Unmaintained

When Neo4j 3.1 was introduced, it also came along with a new clustering protocol, bolt+routing://. We believe that the new casual cluster protocol is superior to the high availability one and we switched to the new official driver from neo4j (found here), thus deprecating this one.

If you are still using this driver wrapper, we are happy to receive PR's to make it better.

Neo4j High Availability Bolt Javascript Driver

Neo4j cluster session and transparent failover

About

This driver is a wrapper over the official Neo4j bolt driver and adds a layer of High Availability and transparent failovers

How to install

npm i --save neo4j-ha-bolt-driver

Quick example

const servers = [
    ['http://127.0.0.1:7474', 'bolt://127.0.0.1:7687'],
    ['http://127.0.0.1:7475', 'bolt://127.0.0.1:7688']
];

const auth = { user: 'neo4j', pass: 'password' };
const strategy = Neo4jHA.HAStrategies.roundRobin;
const rwConfig = Neo4jHA.HAReadWrite.masterReadWriteSlaveRead;
const checkInterval = 500;

console.log('connecting...');
const driver = new Neo4jHA(servers, { auth, strategy, rwConfig, checkInterval }, () => {
    console.log('ready');
    let session;
  
    // we get a session and we tell the driver that we will perform at least one write
    // the strategy is Round Robin but because we want to write 
    // and the read/write config is set to masterReadWriteSlaveRead (only master can write) 
    // this means that it will get a session to the master 
    session = driver.session(true);
    
    // don't forget to close sessions when you're done with them
    session.close();
    
    // now we request a read-only session, so all servers are eligible for conenctions
    // the first server in the list is chosen
    session = driver.session(false);
    session.close();
    
    // requesting another read-only session will choose the second server
    // because of the Round Robin 
    session = driver.session();
    session.close();

    // when you are done with the driver, just close it
    driver.close();
})

---

Enums

HAStrategies

• random: It will pick a random server from the pool
• roundRobin: It will round robin through the server pool
• nearest: It will pick the server with the lowest latency

HAReadWrite

• masterOnly: Master will be the only queried server
• masterWriteOnlySlaveReadOnly: Master is write-only and slaves are read-only
• masterReadWriteSlaveRead: Master is read-write and slaves are read-only
• all: All servers are read-write
• Custom HAReadWrite Structure

{
        master: { read: Boolean, write: Boolean },
        slave: { read: Boolean, write: Boolean }
}

Status

• error (-2): Server is returning an error in the HA check
• unknown (-1): Server is in an unknown state
• down ( 0): Server is unreachable
• up ( 1): Server is in the cluster

ServerType

• unknown ( 0): Server is in an unknown state
• slave ( 1): Server is a slave
• master ( 2): server is master

---

Instantiating a driver

const driver = new Neo4jHA(serverList, options, readyCallback);

Where:

• serverList: is an array of
  • [HTTP URL, BOLT URL]
  • {bolt: Bolt URL, url: HTTP URL, auth: {user, pass}}
• options:
  • auth: {user, pass} - for all the connections
  • strategy: HAStrategies
  • rwConfig: HAReadWriteConfig
  • neo4jDriverOptions: options passed on the the raw neo4j bolt driver
  • checkInterval: interval to check servers availability
  • retryOnError: number of times to retry the query until the error is surfaced in callback
  • badConnectionsCountAsErrors: true if a server connection error is counted as an error
• readyCallback: callback when all servers status is known

Usage

const session = driver.session(writeLock[, rwConfig, strategy]);

Where:

• writeLock: Boolean - Tell the driver ifif there will ve any writes in the session
• rwConfig: custom HAReadWriteConfig for that session
• strategy: custom HAStrategies for that session

---

License

License can be found here