need to think of the mapping between the sling > wrapper > > > >> >> interface > > > >> >> > for resources which is org.apache.sling.api.resource.Resource > > > >> (which is > > > >> >> a > > > >> >> > JCR Node as I understand) and the Cassendra data layer. For > > > instance > > > >> >> > Cassandra provider will return a sling resource and it should > be > > > >> enrich > > > >> >> > with the properties/attributes which helps the sling resource > to > > > >> keep its > > > >> >> > state like resource meta data, resource type (which should be > the > > > JCR > > > >> >> node > > > >> >> > type), and etc. > > > >> >> > > > > >> >> > And the provider should only return a resource which only has > > such > > > >> very > > > >> >> > basic meta data. For instance, like > > > >> >> org.apache.sling.api.resource.Resource > > > >> >> > #getChild() #getChildren() we should not keep those in memory. > We > > > >> should > > > >> >> > return them on the fly from Cassandra. > > > >> >> > > > > >> >> > I think we should write a separate Sling Cassandra Adapter > layer > > > and > > > >> >> > provider should talk to Cassandra through Cassandra Adapter. I > > hope > > > >> this > > > >> >> > will make it more cleaner. > > > >> >> > Appreciate your valuable feedback. So that based on feedback I > > can > > > >> >> provide > > > >> >> > a patch which will reflect the basic architecture and keep on > > > >> patching > > > >> >> with > > > >> >> > future additions. > > > >> >> > > > > >> >> > > > > >> >> > On Fri, Mar 29, 2013 at 3:48 AM, Ian Boston <[email protected]> > > wrote: > > > >> >> > > > > >> >> >> Hi and welcome, > > > >> >> >> Some comments inline below. > > > >> >> >> > > > >> >> >> On 29 March 2013 06:02, Dishara Wijewardana < > > > >> [email protected]> > > > >> >> >> wrote: > > > >> >> >> > Hi all, > > > >> >> >> > I am Dishara Wijewardana, a student who is willing to take > > part > > > in > > > >> >> this > > > >> >> >> > GSoC 2013 . > > > >> >> >> > > > > >> >> >> > I have successfully completed GSoC 2012 in Apache Velocity > and > > > >> there I > > > >> >> >> have > > > >> >> >> > implemented JSR 223 support for Velocity. I found myself > > really > > > >> >> >> interested > > > >> >> >> > in this project since it covers very useful and interesting > > > >> topics. So > > > >> >> >> > thought of getting in to this project idea and provide a > good > > > >> proposal > > > >> >> >> for > > > >> >> >> > this project. > > > >> >> >> > > > > >> >> >> > So I did some research around sling which might be useful > for > > me > > > >> to > > > >> >> get > > > >> >> >> in > > > >> >> >> > to this project. I like sling as it sticks to community > > > standards > > > >> >> where > > > >> >> >> it > > > >> >> >> > uses a standard JCR2 repository to store resources which is > a > > > >> really > > > >> >> good > > > >> >> >> > thing to have. > > > >> >> >> > > > > >> >> >> > I went through the information provided in the JIRA[1] and > > > >> according > > > >> >> to > > > >> >> >> > that at the end of this project what is expected to have > > > >> implemented > > > >> >> is a > > > >> >> >> > ResourceProvider for Sling which tunnels with a Cassandra > > > >> (standalone > > > >> >> >> > one/cluster). > > > >> >> >> > > > >> >> >> yes, correct. > > > >> >> >> > > > >> >> >> > > > > >> >> >> > As far as I got to know, sling directly calls to Apache > > > JackRabbit > > > >> >> APIs > > > >> >> >> > (JCR APIs) to store resources. So I found a bit complicated > > this > > > >> >> project > > > >> >> >> > idea in that sense. Because if we are to implement a > Cassandra > > > >> backend > > > >> >> >> for > > > >> >> >> > Sling (as per this proposal), and Sling storage is on top of > > > >> >> JackRabbit, > > > >> >> >> > ideally what should happen is to make JackRabbit capable of > > > using > > > >> >> >> Cassandra > > > >> >> >> > as its resource persistent layer, and configure it through > > > Sling ? > > > >> >> Please > > > >> >> >> > correct me If I am wrong. > > > >> >> >> > > > >> >> >> Your right. > > > >> >> >> The idea is this, Sling resolves paths into Resources > > > >> >> >> ie /content/mywebsite/page1.html is resolved to a Resource > with > > a > > > >> path > > > >> >> >> of /content/mywebsite/page1 See [1]. Normally a JCR > > repository > > > >> >> >> takes ownership of everything under /, so all Resources are > JCR > > > >> >> >> Resources. > > > >> >> >> > > > >> >> >> However, with a ResourceProvider its possible to "mount" a > > > >> alternative > > > >> >> >> source of Resources at any location in the tree. eg: > > > >> >> >> If I create a ResourceProvider and configure it to respond to > > all > > > >> >> >> resource resolution operations at > > > >> >> >> /content/cassandra > > > >> >> >> > > > >> >> >> then > > > >> >> >> /content/cassandra/columnFamilyA/cassandraRowIDB > > > >> >> >> > > > >> >> >> will generate a Cassandra Resource instead of a JCR Resource. > > > >> >> >> > > > >> >> >> Initially the aim is to write a ResourceProvider that will > allow > > > >> >> >> Readonly access to a Cassandra cluster (cluster of one is ok > for > > > >> >> >> testing), but ultimately we would like to be able to write to > > that > > > >> >> >> cluster as well. > > > >> >> >> > > > >> >> >> Why Do it ? > > > >> >> >> Every storage platform has different characteristics, some are > > > ideal > > > >> >> >> for extreem volume writes of throw away data, some are ideal > for > > > >> >> >> extreem volume reads of precious audited transactrional data. > > > Being > > > >> >> >> able to "mount" multiple stores in Sling enables Sling to > > > integrate > > > >> >> >> data from all types of sources using best of breed address > each > > > use > > > >> >> >> case. (Thats the theory, anyway :)) > > > >> >> >> > > > >> >> > > > > >> >> > +1 and this is a wonderful architecture interms of > extensibility. > > > >> >> Something > > > >> >> > even a repository vendor like Jackrabbit also would want to > > follow. > > > >> >> Because > > > >> >> > they only have a JCR interfaced tree. > > > >> >> > > > > >> >> > > > > >> >> >> > > > >> >> >> I hope that makes things clearer. > > > >> >> >> > > > >> >> >> 1 http://sling.apache.org/site/resources.html > > > >> >> >> > > > >> >> >> > > > > >> >> >> > But if it is only to READ resources, this project is > > relatively > > > >> less > > > >> >> >> > complex (not quite sure though ;-) ) since what is required > is > > > to > > > >> >> have a > > > >> >> >> > JCR/Sling Resource compatible wrapper layer interface on top > > of > > > >> >> Cassendra > > > >> >> >> > to read cassandra data. > > > >> >> >> > > > >> >> >> Initially, just read. Then read with access control. The > > > read/write > > > >> >> >> with access control. > > > >> >> >> > > > >> >> > > > > >> >> > Read/Write complexity will be more or less the same as I feel. > > But > > > >> read > > > >> >> > write with access control is something we have to discuss > > > separately. > > > >> >> > Does sling maintaining access control directly with > jackrabbit's > > > >> >> > javax.jcr.security module ? Or any inhouse access control > layer ? > > > >> >> > > > > >> >> > > > > >> >> > > > > >> >> >> > > > >> >> >> > > > > >> >> >> > Appreciate any feedback and guidance on how to proceed. > > > >> >> >> > > > >> >> >> If you havent already you need to checkout the information at: > > > >> >> >> * http://www.google-melange.com/gsoc/homepage/google/gsoc2013 > > > >> >> >> * http://community.apache.org/gsoc.html > > > >> >> >> > > > >> >> >> especially the timeline and dates. > > > >> >> >> > > > >> >> >> There is no guarantee that Apache will be a GSoC organisation > > > >> >> >> (although its highly likely), and there are currently 129 > > project > > > >> >> >> proposals so there is no guarantee that you will get accepted > > as a > > > >> >> >> Student on this project, but the quality of your submission > and > > > your > > > >> >> >> enthusiasm will go a long way to making that happen. > > > >> >> >> > > > >> >> >> Good luck and I look forward to seeing you on these lists over > > the > > > >> >> >> summer. If you do make it through, I and everyone in this > > > community > > > >> >> >> will try and make it fun and rewarding for you. > > > >> >> >> > > > >> >> >> Best Regards > > > >> >> >> Ian > > > >> >> >> > > > >> >> >> > > > >> >> >> > > > >> >> >> > > > > >> >> >> > [1] - https://issues.apache.org/jira/browse/SLING-2798 > > > >> >> >> > > > > >> >> >> > -- > > > >> >> >> > Thanks > > > >> >> >> > /Dishara > > > >> >> >> > > > >> >> > > > > >> >> > > > > >> >> > > > > >> >> > -- > > > >> >> > Thanks > > > >> >> > /Dishara > > > >> >> > > > >> > > > > >> > > > > >> > > > > >> > -- > > > >> > Thanks > > > >> > /Dishara > > > >> > > > > > > > > > > > > > > > > -- > > > > Thanks > > > > /Dishara > > > > > > > > > > > > > > > > -- > > > Thanks > > > /Dishara > > > > > > > > > -- > Thanks > /Dishara >
