It is required to run multiple application on same neo4j db. But when I try to do that, I am meeting a problem about locking.
Neo4j is locking itself when an application is using it. Multiple application can't be run.
The exception is like,
Unable to lock store [/opt/neo4j-lojika-db/neostore.relationshiptypestore.db.names], this is usually a result of some other Neo4j kernel running using the same store
Is there a way to run multiple web application with same embedded neo4j db.
Thank you!
You can't do this way. You have two options
Use Neo4j HA or
Run Neo4j in server mode rather than embedded mode. If your application is simple then you can use the REST api provided by Neo4j out of box. If your service layer is more involved then, put a service layer on top of a single Neo4j embedded instance and let each application talk to Neo4j through this service layer.
Related
I'm new to Neo4j and am learning the Desktop application. I see that I can Add a Database (I can either Create a Local Graph or Connect to a Remote Graph). Creating a local graph obviously means creating a database on my computer, one with it's own bolt://... URL ID of some sort. If instead I Add a Remote Graph, does this imply that I can connect to another local graph stored on my laptop for example if I know its bolt id? I presume I can't but I want to make sure.
Next, if Remote implies stored in the cloud or served somehow, short of setting up a Neo4j instance on AWS or via another 3rd party does Neo4j come with its own easy way to setup a "remote" instance and where would this live? Does Neo have it's own cloud?
Remote Graph implies that there's a running Neo4j instance out there "somewhere" that we can connect to via the bolt URL, similar to how we would connect from a client application using a Neo4j driver (after all, Neo4j Desktop and Neo4j Browser are both client applications and connect via Neo4j drivers).
That might be a server instance somewhere set up by your company, or an instance running from your own laptop (not launched from Desktop), or maybe a Neo4j Aura instance you've set up yourself, or something on AWS or another cloud.
You can't administer remote instances, as bolt connections do not allow for starting/stopping Neo4j or other operations that require command-line access (though 4.0 security administration via the system db is supported).
For the most part though Desktop is agnostic of where or how the remote instance is set up, it just requires a bolt URL that can be used to connect to the instance or cluster.
I am planning to create a desktop app (Java or C# WPF) which would be used by multiple users. The requirements are such that a Graph DB like Neo4j fits perfectly into the scheme of things. I have done some investigations and it looks really good. I am working on the community edition. Now here is the problem. From what I have observed, I am able to make only one connection to the database. The moment I try to make a connection from another instance I get an error. Even accessing on localhost:7474 gives an error.
Is this by design? I understand that in a web App, I can still use a static reference to a single DB instance and work with it. But in a desktop app scenario how do I ensure that multiple users are able to access the database from their apps?
Your app instances can access the same neo4j server through its REST API. There is no need to directly connect to the DB.
Here is a page that shows you how to do that in Java.
I am developing a social networking website with Grails and MYSQL DB. But I am planning to move to Neo4j DB. Grails supports complete GORM features with MYSQL. But I am sure about the same features in Neo4j. There is a Grails plugin for Neo4j which does not support some of the features that is required to support big websites. So I am planning to use the native Neo4j API. From Grails how to connect to Neo4j DB? There are two scenarios in my case.
Case 1:
Neo4j server is up and running. How to connect and perform the database transactions?
Case 2:
Neo4j server is not running. How to connect and perform the database transactions? I was able to connect using GraphDatabaseService class. But why would one need to connect to DB which is not running. What is this class GraphDatabaseService particularly used for?
I want to use the native Neo4j API to get access to maximum features. Is there a better approach to build the application.
The Grails Neo4j GORM plugin in version 2.0.0.M01 is able to run embedded mode only - so the JVM running the Grails applications spawns the database inside the same JVM. Next milestone (M02) will add support for accessing Neo4j via REST.
In case you don't want to transparently use the GORM methods to talk to Neo4j you can always use direct access by emitting Cypher statements or accessing GraphDatabaseService directly (only on embedded mode of course).
I'm working on an application using Spring Data Neo4j that works with an embedded Neo4j Server. I would like for my application to be able to work with a cluster containing 3 Neo4j nodes, one of this nodes being the embedded server.
I am trying to accomplish some sort of load balancing within the cluster: 1. round-robin requests on each server or 2. write requests on the master embedded server and read requests on the other two servers.
Does Spring Data Neo4j have any kind of load balancing mechanism out of the box? What configuration is necessary to achieve this? Do I need additional tools like HAProxy or mod_proxy? Is there any example of how they can be integrated with the Neo4j cluster and Spring Data Neo4j?
A load balancer component is not part of Neo4j nor part of Spring Data Neo4j. For a sample setup using Neo4j as server is documented at http://docs.neo4j.org/chunked/stable/ha-haproxy.html.
Since your application uses SDN in embedded HA mode, you need to expose the status of your local instance (master or slave) yourself to achieve the same like /db/manage/server/ha/master does in server mode. You might use HighlyAvailableGraphDatabase.isMaster() in your implementation.
I have installed neo4j version 1.9.5 and tried some java sample to access / write data into graphdb, but for every action the existing graph db instance is created newly using below,
graphDb = new GraphDatabaseFactory().newEmbeddedDatabase("c:/movies/moviesdb"); so is it possible to access and execute cypher query through java on active Neo4j db without REST API concept.
Note : Consider Ne04j DB is already started and running
When running Neo4j as a server process, you communicate with your DB only via REST. The other usage model is embedded. Here you're application code controls the lifecycle of the DB by using new GraphDatabaseFactory().newEmbeddedDatabase(). These two modes are distinct.