Request Execution Errors

The Ruby driver will error out and provide error messages for various errors. Check out the request execution diagram in Error Handling guide and come back here for real-world examples of error handling.

Background

Given: a running cassandra cluster

Executing a statement with invalid syntax

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster
session = cluster.connect("simplex")

begin
  session.execute("INSERT INTO users (user_id, first, last, age)")
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::SyntaxError: line 0:-1 mismatched input '<EOF>' expecting K_VALUES\n

Connecting to non-existent keyspace

Given

the following example:

require 'cassandra'

cluster = Cassandra.cluster

begin
  session = cluster.connect("badkeyspace")
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::InvalidError: Keyspace 'badkeyspace' does not exist

Modifying system keyspace

Given

the following example:

require 'cassandra'

cluster = Cassandra.cluster
session = cluster.connect("system")

begin
  session.execute("CREATE TABLE users (user_id INT PRIMARY KEY)")
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::UnauthorizedError: system keyspace is not user-modifiable.

Dropping non-existent keyspace

Given

the following example:

require 'cassandra'

cluster = Cassandra.cluster
session = cluster.connect()

begin
  session.execute("DROP KEYSPACE badkeyspace")
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::ConfigurationError: Cannot drop non existing keyspace 'badkeyspace'.

Creating keyspace that already exists

Given

the following schema:

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

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster
session = cluster.connect()

begin
  session.execute("CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3}")
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::AlreadyExistsError: Cannot add existing keyspace "simplex"

Connecting with invalid authentication credentials

Given

a running cassandra cluster with authentication enabled

And

the following example:

require 'cassandra'

begin
  Cassandra.cluster(
    username: 'invalidname',
    password: 'badpassword'
  )
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::AuthenticationError: Username and/or password are incorrect

Connecting to unreachable cluster

Given

node 1 is unreachable

And

the following example:

require 'cassandra'

begin
  Cassandra.cluster(connect_timeout: 1)
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

it is executed

Then

its output should contain:

Cassandra::Errors::IOError: Could not connect to 127.0.0.1:9042 within 1s

Executing a statement when all hosts are down

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);
INSERT INTO users (user_id, first, last, age) VALUES (0, 'John', 'Doe', 40);
INSERT INTO users (user_id, first, last, age) VALUES (1, 'Mary', 'Doe', 35);
INSERT INTO users (user_id, first, last, age) VALUES (2, 'Agent', 'Smith', 32);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster(retry_policy: Cassandra::Retry::Policies::Fallthrough.new)
session = cluster.connect("simplex")

$stdout.puts("=== START ===")
$stdout.flush
until (input = $stdin.gets).nil? # block until closed
  query = input.chomp
  begin
    results = session.execute(query, consistency: :all, timeout: 2)
    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

When

it is running interactively

And

I wait for its output to contain “START”

And

all nodes are down

And

I type “SELECT * FROM simplex.users”

And

I close the stdin stream

Then

its output should contain:

Cassandra::Errors::NoHostsAvailable: All hosts down

Executing a statement when can’t achieve desired consistency

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster
session = cluster.connect("simplex")

query = "INSERT INTO users (user_id, first, last, age) VALUES (0, 'John', 'Doe', 40)"
begin
  session.execute(query, :consistency => :all)
rescue => e
  puts "#{e.class.name}: #{e.message}"
end

When

node 3 stops

And

it is executed

Then

its output should contain:

Cassandra::Errors::UnavailableError: Cannot achieve consistency level ALL

Executing a SELECT statement when replica times out

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);
INSERT INTO users (user_id, first, last, age) VALUES (0, 'John', 'Doe', 40);
INSERT INTO users (user_id, first, last, age) VALUES (1, 'Mary', 'Doe', 35);
INSERT INTO users (user_id, first, last, age) VALUES (2, 'Agent', 'Smith', 32);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster(retry_policy: Cassandra::Retry::Policies::Fallthrough.new)
session = cluster.connect("simplex")

$stdout.puts("=== START ===")
$stdout.flush
until (input = $stdin.gets).nil? # block until closed
  query = input.chomp
  begin
    results = session.execute(query, consistency: :all, timeout: 2)
    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

When

it is running interactively

And

I wait for its output to contain “START”

And

node 3 is unreachable

And

I type “SELECT * FROM simplex.users”

And

I close the stdin stream

Then

its output should contain:

Cassandra::Errors::ReadTimeoutError: Operation timed out - received only 0 responses.

Executing an UPDATE statement when replica times out

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);
INSERT INTO users (user_id, first, last, age) VALUES (0, 'John', 'Doe', 40);
INSERT INTO users (user_id, first, last, age) VALUES (1, 'Mary', 'Doe', 35);
INSERT INTO users (user_id, first, last, age) VALUES (2, 'Agent', 'Smith', 32);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster(retry_policy: Cassandra::Retry::Policies::Fallthrough.new)
session = cluster.connect("simplex")

$stdout.puts("=== START ===")
$stdout.flush
until (input = $stdin.gets).nil? # block until closed
  query = input.chomp
  begin
    results = session.execute(query, consistency: :all, timeout: 2)
    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

When

it is running interactively

And

I wait for its output to contain “START”

And

node 3 is unreachable

And

I type “UPDATE simplex.users SET age=41 WHERE user_id=0”

And

I close the stdin stream

Then

its output should contain:

Cassandra::Errors::WriteTimeoutError: Operation timed out - received only 0 responses.

Truncating a table when replica times out

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);
INSERT INTO users (user_id, first, last, age) VALUES (0, 'John', 'Doe', 40);
INSERT INTO users (user_id, first, last, age) VALUES (1, 'Mary', 'Doe', 35);
INSERT INTO users (user_id, first, last, age) VALUES (2, 'Agent', 'Smith', 32);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster(retry_policy: Cassandra::Retry::Policies::Fallthrough.new)
session = cluster.connect("simplex")

$stdout.puts("=== START ===")
$stdout.flush
until (input = $stdin.gets).nil? # block until closed
  query = input.chomp
  begin
    results = session.execute(query, consistency: :all, timeout: 2)
    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

When

it is running interactively

And

I wait for its output to contain “START”

And

node 3 is unreachable

And

I type “TRUNCATE simplex.users”

And

I close the stdin stream

Then

its output should contain:

Cassandra::Errors::TruncateError: Error during truncate

Executing a statement when all nodes time out

Given

the following schema:

CREATE KEYSPACE simplex WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
USE simplex;
CREATE TABLE users (user_id BIGINT PRIMARY KEY, first VARCHAR, last VARCHAR, age BIGINT);
INSERT INTO users (user_id, first, last, age) VALUES (0, 'John', 'Doe', 40);
INSERT INTO users (user_id, first, last, age) VALUES (1, 'Mary', 'Doe', 35);
INSERT INTO users (user_id, first, last, age) VALUES (2, 'Agent', 'Smith', 32);

And

the following example:

require 'cassandra'

cluster = Cassandra.cluster(retry_policy: Cassandra::Retry::Policies::Fallthrough.new)
session = cluster.connect("simplex")

$stdout.puts("=== START ===")
$stdout.flush
until (input = $stdin.gets).nil? # block until closed
  query = input.chomp
  begin
    results = session.execute(query, consistency: :all, timeout: 2)
    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

When

it is running interactively

And

I wait for its output to contain “START”

And

all nodes are unreachable

And

I type “SELECT * FROM simplex.users WHERE user_id=0”

And

I close the stdin stream

Then

its output should contain:

Cassandra::Errors::NoHostsAvailable: All attempted hosts failed

And

its output should contain:

127.0.0.1 (Cassandra::Errors::TimeoutError: Timed out)

And

its output should contain:

127.0.0.2 (Cassandra::Errors::TimeoutError: Timed out)

And

its output should contain:

127.0.0.3 (Cassandra::Errors::TimeoutError: Timed out)

Request Execution Errors

Background

Executing a statement with invalid syntax

Connecting to non-existent keyspace

Modifying system keyspace

Dropping non-existent keyspace

Creating keyspace that already exists

Connecting with invalid authentication credentials

Connecting to unreachable cluster

Executing a statement when all hosts are down

Executing a statement when can’t achieve desired consistency

Executing a SELECT statement when replica times out

Executing an UPDATE statement when replica times out

Truncating a table when replica times out

Executing a statement when all nodes time out

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