Crystal NATS

The Crystal client for the NATS Messaging System.

Installation

Add this to your application's shard.yml:

dependencies:
  nats:
    github: SlayerShadow/crystal-nats

Basic usage

• Because of the module doesn't know which data will be received (text? binary?), the incoming "message" type is always set to Bytes (see Crystal Thread for more details).

require "nats"

client = NATS::Client.new
# There can be passed options (see below)
client.connect

# Simple subscription (message: Bytes)
client.subscribe("foo"){ |message| puts "Message: #{ String.new message }" }

# Unsubscribe
sid = client.subscribe("foo"){ |message| puts "Message: #{ String.new message }" }
cluent.unsubscribe sid

# Reply (message: Bytes, reply: String)
client.subscribe("foo"){ |message, reply| puts "Replying to: #{ reply }" }

# Matches subject (message: Bytes, reply: String, subject: String)
client.subscribe("foo.*"){|message, reply, subject|
  puts "Receiving from: #{ subject }"
}

# Publish into the channel (channel: String, message: String)
client.publish("foo", "bar")

# Publish with reply (channel: String, message: String, reply: String)
client.publish("foo", "bar", "foo.repl")

Clustered usage (not fully implemented)

require "nats"

options = NATS::Client::OptionsHash{
  :servers => [ "nats://localhost:4222", "nats://localhost:4223" ],
  :randomize_servers => true, # Should servers be chosen randomly
  :reconnect => true, # Tries to reconnect to server after failed attempt
  :max_reconnect_attempts => 10u8, # How many times try to reconnect before exception
  :reconnect_time_wait => 2u8, # Delay between reconnection tries
  :verbose => true # if need to confirm that sent is succeeded
}

client = NATS::Client.new
client.connect options

client.subscribe("foo"){|message, reply, subject|
  # Do something
}

Authentication

require "nats"

options = NATS::Client::OptionsHash{
  :servers => [ "nats://localhost:4222" ],
  :user => "name",
  :pass => "helloworld"
}

client = NATS::Client.new
client.connect options

TLS

require "nats"

options = NATS::Client::OptionsHash{
  :servers => [ "tls://localhost:4444" ],
  :tls => {
    :cert_file => "config/cert.pem",
    :cert_key_file => "config/cert/key.pem",
    :ca_cert_file => "config/ca.pem", # When need to verify peer
    :verify_peer => false             # Along with ca_cert_file - when need to verify peer (default - false)
  }
}

client = NATS::Client.new
client.connect options

Note that:

• If NATS launched with -tlsverify
  • It should be also launched with at least -tlscert, -tlskey and -tlscacert.
  • App should be started with at least :cert_key_file and :ca_cert_file.
• If NATS launched without tlsverify
  • It can be also launched without -tlscacert.
  • App can be started even without :tls key (protocol will be switched to TLS transparently).
• If app launches with :verify_peer => true
  • NATS can be launched without -tlscacert but the -tlscert and -tlskey should be passed.
  • App should be started with :ca_cert_file to verify NATS.
  • App can be started without :cert_file and :cert_key_file (only CA is mandatory).
• If NATS launched with -tlsverify and app launches with :verify_peer => true
  • NATS and app should be fully configured for TLS connection.

Development

Features

• Exchange server messages
  • Tests
• Clusterization
  • Tests
• Publish/Subscribe
  • on_error callback
  • on_disconnect callback
  • on_reconnect callback
  • on_close callback
  • Tests
• Unsubscribe
  • Unsubscribe after receiving amount of messages
  • Tests
• Reconnect after critical errors
  • Tests
• User authentication
  • Tests
• OpenSSL
  • Connect with using certificates
  • Manage server information to determine when to connect through SSL
  • Tests
• Subscriptions timeouts
  • Tests

Improvements

• Make the "options" flexible
  • Hash
  • JSON::Any
  • YAML::Any
    • Require yaml in macros and only when it needed (lazy)
• Add configuration for channel buffer (see Crystal thread)

Performance

• Remove regex from parser
• Manage Bytes only, even when receive protocol commands

Contributing

1. Fork it ( https://github.com/SlayerShadow/crystal-nats/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• SlayerShadow Dmitry Lykov - creator, maintainer