Connection Heartbeat

The Ruby driver sends periodic hearbeats to the Cassandra server to check if the connection is alive. The heartbeat interval and the timeout is adjustable when creating a new Cassandra::Cluster. If a heartbeat is not returned, the connection will be considered dead and is closed automatically.

Background

Given

a running cassandra cluster with schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};

And

a file named “printing_listener.rb” with:

class PrintingListener
  def initialize(io)
    @out = io
  end

  def host_found(host)
    @out.puts("Host #{host.ip} is found")
  end

  def host_lost(host)
    @out.puts("Host #{host.ip} is lost")
  end

  def host_up(host)
    @out.puts("Host #{host.ip} is up")
  end

  def host_down(host)
    @out.puts("Host #{host.ip} is down")
  end
end

And

the following example:

require 'printing_listener'
require 'cassandra'

policy  = Cassandra::LoadBalancing::Policies::RoundRobin.new
policy  = Cassandra::LoadBalancing::Policies::WhiteList.new(['127.0.0.3'], policy)
cluster = Cassandra.cluster(
  heartbeat_interval:    2,
  idle_timeout:          5,
  hosts:                 '127.0.0.3',
  load_balancing_policy: policy
)
session = cluster.connect("simplex")

listener = PrintingListener.new($stderr)
cluster.register(listener)

$stdout.puts("=== START ===")
$stdout.flush
until (input = $stdin.gets).nil? # block until closed
  query = input.chomp
  begin
    results = session.execute(query)
    puts results.inspect
    execution_info = results.execution_info
    $stdout.puts("Query #{query.inspect} fulfilled by #{execution_info.hosts}")
  rescue => e
    $stdout.puts("#{e.class.name}: #{e.message}")
  end
  $stdout.flush
end
$stdout.puts("=== STOP ===")
$stdout.flush

And

it is running interactively

And

I wait for its output to contain “START”

And

node 3 is unreachable

Executing a query when a host is unreachable

When

I type “CREATE TABLE simplex.users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT)”

And

I close the stdin stream

Then

its output should contain:

Cassandra::Errors::NoHostsAvailable: All attempted hosts failed: 127.0.0.3 (Cassandra::Errors::IOError: Terminated due to inactivity)

Receiving notification that an unreachable host is down

When

I wait for 5 seconds

And

I close the stdin stream

Then

its output should contain:

Host 127.0.0.3 is down