Re: [Neo4j] Multiple users on a embedded graphdb
No problem at all. As tx are bound to the executing thread. And the singleton graph-db instance is the way to go. Good Luck with your efforts Michael Am 11.05.2011 um 17:04 schrieb John Doran: > Thanks Micheal, > Good points, I have 3 weeks to finish up(along with a mountain of other > things to do so I can't see the server as and option, I'm really looking for > a quick work around because of time limitations. I actually helped Rene get > stated with combining the two, I have the two working well together. Apart > from the problem I have now of distributions. Could a workaround be to have > a singleton instance of the db when clients are performing queries run from > this instance, or would there be transactional problems? > Regards, John. > ___ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
Re: [Neo4j] Multiple users on a embedded graphdb
Thanks Micheal, Good points, I have 3 weeks to finish up(along with a mountain of other things to do so I can't see the server as and option, I'm really looking for a quick work around because of time limitations. I actually helped Rene get stated with combining the two, I have the two working well together. Apart from the problem I have now of distributions. Could a workaround be to have a singleton instance of the db when clients are performing queries run from this instance, or would there be transactional problems? Regards, John. ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
Re: [Neo4j] Multiple users on a embedded graphdb
John,
as the exception says and Marko said before you can only have one embedded
graph db instance.
Accessing the db from the outside needs a protocol that allows the client to
talk to the db.
Either you go with the Neo4j-Server and use the provided graph-algorithms or
write your own Server Plugin that does that. Then your GWT clients can access
that remotely.
But it is perhaps more sensible to rely on GWT's remoting protocol and just
expose a Service in the Server that allows clients to call the graph algo
methods. The Service should then instantiated (guice?) as a singleton keeping
the single graph db.
There is a recent screencast by René Pickhardt on how to integrate neo4j and gwt
http://www.rene-pickhardt.de/how-to-combine-neo4j-with-gwt-and-eclipse
Perhaps this helps you to solve your problems.
P.S. Even with custom thread handling you should create the Graph-Database
upfront and pass it by reference to the threads which can then access it
concurrently. For remote clients you would do ServerSocket.listen and ~.accept
and spawn (or re-use and even better a ThreadPool) a new thread for handling
the client request. But writing your own socket layer is definitively overkill.
Cheers
Michael
Am 11.05.2011 um 15:36 schrieb John Doran:
> Hi all,
> Thanks for the help with the multiple user on the embedded problem, I'm
> still getting the exception(I am a little rusty at working with threads). So
> I run the tread when wanting to work with the db and then in a do/while
> statement check if complete(if so yield). But when a second user tries to
> access from another browser/computer I get the dreaded exception(see below).
> Any suggestions/workarounds would be great! Or an example of where people
> have used threads in interacting with neo4j.
> Regards,
> John.
>
> RPC server side code:
> processAStar = new ProcessAStarAlgorithm(latitude1, longitude1, latitude2,
> longitude2, desiredDistance);
> boolean processing = true;
> Thread runner = new Thread(){
> public void run(){
> processAStar.configureSearch();//create the graph db and process
> calculations
> System.out.println("Running thread");
> }
> };
> runner.start();
> do {
> try {
> Thread.sleep(1000);
> System.out.println("Sleeping thread");
> if(processAStar.calculationComplete==true){
> System.out.println("Calculation complete in thread");
> sp = processAStar.getShortestPathRepresentation();
> processing = false;
> Thread.yield();
> }
> } catch (InterruptedException exc) {
> }
> } while (processing);
> return sp;
>
> Exception:
> Exception in thread "Thread-21"
> org.neo4j.graphdb.TransactionFailureException: Could not create data source
> [nioneodb], see nested exception for cause of error
> at
> org.neo4j.kernel.impl.transaction.TxModule.registerDataSource(TxModule.java:154)
> at org.neo4j.kernel.GraphDbInstance.start(GraphDbInstance.java:107)
> at org.neo4j.kernel.EmbeddedGraphDbImpl.(EmbeddedGraphDbImpl.java:168)
> at
> org.neo4j.kernel.EmbeddedGraphDatabase.(EmbeddedGraphDatabase.java:81)
> at
> org.neo4j.kernel.EmbeddedGraphDatabase.(EmbeddedGraphDatabase.java:65)
> at
> com.routeplanner.fyp.pathfinder.ProcessAStarAlgorithm.getWaypointsClose(ProcessAStarAlgorithm.java:72)
> at
> com.routeplanner.fyp.pathfinder.ProcessAStarAlgorithm.configureSearch(ProcessAStarAlgorithm.java:307)
> at
> com.routeplanner.fyp.server.PlanRouteServiceImpl$1.run(PlanRouteServiceImpl.java:22)
> Caused by: java.lang.reflect.InvocationTargetException
> at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
> at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
> at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
> at java.lang.reflect.Constructor.newInstance(Unknown Source)
> at
> org.neo4j.kernel.impl.transaction.XaDataSourceManager.create(XaDataSourceManager.java:74)
> at
> org.neo4j.kernel.impl.transaction.TxModule.registerDataSource(TxModule.java:148)
> ... 7 more
> Caused by: java.lang.IllegalStateException: Unable to lock store
> [C:\fyp_2.011\neo4j-db\neostore], this is usually caused by another Neo4j
> kernel already running in this JVM for this particular store
> at
> org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.checkStorage(CommonAbstractStore.java:266)
> at
> org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.(CommonAbstractStore.java:163)
> at
> org.neo4j.kernel.impl.nioneo.store.AbstractStore.(AbstractStore.java:120)
> at org.neo4j.kernel.impl.nioneo.store.NeoStore.(NeoStore.java:64)
> at
> org.neo4j.kernel.impl.nioneo.xa.NeoStoreXaDataSource.(NeoStoreXaDataSource.java:128)
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Re: [Neo4j] Multiple users on a embedded graphdb
Hi all,
Thanks for the help with the multiple user on the embedded problem, I'm
still getting the exception(I am a little rusty at working with threads). So
I run the tread when wanting to work with the db and then in a do/while
statement check if complete(if so yield). But when a second user tries to
access from another browser/computer I get the dreaded exception(see below).
Any suggestions/workarounds would be great! Or an example of where people
have used threads in interacting with neo4j.
Regards,
John.
RPC server side code:
processAStar = new ProcessAStarAlgorithm(latitude1, longitude1, latitude2,
longitude2, desiredDistance);
boolean processing = true;
Thread runner = new Thread(){
public void run(){
processAStar.configureSearch();//create the graph db and process
calculations
System.out.println("Running thread");
}
};
runner.start();
do {
try {
Thread.sleep(1000);
System.out.println("Sleeping thread");
if(processAStar.calculationComplete==true){
System.out.println("Calculation complete in thread");
sp = processAStar.getShortestPathRepresentation();
processing = false;
Thread.yield();
}
} catch (InterruptedException exc) {
}
} while (processing);
return sp;
Exception:
Exception in thread "Thread-21"
org.neo4j.graphdb.TransactionFailureException: Could not create data source
[nioneodb], see nested exception for cause of error
at
org.neo4j.kernel.impl.transaction.TxModule.registerDataSource(TxModule.java:154)
at org.neo4j.kernel.GraphDbInstance.start(GraphDbInstance.java:107)
at org.neo4j.kernel.EmbeddedGraphDbImpl.(EmbeddedGraphDbImpl.java:168)
at
org.neo4j.kernel.EmbeddedGraphDatabase.(EmbeddedGraphDatabase.java:81)
at
org.neo4j.kernel.EmbeddedGraphDatabase.(EmbeddedGraphDatabase.java:65)
at
com.routeplanner.fyp.pathfinder.ProcessAStarAlgorithm.getWaypointsClose(ProcessAStarAlgorithm.java:72)
at
com.routeplanner.fyp.pathfinder.ProcessAStarAlgorithm.configureSearch(ProcessAStarAlgorithm.java:307)
at
com.routeplanner.fyp.server.PlanRouteServiceImpl$1.run(PlanRouteServiceImpl.java:22)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at
org.neo4j.kernel.impl.transaction.XaDataSourceManager.create(XaDataSourceManager.java:74)
at
org.neo4j.kernel.impl.transaction.TxModule.registerDataSource(TxModule.java:148)
... 7 more
Caused by: java.lang.IllegalStateException: Unable to lock store
[C:\fyp_2.011\neo4j-db\neostore], this is usually caused by another Neo4j
kernel already running in this JVM for this particular store
at
org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.checkStorage(CommonAbstractStore.java:266)
at
org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.(CommonAbstractStore.java:163)
at
org.neo4j.kernel.impl.nioneo.store.AbstractStore.(AbstractStore.java:120)
at org.neo4j.kernel.impl.nioneo.store.NeoStore.(NeoStore.java:64)
at
org.neo4j.kernel.impl.nioneo.xa.NeoStoreXaDataSource.(NeoStoreXaDataSource.java:128)
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Re: [Neo4j] Multiple users on a embedded graphdb
hi john,
imho the gwt is just a webapp. so i'm a bit confused why talking about threads
in a j2ee env?
if i understand you right you want to share one neo4j instance between
different gwt apps(services). i would propose creating a context-listener, on
application startup the embedded-graph-db is placed in the servlet context.
(see the code-snippets)
a other approach would be accessing the neo4j-server direct from the gwt
(javascript) code through the rest-api. this assumes a driver written in
gwt-java/javascript.
@jim i hope to find the time this friday creating a lab-project this friday for
this :)
cheers
/thomas
// register in web.xml
public class NeoContextListner implements ServletContextListener {
private static final String CONTEXT_KEY = "neo4j-instance";
public static EmbeddedGraphDatabase getNeo4JInstance(ServletContext
servletContext) {
return (EmbeddedGraphDatabase) servletContext.getAttribute(CONTEXT_KEY);
}
public void contextInitialized(ServletContextEvent servletContextEvent) {
EmbeddedGraphDatabase db = new EmbeddedGraphDatabase("/tmp/db");
ServletContext servletContext = servletContextEvent.getServletContext();
servletContext.setAttribute(CONTEXT_KEY, db);
}
public void contextDestroyed(ServletContextEvent servletContextEvent) {
ServletContext servletContext = servletContextEvent.getServletContext();
EmbeddedGraphDatabase db = getNeo4JInstance(servletContext);
db.shutdown();
}
}
usage:
public class TestServiceImpl extends RemoteServiceServlet implements
TestService {
public AnyResult doIt(String argument) {
EmbeddedGraphDatabase db =
NeoContextListner.getNeo4JInstance(getServletContext());
use it
}
}
Am 09.05.2011 um 23:11 schrieb Christoph K.:
> Hi John,
>
> if i unterstand Jim right, he means that you should fire up threads on the
> serverside implementation which handle client requests and deal with a
> single instance of the embeddedgraphdatabase.
>
> greetings
> Chris
>
> On Mon, May 9, 2011 at 11:06 PM, John Doran wrote:
>
>> Hi Jim,
>> Thanks for the reply, I haven't delved into the server aspect of neo4j(I'll
>> leave that until I finish up college). I'll have to refresh my threading
>> knowledge, you reckon each time users want to interact with the db to
>> create
>> a thread and this would stop any exceptions relating to not being able to
>> connect to the database(because it's in use).
>> Regards,
>> John.
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Re: [Neo4j] Multiple users on a embedded graphdb
Hi John, if i unterstand Jim right, he means that you should fire up threads on the serverside implementation which handle client requests and deal with a single instance of the embeddedgraphdatabase. greetings Chris On Mon, May 9, 2011 at 11:06 PM, John Doran wrote: > Hi Jim, > Thanks for the reply, I haven't delved into the server aspect of neo4j(I'll > leave that until I finish up college). I'll have to refresh my threading > knowledge, you reckon each time users want to interact with the db to > create > a thread and this would stop any exceptions relating to not being able to > connect to the database(because it's in use). > Regards, > John. > ___ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
Re: [Neo4j] Multiple users on a embedded graphdb
Hey,
You can have multiple threads talking to the same DB reference. You can not
create multiple graph database services over the same directory. Thus,
final graph = new GraphDatabaseService('/tmp/test')
for(int i=0;i<10;i++) {
new Thread {
public void run() {
// do something to graph
}
}.start()
}
But not:
graph = new GraphDatabaseSerice('/tmp/test');
graph = new GraphDatabaseService('/tmp/test');
Hope that helps,
Marko.
http://markorodriguez.com
On May 9, 2011, at 3:06 PM, John Doran wrote:
> Hi Jim,
> Thanks for the reply, I haven't delved into the server aspect of neo4j(I'll
> leave that until I finish up college). I'll have to refresh my threading
> knowledge, you reckon each time users want to interact with the db to create
> a thread and this would stop any exceptions relating to not being able to
> connect to the database(because it's in use).
> Regards,
> John.
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Re: [Neo4j] Multiple users on a embedded graphdb
Hi Jim, Thanks for the reply, I haven't delved into the server aspect of neo4j(I'll leave that until I finish up college). I'll have to refresh my threading knowledge, you reckon each time users want to interact with the db to create a thread and this would stop any exceptions relating to not being able to connect to the database(because it's in use). Regards, John. ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
Re: [Neo4j] Multiple users on a embedded graphdb
Hi John, I think threads are your friend. Or you could use our REST API (depending on your requirements) where threads are our friends inside the Neo4j server. Jim ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
[Neo4j] Multiple users on a embedded graphdb
Hi all, Have been using my project in test mode(by myself) and have just came up with a problem. My app through GWT is client server, so if a second client wants to calculate a shortest path(using the embedded graphdb) they cannot connect to my db because its in use by another client, any suggestions? I was thinking some kind of threading solution? Regards, John. ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
