Hi Danny, How are Databases in the d-group accessed from the e-nodes in the e-group? Is it sufficient that both groups are defined in the same cluster? Databases are configured outside the Group configuration. Is a d-group created by only assinging hosts connected to a forest, and assigning all other hosts to the e-group which contains the needed app servers?
It would be helpful if you could give a more explict example. Is that possible without writing a lenghty email? Kind regards, Geert > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of > Danny Sokolsky > Sent: dinsdag 24 maart 2009 17:52 > To: General Mark Logic Developer Discussion > Subject: RE: [MarkLogic Dev General] Difference between eNode > and Data Node > > Hi Saptarshi, > > > > There is no requirement that an e-node must also have a > forest attached to it. In fact, in large implementations, > the norm is to configure e-nodes to do only e-node work and > d-nodes to do only d-node work. That is what Groups are for. > You might, for example, set up 2 groups, one for e-nodes and > one for d-nodes. The d-node groups do not need to have any > app servers on them, and the e-node groups do not need any > databases or forests. This means that each node can devote > its entire life (and all of its resources) to its role. For > example, if you have a group that only has d-nodes, you do > not need to allocate much expanded tree cache (that is used > for e-node processing). Similarly, if a group is only > e-nodes, they do not need to allocate much list cache or > compressed tree cache. Be extra careful when changing these > values, however, and make sure you know what role your hosts > are playing. > > > > Hosts in a MarkLogic Server cluster communicate via the xdqp > protocol, which is an internal communication mechanism. Any > changes to the cluster are communicated to the other hosts > via xdqp, and forest data is transferred to the e-node via > xdqp. All of this communication happens automatically. > > > > Hope that helps, > > -Danny > > > > From: [email protected] > [mailto:[email protected]] On Behalf Of > Saptarshi Newyork > Sent: Monday, March 23, 2009 10:08 PM > To: General Mark Logic Developer Discussion > Subject: RE: [MarkLogic Dev General] Difference between eNode > and Data Node > > > > Hi All, > > Thanks for a great description and examples. I still have > couple of questions to add: > > > > 1) I understand that same node can work as both eNode and > dNode, bu if I want to have separate eNode and dNode, in that > case, is there any difference in configuration of the host > for these two nodes? > > > > 2) In an architecture where both eNode and dNode exist, > suppose a request comes to eNode which requires an access to > forest. Then it's written that eNode will send the request to > dNode to access the forest. But every evaluator node(eNode) > is also attached to some forests. How this transfer of > request is achieved? How eNode can make a call to dNode? Is > there any configuration or coding required to achieve this? > Can under any scenario eNode access its own forest? > > > > Thanks in advance. > > regards, > > Saptarshi > > --- On Mon, 3/23/09, Danny Sokolsky <[email protected]> wrote: > > > From: Danny Sokolsky <[email protected]> > Subject: RE: [MarkLogic Dev General] Difference between > eNode and Data Node > To: "General Mark Logic Developer Discussion" > <[email protected]> > Date: Monday, March 23, 2009, 4:18 PM > > Hi Geert, > > Thanks for the great description. I will just add one > thing to what you > said: > > Whether a host acts as an e-node or a d-node depends on > what it is doing > at the time, and a given host in a MarkLogic cluster > can behave as an > e-node, a d-node, or both. For example, if you have a > single host > instance of MarkLogic Server, that host acts as both > the e-node (to > evaluate XQuery) and as the d-node (to perform forest > operations on > content). > > -Danny > > -----Original Message----- > From: [email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=general-bounces@ > developer.marklogic.com> > [mailto:[email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=general-bounces@ > developer.marklogic.com> ] On Behalf Of Geert > Josten > Sent: Monday, March 23, 2009 12:59 PM > To: General Mark Logic Developer Discussion > Subject: RE: [MarkLogic Dev General] Difference between > eNode and Data > Node > > Saptarshi, > > I am not an authority on this matter either, but I will > try to explain > as well as possible.. > > 1) MarkLogic Server is designed to operate with > evaluator nodes and > database nodes. The database nodes access content > stored in forests and > perform search queries over the forests. The evaluator nodes are > responsible for executing the Xquery code, webdav > requests, XDBC calls > etc. If the involved code to be executed doesn't access > any content > stored in the database (no cts:search calls, no doc > statements, etc), > but purely relies on in memory constructed content, > then database nodes > are not accessed. It has nothing to do with caching of > any kind, it is > just that content can be constructed on the fly, by > just incorporating > it in the Xquery script for instance. The example Eric > supplied is > valid. > > 2) MarkLogic Server does not handle failover when > filesystems crash. The > documentation > > (http://developer.marklogic.com/pubs/4.0/books/cluster.pdf) explains > that filesystem crashes should be handled by using a clustered > filesystem. There are some suggestions in that > document, but I can > imagine that a RAID configuration might suffice for > simples situations > as well. Forest-level failover works as follows: you > assign multiple > hosts to one physically shared forest. These hosts are > listed in order. > If the 1st host drops out, the 2nd host takes that forest over. > Replication of data is not necessary that way, making > it more efficient > and much more scalable. At the front-end you have also > the HTTP servers > etc on the hosts. You can have as many as you like. By putting a > hardware or software load-balancer in front you can > distribute calls > coming in at a single port to all available 'evaluator' nodes. > Load-balancing is not handled by MarkLogic Server > itself, there are > plenty solutions readily available so why bother. ;-) > > I am not sure whether an HTTP server is the actual > evaluator node, but I > don't think so. There is this Task Server configuration > page within the > MarkLogic Server Group Administration. This configures > Task threads on > all hosts within a single group. I have the impression > these act as > evaluator nodes and the Databases in the MarkLogic > Server Administration > correspond to the database nodes. Forest-level failover > is configured at > the Forest configuration pages. > > I hope this makes things clearer to you! > > Kind regards, > Geert > > > > > > Drs. G.P.H. Josten > Consultant > > > http://www.daidalos.nl/ > Daidalos BV > Source of Innovation > Hoekeindsehof 1-4 > 2665 JZ Bleiswijk > Tel.: +31 (0) 10 850 1200 > Fax: +31 (0) 10 850 1199 > http://www.daidalos.nl/ > KvK 27164984 > De informatie - verzonden in of met dit emailbericht - > is afkomstig van > Daidalos BV en is uitsluitend bestemd voor de > geadresseerde. Indien u > dit bericht onbedoeld hebt ontvangen, verzoeken wij u het te > verwijderen. Aan dit bericht kunnen geen rechten worden > ontleend. > > > > From: [email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=general-bounces@ > developer.marklogic.com> > > [mailto:[email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=general-bounces@ > developer.marklogic.com> ] On Behalf Of > > Saptarshi Newyork > > Sent: maandag 23 maart 2009 12:30 > > To: [email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=gene...@develope > r.marklogic.com> > > Subject: [MarkLogic Dev General] Difference between eNode and > > Data Node > > > > Hi , > > I have a few questions: > > > > 1) What is the difference between eNode and dNode? I have > > read that E-nodes are required to evaluate XQuery programs, > > XCC/XDBC requests, WebDAV requests, and other server > > requests.and dNodes are those which directly talks with the > > database/forest. It is also told that if the request does not > > need any forest data to complete, then an e-node request is > > evaluated entirely on the e-node. I do not understand how > > this is possible!! If eNode is meant for XQuery evaluation > > and XQuery needs an XML to process, then every eNode request > > should talk to dNode. Is there any caching mechanism? It will > > be great if anybody can explain this to me? > > > > > > > > 2) There are two failover mechanism explained in the > > documentation. Forest level failover and eNode level > > failover. It seems that forest data level failover is not > > handled by Marklogic. Like if the filesystem crashes, is > > there anyway by which Marklogic server replicates the forest > > to other hosts in same or different cluster? If this feature > > is not presently supported, then when can we expect this on > > the roadmap? > > > > > > > > Thanks in advance. > > > > > > > > regards, > > > > Saptarshi > > > > > > _______________________________________________ > General mailing list > [email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=gene...@develope > r.marklogic.com> > http://xqzone.com/mailman/listinfo/general > _______________________________________________ > General mailing list > [email protected] > <http://us.mc588.mail.yahoo.com/mc/compose?to=gene...@develope > r.marklogic.com> > http://xqzone.com/mailman/listinfo/general > > > > _______________________________________________ General mailing list [email protected] http://xqzone.com/mailman/listinfo/general
