Hi Matt , I was looking for more details on the inner workings . I came across this https://markmail.org/message/jbkrsmz3krllqghr where it mentioned that changes in the cluster would eventually appear across other nodes and this is not a mongo specific issue but something oak has introduced . I can set the write concern to majority in mongo but if oak has its own eventually consistency model this can cause stale reads from other nodes which would be a problem with the distributed job Im trying to create.
Thanks On Fri, Dec 14, 2018 at 8:02 AM Matt Ryan <[email protected]> wrote: > Hi Emily, > > Content is stored in Oak in two different configurable storage services. > This is a bit of an oversimplification, but basically the structure of > content repository - the content tree, nodes, properties, etc. - is stored > in a Node Store [0] and the binary content is stored in a Blob Store [1] > (you'll also sometimes see the term "data store"). Oak manages all of this > transparently to external clients. > > Oak clustering is therefore achieved by configuring Oak instances to use > clusterable storage services underneath [2]. For the node store, an > implementation of a DocumentNodeStore [3] is needed; one such > implementation uses MongoDB [4]. For the blob store, an implementation of > a SharedDataStore is needed. For example, both the SharedS3DataStore and > AzureDataStore implementations can be used as a data store for an Oak > cluster. > > So, assume you were using MongoDB and S3. Setting up an Oak cluster then > merely means that you have more than one Oak instance, each of which is > configured to use the MongoDB cluster as the node store, and S3 as the data > store. > > > [0] - > > https://github.com/apache/jackrabbit-oak/blob/trunk/oak-doc/src/site/markdown/nodestore/overview.md > [1] - > > https://github.com/apache/jackrabbit-oak/blob/trunk/oak-doc/src/site/markdown/plugins/blobstore.md > [2] - > > https://github.com/apache/jackrabbit-oak/blob/trunk/oak-doc/src/site/markdown/clustering.md > [3] - > > https://github.com/apache/jackrabbit-oak/blob/trunk/oak-doc/src/site/markdown/nodestore/documentmk.md > [4] - > > https://github.com/apache/jackrabbit-oak/blob/trunk/oak-doc/src/site/markdown/nodestore/document/mongo-document-store.md > > > Does that help? > > > -MR > > On Thu, Dec 13, 2018 at 5:52 PM ems eril <[email protected]> wrote: > > > Hi Team , > > > > Im really interested in understanding how oak cluster works and how do > > cluster nodes sync up . These are some of the questions I have > > > > 1) How does the nodes sync > > 2) What is the mongo role > > 3) How does indexes in cluster work and sync up > > 4) What is the distributed model master/slave multi master > > 5) What is co-ordinated by the master node > > 6) How is master node elected > > > > One use case I have is to be able to leverage a oak cluster to be able > > to upload images/videos and have a consumer on one of the nodes process > it > > in a distributed way . I like to try my best to avoid unnecessary read > > checks if possible . > > > > Thanks > > > > Emily > > >
