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---+ Replication Example: Chain Topology

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---++ Introduction

The following How-To walks you through setting up Virtuoso RDF Graph Replication in a Chain Topology.
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---++Prerequisites

---+++Database INI Parameters

Suppose there are 3 Virtuoso instances respectively with the following ini parameters values:

   1. virtuoso1.ini:
<verbatim>
...
[Database]
DatabaseFile    = virtuoso1.db
TransactionFile = virtuoso1.trx
ErrorLogFile     = virtuoso1.log
...
[Parameters]
ServerPort               = 1111
SchedulerInterval        = 1
...
[HTTPServer]
ServerPort                  = 8891
...
[URIQA]
DefaultHost = localhost:8891
...
[Replication]
ServerName   = db1
...
</verbatim>
   1. virtuoso2.ini:
<verbatim>
...
[Database]
DatabaseFile    = virtuoso2.db
TransactionFile = virtuoso2.trx
ErrorLogFile     = virtuoso2.log
...
[Parameters]
ServerPort               = 1112
SchedulerInterval        = 1
...
[HTTPServer]
ServerPort                  = 8892
...
[URIQA]
DefaultHost = localhost:8892
...
[Replication]
ServerName   = db2
...
</verbatim>
   1. virtuoso3.ini:
<verbatim>
...
[Database]
DatabaseFile    = virtuoso3.db
TransactionFile = virtuoso3.trx
ErrorLogFile     = virtuoso3.log
...
[Parameters]
ServerPort               = 1113
SchedulerInterval        = 1
...
[HTTPServer]
ServerPort                  = 8893
...
[URIQA]
DefaultHost = localhost:8893
...
[Replication]
ServerName   = db3
...
</verbatim>
 

---+++Database DSNs

Use the ODBC Administrator on your Virtuoso host (e.g., on Windows, *Start* menu -> *Control Panel* -> *Administrative Tools* -> <b>Data Sources (ODBC)</b>; on Mac OS X, <code><nowiki>/Applications/Utilities/OpenLink ODBC Administrator.app</nowiki></code>) to create a System DSN for each of db1, db2, db3, with names db1, db2 and db3, respectively.

---+++Install Conductor package

On each of the 3 Virtuoso instances install the [[https://virtuoso.openlinksw.com/download/][conductor_dav.vad]] package.

---++Create Publication on db1

   1. Go to http://localhost:8891/conductor and log in as dba
   1. Go to Conductor -> Replication -> Transactional -> Publications
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   1. Click <b>Enable RDF Publishing</b>
   1 As result publication with the name <b>RDF Publication</b> should be created
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   1 Click the link which is the publication name. 
   1 The publication items page will be shown:
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   1 Enter for Graph IRI:
<verbatim>
http://example.org
</verbatim>
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   1 Click Add New
   1 The item will be created and shown in the list of items for the currently viewed publication. 
%BR%%BR%<img src="%ATTACHURLPATH%/m5.png" />%BR%%BR%

---++Create subscription from db2 to db1's Publication

   1 Log in at http://localhost:8892/conductor.
   1 Go to Replication -> Transactional -> Subscriptions:
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   1 Click <b>New Subscription</b>:
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   1 From the list of "Specify new data source" select Data Source db1:
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   1 Enter for db1 dba user credentials:
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   1 Click "Add Data Source":
   1 As result <b>db1</b> will be shown in the "Connected Data Sources" list. 
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   1 Click "Publications list":
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   1 As result will be shown the list of available publications for the selected data source. Select the one with name "RDF Publication" and click "List Items".
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   1 As result will be shown the "Confirm subscription" page. 
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   1 The sync interval by default is 10 minutes. For the testing purposes, we will change it to 1 minute.
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   1 Click "Subscribe".
   1 The subscription will be created. 
%BR%%BR%<img src="%ATTACHURLPATH%/m15.png" />%BR%%BR%

---++Create Publication on db2

   1. Go to http://localhost:8892/conductor and log in as dba,
   1. Go to Conductor -> Replication -> Transactional -> Publications:
%BR%%BR%<img src="%ATTACHURLPATH%/m16.png" />%BR%%BR%
   1. Click <b>Enable RDF Publishing</b>:
   1 As result publication with the name <b>RDF Publication</b> should be created:
%BR%%BR%<img src="%ATTACHURLPATH%/m17.png" />%BR%%BR%
   1 Click the link which is the publication name. 
   1 The publication items page will be shown:
%BR%%BR%<img src="%ATTACHURLPATH%/m18.png" />%BR%%BR%
   1 Enter for Graph IRI:
<verbatim>
http://example.org
</verbatim>
%BR%%BR%<img src="%ATTACHURLPATH%/m19.png" />%BR%%BR%
   1 Click Add New.
   1 The item will be created and shown in the list of items for the currently viewed publication. 
%BR%%BR%<img src="%ATTACHURLPATH%/m20.png" />%BR%%BR%


---++Create subscription from db3 to db2's Publication

   1 Log in at http://localhost:8893/conductor.
   1 Go to Replication -> Transactional -> Subscriptions:
%BR%%BR%<img src="%ATTACHURLPATH%/m21.png" />%BR%%BR%
   1 Click <b>New Subscription</b>:
%BR%%BR%<img src="%ATTACHURLPATH%/m22.png" />%BR%%BR%
   1 From the list of "Specify new data source" select Data Source db2:
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   1 Enter for db2 dba user credentials:
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   1 Click "Add Data Source":
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   1 As result <b>db2</b> will be shown in the "Connected Data Sources" list. Select it and click "Publications list":
%BR%%BR%<img src="%ATTACHURLPATH%/m26.png" />%BR%%BR%
   1 As result will be shown the list of available publications for the selected data source. Select the one with name "RDF Publication" and click "List Items".
%BR%%BR%<img src="%ATTACHURLPATH%/m27.png" />%BR%%BR%
   1 As result will be shown the "Confirm subscription" page.  
%BR%%BR%<img src="%ATTACHURLPATH%/m28.png" />%BR%%BR%
   1 The sync interval by default is 10 minutes. For the testing purposes, we will change it to 1 minute.
%BR%%BR%<img src="%ATTACHURLPATH%/m29.png" />%BR%%BR%
   1 Click "Subscribe".
   1 The subscription will be created. 
%BR%%BR%<img src="%ATTACHURLPATH%/m30.png" />%BR%%BR%

---++Insert Data into a Named Graph on the db1 Virtuoso Instance

   1. Log in at http://localhost:8891/conductor.
   1 Go to Linked Data-> Quad Store Upload: 
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   1 In the shown form:
      1 Tick the box for <b>Resource URL</b> and enter your resource URL, e.g.:
<verbatim>
http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this
</verbatim>
      1 Enter for Named Graph IRI:
<verbatim>
http://example.org
</verbatim>
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   1 Click Upload.
   1 Should be shown message for successful upload:
%BR%%BR%<img src="%ATTACHURLPATH%/m33.png" />%BR%%BR%
   1 Check the count of the inserted triples by executing a query like the following against the SPARQL endpoint, 
http://localhost:8891/sparql:
<verbatim>
SELECT COUNT(*) 
   FROM <http://example.org>
WHERE { ?s ?p ?o }
</verbatim>
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   1 Should be shown <b>57</b> as total.
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---++Check data on the Destination instances db2 and db3

   1 To check the starting count, on each of the Destination Virtuoso Instances db2 and db3 from  SPARQL Endpoint execute:
<verbatim>
SELECT COUNT(*) 
   FROM <http://example.org>
WHERE { ?s ?p ?o }
</verbatim>
   1 Should return <b>57</b> as total.
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---++Add new data on db1

   1 Disconnect db2 and db3.
   1 On the Host Virtuoso Instance db1 go to Conductor -> Database -> Interactive SQL enter the following statement:
<verbatim>
SPARQL INSERT INTO GRAPH <http://example.org> 
  { 
     <http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this>
     <http://xmlns.com/foaf/0.1/interest>
     <http://dbpedia.org/resource/Web_Services> 
  } ;
SPARQL INSERT INTO GRAPH <http://example.org> 
  { 
    <http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this>  	
    <http://xmlns.com/foaf/0.1/interest>  	
    <http://dbpedia.org/resource/Web_Clients> 
  } ;
SPARQL INSERT INTO GRAPH <http://example.org> 
  { 
    <http://www.openlinksw.com/dataspace/person/kidehen@openlinksw.com#this>  	
    <http://xmlns.com/foaf/0.1/interest>  	
    <http://dbpedia.org/resource/SPARQL> 
  } ;
</verbatim>
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   1 Click "Execute".
   1 As result the triples will be inserted:
%BR%%BR%<img src="%ATTACHURLPATH%/m36a.png" />%BR%%BR%
   1 Check the count of the destination instance graph's triples by executing the following query like against the SPARQL endpoint, 
http://localhost:8891/sparql:
<verbatim>
SELECT COUNT(*) 
   FROM <http://example.org>
WHERE { ?s ?p ?o }
</verbatim>
   1 Should be shown <b>60</b> as total.
%BR%%BR%<img src="%ATTACHURLPATH%/m38.png" />%BR%%BR%

---++Check again data on the Destination instances db2 and db3
 
   1 Start instances db2 and db3.
   1 To confirm that the triple count has increased by the number of inserted triples, execute the following on the Destination Virtuoso Instance db2 and db3 SPARQL Endpoint:
<verbatim>
SELECT COUNT(*) 
   FROM <http://example.org>
WHERE { ?s ?p ?o }
</verbatim>
   1 Should be shown <b>60</b> as total:
%BR%%BR%<img src="%ATTACHURLPATH%/m38.png" />%BR%%BR%

---++Related

   * [[VirtGraphReplicationStar][Replication Example: Star Topology]]
   * [[VirtGraphReplicationBiDirectional][Replication Example: 2-node Bi-directional Topology]]   
   * [[VirtGraphReplicationPSQL][Set up RDF Replication via procedure calls]]   
   * [[http://ods.openlinksw.com/wiki/ODS/VirtPubSubHub][Example of Linked Data Usage of PubSubHubbub Implementation]]
   * [[VirtRdfReplScenarios][Exploit Virtuoso's Replication Functionality Web based Solutions]]