Datastax Ruby Driver for Apache Cassandra

If you're reading this on GitHub, please note that this is the readme for the development version and that some features described here might not yet have been released. You can view the documentation for the latest released version here.

A Ruby client driver for Apache Cassandra. This driver works exclusively with the Cassandra Query Language version 3 (CQL3) and Cassandra's native protocol.

• Code: https://github.com/datastax/ruby-driver
• Docs: http://docs.datastax.com/en/developer/ruby-driver
• Jira: https://datastax-oss.atlassian.net/browse/RUBY
• Mailing List: https://groups.google.com/a/lists.datastax.com/forum/#!forum/ruby-driver-user
• IRC: #datastax-drivers on irc.freenode.net
• Twitter: Follow the latest news about DataStax Drivers - @stamhankar999, @avalanche123, @al3xandru

This driver is based on the cql-rb gem by Theo Hultberg and we added support for:

• Asynchronous execution
• One-off, prepared and batch statements
• Automatic peer discovery and cluster metadata with support for change notifications
• Various load-balancing, retry and reconnection policies with ability to write your own
• SSL encryption
• Flexible and robust error handling
• Per-request execution information and tracing
• Configurable address resolution

Check out the slides from Ruby Driver Explained for a detailed overview of the Ruby Driver architecture.

Compatibility

This driver works exclusively with the Cassandra Query Language v3 (CQL3) and Cassandra's native protocol. The current version works with:

• Apache Cassandra versions 1.2, 2.0, 2.1, 2.2, and 3.x
• DataStax Enterprise 4.0 and above.
• Ruby (MRI) 2.2, 2.3
• JRuby 1.7

Note: JRuby 1.6 is not officially supported, although 1.6.8 should work. Rubinius is not supported. MRI 2.0, 2.1, and JRuby 9k are not officially supported, but they should work. 1.9.3 is deprecated and is likely to break in the release following 3.0.

Feedback Requested

Help us focus our efforts! Provide your input on the Ruby Driver Platform and Runtime Survey (we kept it short).

Quick start

require 'cassandra'

cluster = Cassandra.cluster # connects to localhost by default

cluster.each_host do |host| # automatically discovers all peers
  puts "Host #{host.ip}: id=#{host.id} datacenter=#{host.datacenter} rack=#{host.rack}"
end

keyspace = 'system_schema'
session  = cluster.connect(keyspace) # create session, optionally scoped to a keyspace, to execute queries

future = session.execute_async('SELECT keyspace_name, table_name FROM tables') # fully asynchronous api
future.on_success do |rows|
  rows.each do |row|
    puts "The keyspace #{row['keyspace_name']} has a table called #{row['table_name']}"
  end
end
future.join

Note: The host you specify is just a seed node, the driver will automatically discover all peers in the cluster.

Read more:

• Cassandra.cluster options
• Session#execute_async options
• Usage documentation

Installation

Install via rubygems

gem install cassandra-driver

Install via Gemfile

gem 'cassandra-driver'

Note: if you want to use compression you should also install snappy or lz4-ruby. Read more about compression.

Upgrading from cql-rb

Some of the new features added to the driver have unfortunately led to changes in the original cql-rb API. In the examples directory, you can find an example of how to wrap the ruby driver to achieve almost complete interface parity with cql-rb to assist you with gradual upgrade.

What's new in v3.1

This minor release introduces features and fixes around resiliency, schema metadata, usability, and performance. One of the most user-impacting of these is the introduction of execution profiles. Execution profiles allow you to group various execution options into a 'profile' and you reference the desired profile at execution time. Get the scoop here.

See the changelog for more information on all changes in this version and past versions.

What's new in v3.0

Features:

• Add support for Apache Cassandra native protocol v4
• Add support for smallint, tinyint, date (Cassandra::Date) and time (Cassandra::Time) data types.
• Include schema metadata for User Defined Functions and User Defined Aggregates.
• Augment the Cassandra::Table object to expose many more attributes: id, options, keyspace, partition_key, clustering_columns, and clustering_order. This makes it significantly easier to write administration scripts that report various attributes of your schema, which may help to highlight areas for improvement.
• Include client ip addresses in request traces, only on Cassandra 3.x.
• Add new retry policy decision Cassandra::Retry::Policy#try_next_host.
• Support specifying statement idempotence with the new idempotent option when executing.
• Support sending custom payloads when preparing or executing statements using the new payload option.
• Expose custom payloads received with responses on server exceptions and Cassandra::Execution::Info instances.
• Expose server warnings on server exceptions and Cassandra::Execution::Info instances.
• Add connections_per_local_node, connections_per_remote_node, requests_per_connection cluster configuration options to tune parallel query execution and resource usage.
• Add Cassandra::Logger class to make it easy for users to enable debug logging in the client.
• Add protocol_version configuration option to allow the user to force the protocol version to use for communication with nodes.
• Add support for materialized views and indexes in the schema metadata.
• Support the ReadError, WriteError, and FunctionCallError Cassandra error responses introduced in Cassandra 2.2.
• Add support for unset variables in bound statements.
• Support DSE security (DseAuthenticator, configured for LDAP).
• Add a timeout option to Cassandra::Future#get.

Breaking Changes from 2.x:

• Cassandra::Future#join is now an alias to Cassandra::Future#get and will raise an error if the future is resolved with one.
• Default consistency level is now LOCAL_ONE.
• Enable tcp no-delay by default.
• Unavailable errors are retried on the next host in the load balancing plan by default.
• Statement execution no longer retried on timeouts, unless the statement is marked as idempotent in the call to Cassandra::Session#execute* or when creating a Cassandra::Statement object.
• Cassandra::Statements::Batch#add and Cassandra::Session#execute* signatures have changed in how one specifies query parameters. Specify the query parameters array as the value of the arguments key:

batch.add(query, ['val1', 'val2'])
# becomes
batch.add(query, arguments: ['val1', 'val2'])

batch.add(query, {p1: 'val1'})
# becomes
batch.add(query, arguments: {p1: 'val1'})

• The Datacenter-aware load balancing policy (Cassandra::LoadBalancing::Policies::DCAwareRoundRobin) defaults to using nodes in the local DC only. In prior releases, the policy would fall back to remote nodes after exhausting local nodes. Specify a positive value (or nil for unlimited) for max_remote_hosts_to_use when initializing the policy to allow remote node use.
• Unspecified variables in statements previously resulted in an exception. Now they are essentially ignored or treated as null.

Bug Fixes:

• [RUBY-120] Tuples and UDTs can be used in sets and hash keys.
• [RUBY-143] Retry querying system table for metadata of new hosts when prior attempts fail, ultimately enabling use of new hosts.
• [RUBY-150] Fixed a protocol decoding error that occurred when multiple messages are available in a stream.
• [RUBY-151] Decode incomplete UDTs properly.
• [RUBY-155] Request timeout timer should not include request queuing time.
• [RUBY-161] Protocol version negotiation in mixed version clusters should not fall back to v1 unless it is truly warranted.
• [RUBY-214] Ensure client timestamps have microsecond precision in JRuby. Previously, some row updates would get lost in high transaction environments.

Code examples

The DataStax Ruby Driver uses the awesome Cucumber Framework for both end-to-end, or acceptance, testing and constructing documentation. All of the features supported by the driver have appropriate acceptance tests with easy-to-copy code examples in the features/ directory.

Running tests

If you don't feel like reading through the following instructions on how to run ruby-driver tests, feel free to check out .travis.yml for the entire build code.

• Check out the driver codebase and install test dependencies:

git clone https://github.com/datastax/ruby-driver.git
cd ruby-driver
bundle install --without docs

• Install ccm

• Run tests against different versions of Cassandra:

CASSANDRA_VERSION=3.1.1 bundle exec cucumber # runs end-to-end tests (or bundle exec rake cucumber)
CASSANDRA_VERSION=3.0.0 bundle exec rspec # runs unit tests (or bundle exec rake rspec)
CASSANDRA_VERSION=2.1.12 bundle exec rake integration # run integration tests
CASSANDRA_VERSION=2.0.17 bundle exec rake test # run both as well as integration tests

Changelog & versioning

Check out the releases on GitHub and changelog. Version numbering follows the semantic versioning scheme.

Private and experimental APIs, defined as whatever is not in the public API documentation, i.e. classes and methods marked as @private, will change without warning. If you've been recommended to try an experimental API by the maintainers, please let them know if you depend on that API. Experimental APIs will eventually become public, and knowing how they are used helps in determining their maturity.

Prereleases will be stable, in the sense that they will have finished and properly tested features only, but may introduce APIs that will change before the final release. Please use the prereleases and report bugs, but don't deploy them to production without consulting the maintainers, or doing extensive testing yourself. If you do deploy to production please let the maintainers know as this helps in determining the maturity of the release.

Known bugs & limitations

• Specifying a protocol_version option of 1 or 2 in cluster options will fail with a NoHostsAvailable error rather than a ProtocolError against Cassandra node versions 3.0-3.4.
• JRuby 1.6 is not officially supported, although 1.6.8 should work.
• Because the driver reactor is using IO.select, the maximum number of tcp connections allowed is 1024.
• Because the driver uses IO#write_nonblock, Windows is not supported.

Please refer to the usage documentation for more information on common pitfalls

Contributing

For contributing read CONTRIBUTING.md

Credits

This driver is based on the original work of Theo Hultberg on cql-rb and adds a series of advanced features that are common across all other DataStax drivers for Apache Cassandra.

The development effort to provide an up to date, high performance, fully featured Ruby Driver for Apache Cassandra will continue on this project, while cql-rb has been discontinued.

Copyright

Copyright 2013-2016 DataStax, Inc.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.