Cassandra status check using nodejs

问题

I use the nodejs in three environments and the Cassandra is running in all the three nodes.

I totally understand using nodetool status I will be able to get the status of each node. But the problem is If my current node is down then I will not be able to perform nodetool status in the current node, So Is there a way to get the status using nodejs Cassandra driver?

Any help is appreciated.

EDITED :

As per dilsingi's suggestion, I used the client.hosts but the problem is, In the following cluster, 172.30.56.61 is down still it is showing as available. How to get the status of each node?

const cassandra = require('cassandra-driver');
const client = new cassandra.Client({ contactPoints: ['172.30.56.60','172.30.56.61','172.30.56.62'], keyspace: 'test', policies : { loadBalancing : new cassandra.policies.loadBalancing.RoundRobinPolicy }});

    async function read() {
        client.connect().then(function () {
          console.log('Connected to cluster with %d host(s): %j', client.hosts.length, client.hosts.keys());
          client.hosts.forEach(function (host) {
       console.log(host.address, host.datacenter, host.rack);
    });

        });
    }

    read();

nodeTool status output :

Datacenter: newyork
===================
Status=Up/Down

    |/ State=Normal/Leaving/Joining/Moving
    --  Address       Load       Tokens       Owns (effective)  Host ID                               Rack
    UN  172.30.56.62  1.13 MiB   256          34.8%             e93827b7-ba43-4fba-8a51-4876832b5b22  rack1
    DN  172.30.56.60  1.61 MiB   256          33.4%             e385af22-803e-4313-bee2-16219f73c213  rack1
    UN  172.30.56.61  779.4 KiB  256          31.8%             be7fc52e-c45d-4380-85a3-4cbf6d007a5d  rack1


Node Js Code :

    const cassandra = require('cassandra-driver');
    const client = new cassandra.Client({ contactPoints: ['172.30.56.60','172.30.56.61','172.30.56.62'], keyspace: 'qcs', policies : { loadBalancing : new cassandra.policies.loadBalancing.RoundRobinPolicy }});

    async function read() {
        client.connect().then(function () {
          console.log('Connected to cluster with %d host(s): %j', client.hosts.length, client.hosts.keys());
          client.hosts.forEach(function (host) {
               console.log(host.address, host.datacenter, host.rack, host.isUp(), host.canBeConsideredAsUp());
          });

        });
    }

    read();

NodeJs output :

    Connected to cluster with 3 host(s): ["172.30.56.60:9042","172.30.56.61:9042","172.30.56.62:9042"]
    172.30.56.60:9042 newyork rack1 true true
    172.30.56.61:9042 newyork rack1 true true
    172.30.56.62:9042 newyork rack1 true true

回答1:

The drivers in general including (nodejs) are aware of the entire Cassandra cluster Topology. Upon the initial contact with the one or more node ip address in connection string, driver can automatically identify all the node ips that make up the cassandra ring. Its intelligent enough to know when a node goes down or a new node joins the cluster. It can even continue working with completely new nodes (ips) than what it began with.

So there isn't a requirement to code for node status, as driver automatically handles that for you. Its recommended to provide more than 1 ip in the connection string, so as to provide redundancy while making initial connection.

Here is the nodejs driver documentation and this section describe the "Auto node discovery" feature and "Cluster & Schema Metadata".

来源：https://stackoverflow.com/questions/49276508/cassandra-status-check-using-nodejs

标签

node.js

cassandra

cassandra-3.0