使用 lambda 层连接到 AWS Keyspaces 时出错

Question

Intermittently getting the following error when connecting to an AWS keyspace using a lambda layer

All host(s) tried for query failed. First host tried, 3.248.244.53:9142: Host considered as DOWN. See innerErrors.

I am trying to query a table in a keyspace using a nodejs lambda function as follows:

import cassandra from 'cassandra-driver';
import fs from 'fs';

export default class AmazonKeyspace {

  tpmsClient = null;

  constructor () {
    let auth = new cassandra.auth.PlainTextAuthProvider('cass-user-at-xxxxxxxxxx', 'zzzzzzzzz');
    let sslOptions1 = {
      ca: [ fs.readFileSync('/opt/utils/AmazonRootCA1.pem', 'utf-8')],
      host: 'cassandra.eu-west-1.amazonaws.com',
      rejectUnauthorized: true
    };
    this.tpmsClient = new cassandra.Client({
      contactPoints: ['cassandra.eu-west-1.amazonaws.com'],
      localDataCenter: 'eu-west-1',
      authProvider: auth,
      sslOptions: sslOptions1,
      keyspace: 'tpms',
      protocolOptions: { port: 9142 }
    });
  }

  getOrganisation = async (orgKey) => {
    const SQL = 'select * FROM organisation where organisation_id=?;';

    return new Promise((resolve, reject) => {
      this.tpmsClient.execute(SQL, [orgKey], {prepare: true}, (err, result) => {
        if (!err?.message) resolve(result.rows);
        else reject(err.message);
      });
    });
  };
}

I am basically following this recommended AWS documentation. https://docs.aws.amazon.com/keyspaces/latest/devguide/using_nodejs_driver.html

It seems that around 10-20% of the time the lambda function (cassandra driver) cannot connect to the endpoint.

I am pretty familiar with Cassandra (I already use a 6 node cluster that I manage) and don't have any issues with that.

Could this be a timeout or do I need more contact points?

Followed the recommended guides. Checked from the AWS console for any errors but none shown.

UPDATE: Update to the above question....

I am occasionally (1 in 50 if I parallel call the function (5 concurrent calls)) getting the below error:

"All host(s) tried for query failed. First host tried, 3.248.244.5:9142: DriverError: Socket was closed at Connection.clearAndInvokePending (/opt/node_modules/cassandra-driver/lib/connection.js:265:15) at Connection.close (/opt/node_modules/cassandra-driver/lib/connection.js:618:8) at TLSSocket. (/opt/node_modules/cassandra-driver/lib/connection.js:93:10) at TLSSocket.emit (node:events:525:35)\n at node.net:313:12\n at TCP.done (node:_tls_wrap:587:7) { info: 'Cassandra Driver Error', isSocketError: true, coordinator: '3.248.244.5:9142'}

Answer 1

This exception may be caused by throttling in the keyspaces side, resulting the Driver Error that you are seeing sporadically.

I would suggest taking a look over this repo which should help you to put measures in place to either prevent the occurrence of this issue or at least reveal the true cause of the exception.

Answer 2

Some of the errors you see in the logs you will need to investigate Amazon CloudWatch metrics to see if you have throttling or system errors. I've built this AWS CloudFormation template to deploy a CloudWatch dashboard with all the appropriate metrics. This will provide better observability for your application.

A System Error indicates an event that must be resolved by AWS and often part of normal operations. Activities such as timeouts, server faults, or scaling activity could result in server errors. A User error indicates an event that can often be resolved by the user such as invalid query or exceeding a capacity quota. Amazon Keyspaces passes the System Error back as a Cassandra ServerError . In most cases this a transient error, in which case you can retry your request until it succeeds. Using the Cassandra driver's default retry policy customers can also experience NoHostAvailableException or AllNodesFailedException or messages like yours "All host(s) tried for query failed". This is a client side exception that is thrown once all host in the load balancing policy's query plan have attempted the request.

Take a look at this retry policy for NodeJs which should help resolve your "All hosts failed" exception or pass back the original exception.

The retry policies in the Cassandra drivers are pretty crude and will not be able to do more sophisticated things like circuit breaker patters. You may want to eventually use a "failfast" retry policy for the driver and handle the exceptions in your application code.