A thread safe Ruby client for the NATS messaging system written in pure Ruby.
gem install nats-purerequire 'nats/client'
nats = NATS.connect("demo.nats.io")
puts "Connected to #{nats.connected_server}"
# Simple subscriber
nats.subscribe("foo.>") { |msg, reply, subject| puts "Received on '#{subject}': '#{msg}'" }
# Simple Publisher
nats.publish('foo.bar.baz', 'Hello World!')
# Unsubscribing
sub = nats.subscribe('bar') { |msg| puts "Received : '#{msg}'" }
sub.unsubscribe()
# Requests with a block handles replies asynchronously
nats.request('help', 'please', max: 5) { |response| puts "Got a response: '#{response}'" }
# Replies
sub = nats.subscribe('help') do |msg|
puts "Received on '#{msg.subject}': '#{msg.data}' with headers: #{msg.header}"
msg.respond("I'll help!")
end
# Request without a block waits for response or timeout
begin
msg = nats.request('help', 'please', timeout: 0.5)
puts "Received on '#{msg.subject}': #{msg.data}"
rescue NATS::Timeout
puts "nats: request timed out"
end
# Request using a message with headers
begin
msg = NATS::Msg.new(subject: "help", headers: {foo: 'bar'})
resp = nats.request_msg(msg)
puts "Received on '#{resp.subject}': #{resp.data}"
rescue NATS::Timeout => e
puts "nats: request timed out: #{e}"
end
# Server roundtrip which fails if it does not happen within 500ms
begin
nats.flush(0.5)
rescue NATS::Timeout
puts "nats: flush timeout"
end
# Closes connection to NATS
nats.closeIntroduced in v2.0.0 series, the client can now publish and receive messages from JetStream.
require 'nats/client'
nc = NATS.connect("nats://demo.nats.io:4222")
js = nc.jetstream
js.add_stream(name: "mystream", subjects: ["foo"])
Thread.new do
loop do
# Periodically publish messages
js.publish("foo", "Hello JetStream!")
sleep 0.1
end
end
psub = js.pull_subscribe("foo", "bar")
loop do
begin
msgs = psub.fetch(5)
msgs.each do |msg|
msg.ack
end
rescue NATS::IO::Timeout
puts "Retry later..."
end
endrequire 'nats/client'
cluster_opts = {
servers: ["nats://127.0.0.1:4222", "nats://127.0.0.1:4223"],
dont_randomize_servers: true,
reconnect_time_wait: 0.5,
max_reconnect_attempts: 2
}
nats = NATS.connect(cluster_opts)
puts "Connected to #{nats.connected_server}"
nats.on_error do |e|
puts "Error: #{e}"
end
nats.on_reconnect do
puts "Reconnected to server at #{nats.connected_server}"
end
nats.on_disconnect do
puts "Disconnected!"
end
nats.on_close do
puts "Connection to NATS closed"
end
nats.subscribe("hello") do |msg|
puts "#{Time.now} - Received: #{msg.data}"
end
n = 0
loop do
n += 1
nats.publish("hello", "world.#{n}")
sleep 0.1
endIt is possible to setup a custom TLS connection to NATS by passing an OpenSSL context to the client to be used on connect:
tls_context = OpenSSL::SSL::SSLContext.new
tls_context.ssl_version = :TLSv1_2
NATS.connect({
servers: ['tls://127.0.0.1:4444'],
reconnect: false,
tls: {
context: tls_context
}
})Since NATS Server v2.2 it is possible to connect to a NATS server using WebSocket.
-
Add a
websocketgem to your Gemfile:# Gemfile gem 'websocket'
-
Connect to WebSocket-enabled NATS Server using
wsorwssprotocol in URLs (for plain and secure connection respectively):nats = NATS.connect("wss://demo.nats.io:8443")
-
Use NATS as usual.
This requires server with version >= 2.0.0
Starting from v0.6.0 release of the client, you can also optionally install NKEYS in order to use the new NATS v2.0 auth features:
gem install nkeysNATS servers have a new security and authentication mechanism to authenticate with user credentials and NKEYS. A single file containing the JWT and NKEYS to authenticate against a NATS v2 server can be set with the user_credentials option:
NATS.connect("tls://connect.ngs.global", user_credentials: "/path/to/creds")This will create two callback handlers to present the user JWT and sign the nonce challenge from the server. The core client library never has direct access to your private key and simply performs the callback for signing the server challenge. The library will load and wipe and clear the objects it uses for each connect or reconnect.
Bare NKEYS are also supported. The nkey seed should be in a read only file, e.g. seed.txt.
> cat seed.txt
# This is my seed nkey!
SUAGMJH5XLGZKQQWAWKRZJIGMOU4HPFUYLXJMXOO5NLFEO2OOQJ5LPRDPMThen in the client specify the path to the seed using the nkeys_seed option:
NATS.connect("tls://connect.ngs.global", nkeys_seed: "path/to/seed.txt")By default, when you connect to a NATS server that's in a cluster, the client will take information about servers it doesn't know about yet. This can be disabled at connection time:
NATS.connect(servers: ['nats://127.0.0.1:4444'], ignore_discovered_urls: true)Using NATS within a Ractor requires URI 0.11.0 or greater to be installed.
Ractor.new do
ractor_nats = NATS.connect('demo.nats.io')
ractor_nats.subscribe('foo') do |msg, reply|
puts "Received on '#{msg.subject}': '#{msg.data}' with headers: #{msg.header}"
ractor_nats.publish(reply, 'baz')
end
sleep
end
nats = NATS.connect('demo.nats.io')
response = nats.request('foo', 'bar', timeout: 0.5)
puts response.dataUnless otherwise noted, the NATS source files are distributed under the Apache Version 2.0 license found in the LICENSE file.