Dears, we're experiencing some random issue with our Neo4J 4.2 Enterprise cluster and a bunch of Spring-based applications.
We're using SDN6 and reactive sessions to run custom queries on our cluster but sometimes we get this error
Message 'COMMIT' cannot be handled by a session in the READY state.
both on db side and on application.
We're currently using transactional functions to leverage on the retry logic as explained here
Any ideas?
Best,
FB
Related
I'm starting a new Spring boot project and I've chosen a neo4j graph database as there is a lot of connected data.
I would like to use Reactive Streams in the project as there is a lot of push notifications from the server to the client. I'm looking at using Spring Webflux for this reason.
I'm weary of accidentally using blocking calls/api's that will negate the decision to use webflux.
I've searched for information on using neo4j with reactive streams. It doesn't look like there is a reactive driver at the moment, although there is an asynchronous mechanism using CompletableFuture.
Please could I have some guidance on how to fit these two peices, webflux & neo4j, together.
thanks
I'm working on a webapp running on Tomcat which using spring-data to connect to a neo4j graph in embedded mode.
I would like to use neo4j server instead of the embedded mode and I am looking for some help to be sure about how to do that.
Some of my application services are quite difficult and combine, in a single transaction, the result of several cypher requests in a dto sent back to the user.
First I thought that I have to create a server unmanaged extension and I think I should follow these following steps.
- Keep my webapp with springMVC and spring security to hold and secure users sessions.
- Regroup all my transactional services in a specific jar my-app.jar
- Use Jax-RS to add a REST access point on each of my service of my-app.jar
- use something like spring restTemplate from my spring controller to call services from my-app.jar
First question : is this way of doing things is the good way ?
Second question : I have many spring injection in my services layer. How can I keep them working (how can I add dependencies in the server extension ?
Then I discovered graphAware and I wonder if I should use it instead.
And finally I just read this post http://jexp.de/blog/2014/12/spring-data-neo4j-improving-remoting-performance/ and it seems that I should use
the SpringCypherRestGraphDatabase (as explain in the bold text at the end of the article).
Well, I'm a little bit lost and I would appreciate any help to use neo4j server instead the embedded mode for my application which contain some complexe transactions.
You have a number of options here and you are on the right track with your thinking.
Option 1:
If your use cases are business-logic-heavy, and your question suggests that they are, going the unmanaged extension route is one option.
Essentially, you can then combine the most performant Java API and Cypher (if you wish) to perform your use case. I wouldn't use SDN here by the way, so you have to do your mapping manually, but is there really any mapping? Maybe you just want to execute traversals / Cypher queries for each one of your use cases.
Each use case then exposes a simple REST API, which is consumed by your Spring-powered application running Spring MVC, Spring Security, and all that. You can use the RestTemplate from Spring in your app's Controllers.
To add a twist to all that, you can use the GraphAware Framework to develop the "unmanaged extension" using Spring MVC as well. That would be my preferred option, knowing nothing about your domain/app.
Option 2:
Use the new version of SDN (v4) as Michael suggests. This allows you to run your application with annotated domain objects, Spring MVC, Security, et al. Operations (CRUD and other) are automatically translated to Cypher and sent across the wire to Neo4j running in server mode (no extensions needed). Results are then marshalled back to Java objects.
We're about to release Milestone 1 of SDN v4. It shouldn't take more than a week. That said, it is still going to be a Milestone release, thus not ready for production. A GA release is expected in May (ish).
You can already try SDN v4 yourself. Clone this repo: https://github.com/spring-projects/spring-data-neo4j, make sure you're on the 4.0 branch, and do an mvn clean install on it. Here's a sample app, built using Angular JS and Spring Boot.
Please do get in touch with feedback / questions / problems (best by email info at graphaware dot com). Cheers!
I suggest you wait a bit until SDN4 Milestone 1 comes out (developed by GraphAware) this was written from scratch for Neo4j-Server.
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).
Maybe a silly question :)
If we use separate physical servers for Application and Database, when using Traversal framework, which one of the servers should support the queries (DB or Application)?
Neo4j traversals run on the Neo4j database server, if you are using the server version of Neo4j.
Disclaimer: I'm building a similar system right now, so my view is probably biased.
My Node.js Application server provides an Angular app from the /public folder. The client application speaks only to the Application server.
Generally it works like this:
Client sends a message to Server.
Server returns a promise to client.
Server queries the DB, performs any necessary manipulation to the data.
Server resolves the promise.
Client interprets the response.
hope that's helpful.
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.