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 <i...@tfd.co.uk> 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 <ddwijeward...@gmail.com> > 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 < > > ddwijeward...@gmail.com > > > wrote: > > > > > Hi Ian, > > > > > > On Tue, Apr 2, 2013 at 4:44 AM, Ian Boston <i...@tfd.co.uk> wrote: > > > > > >> On 2 April 2013 07:55, Dishara Wijewardana <ddwijeward...@gmail.com> > > >> 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 <i...@tfd.co.uk> 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 < > ddwijeward...@gmail.com > > > > > >> >> 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 <i...@tfd.co.uk> > wrote: > > >> >> > > > >> >> >> Hi and welcome, > > >> >> >> Some comments inline below. > > >> >> >> > > >> >> >> On 29 March 2013 06:02, Dishara Wijewardana < > > >> ddwijeward...@gmail.com> > > >> >> >> 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
