Newque Ruby Client library
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README.md

Newque-ruby

Official gem for Newque. It offers a high level interface that is fully asynchronous and non-blocking.

See the Newque documentation for more information about configuring Newque for your use case.

Install

Requirements:

  • libffi
  • libzmq

Mac:

brew install libffi zeromq

Linux:

sudo apt-get install libffi-dev libzmq5

Then add gem 'newque' to your Gemfile.

Client

A Client is the main way to interact with Newque. Clients can send requests to Newque (Write, Read, Count, etc.) and receive responses for those requests. Every operation is concurrent, meaning that you can send multiple requests at the same time and wait until they all complete. These requests will be executing in parallel in the background. Read the short Newque-Ruby Concurrency Guide for a refresher on concurrency in Ruby.

Newque::Client.new(protocol, host, port, protocol_options:, timeout:)
# Example values
client = Newque::Client.new(:http, '127.0.0.1', 8005, protocol_options:{https: true}, timeout:5000)

These 3 arguments are required:

  • protocol: (:zmq or :http) Must match the protocol used by the Newque server.
  • host: (String) Hostname/IP address of the Newque server.
  • port: (Integer) Port of the Newque server.

Additionally, you can supply these optional named arguments:

  • protocol_options: (Hash) Optional named argument. The valid options depend on the protocol being used. See ZMQ Options and HTTP Options.
  • timeout (Integer) Optional named argument. Number of milliseconds to wait before cancelling for an operation to receive a response from the server. 10000 by default. At the moment only HTTP uses this value. Since all operations return Threads, it's also possible to use Ruby's .join(1) on a response thread to wait for 1 second. Newque-Ruby Concurrency Guide

Client methods

.write

result = client.write(channel, atomic, messages)
result.value # => waits until the call completes and returns a Newque::Write_Response
  • channel (String) Name of the channel.
  • atomic (Bool) Whether the messages should be treated as one.
  • messages (Array of Strings) The messages to send.

Returns a Future. The value returned by the Future will be a Newque::Write_Response.

.read

result = client.read(channel, mode, limit)
result.value # => waits until the call completes and returns a Newque::Read_Response
  • channel (String) Name of the channel.
  • mode (String) Newque Reading Mode.
  • limit (Optional Integer) The maximum number of messages to receive. nil by default.

Returns a Future. The value returned by the Future will be a Newque::Read_Response.

.read_stream

enumerable = client.read_stream(channel, mode, limit)
  • channel (String) Name of the channel.
  • mode (String) Newque Reading Mode.
  • limit (Optional Integer) The maximum number of messages to receive. nil by default.

Not available on :zmq clients! It takes the same arguments as read and returns a Lazy Enumerable. It'll stream the messages from Newque only when requested, for example by doing .each or any other standard method supported by Enumerables. It only holds a small number of messages at a time in memory (configurable on the server), making this a convenient way to iterate through a large dataset without having to make multiple read calls. It uses HTTP's Transfer-Encoding: Chunked. For obvious reasons it's not possible to know how many messages will be returned until the stream is exhausted by iterating through the entire Enumerable.

.count

result = client.count(channel)
result.value # => waits until the call completes and returns a Newque::Count_Response
  • channel (String) Name of the channel.

Returns a Future. The value returned by the Future will be a Newque::Count_Response.

.delete

result = client.delete(channel)
result.value # => waits until the call completes and returns a Newque::Delete_Response
  • channel (String) Name of the channel.

Returns a Future. The value returned by the Future will be a Newque::Delete_Response.

.health

result = client.health(channel, global)
result.value # => waits until the call completes and returns a Newque::Health_Response
  • channel (String) Name of the channel.
  • global (Bool) Whether this health check should check all the channels on the server or just this one.

Returns a Future. The value returned by the Future will be a Newque::Health_Response.

Pubsub Client

A Pubsub Client is a special type of client that can listen to requests coming from a Newque Pubsub endpoint. These Pubsub Clients are the subscribers. It's possible to have any number of Pubsub Clients active at any time.

consumer = Newque::Pubsub_client.new(host, port, protocol_options:, socket_wait:)

The first 4 arguments are identical to a normal Client.

socket_wait: (Integer) Optional named argument. This is the maximum acceptable time it could take to disconnect from the server. 100 (ms) by default.

.subscribe

This is the main operation on a Pubsub Client.

ready = consumer.subscribe do |input|
  input.messages # => ['msg1', 'msg2']
  input.action # => Newque::Write_request or Newque::Read_request, etc.
end

sub_id = ready.value # Waits until we are connected and returns the sub_id

Each time a request is sent to the Pubsub endpoint, this block will be invoked. The input argument is an Input_request.

.subscribe takes a block and returns a Future that evaluates to a Subscription ID. That Sub ID can then be given to .unsubscribe later to deactivate this specific block.

The Future that was returned by .subscribe does not resolve until the block is actively listening, which can take a few milliseconds.

It's possible to call .subscribe on the same Pubsub Client many times to register multiple blocks. A Pubsub Client doesn't open a connection to the server until a block is registered.

.unsubscribe

consumer.unsubscribe(sub_id)

Removes the block passed earlier from the list of subscribers.

.add_error_handler

consumer.add_error_handler do |error|
  # Do something with error
end

.add_error_handler takes a single block and can be called multiple times to register multiple blocks. When exceptions are raised inside of a subscribed block they are passed to this error handling block. If no error handler is present when an exception is raised, it'll be printed using puts, so register an error handler if you wish to avoid this behavior!

.disconnect

consumer.disconnect

Disconnects the Pubsub Client within socket_wait milliseconds. All subscribed blocks are still present. To reconnect, simply .subscribe a new block (you can unsubscribe it later).

Fifo Client

A Fifo Client is a special type of client that can listen to requests coming from a Newque Fifo endpoint and send responses back! It's possible to have any number of Fifo Clients active at any time.

consumer = Newque::Fifo_client.new(host, port, protocol_options:, socket_wait:)

The first 4 arguments are identical to a normal Client.

socket_wait: (Integer) Optional named argument. This is the maximum acceptable time it could take to disconnect from the server. 100 (ms) by default.

.connect

This is the main operation on a Fifo Client.

ready = consumer.connect do |input|
  input.channel # => 'my_channel'
  input.messages # => ['msg1', 'msg2']
  input.action # => Newque::Write_request or Newque::Read_request, etc.

  # If `input.action` was a Newque::Write_request, then I must return a Newque::Write_response
  Newque::Write_response.new(5)
end

ready.join # Only needed if we wish to wait until the Fifo Client is ready

.connect takes a block that receives and processes Requests. That block must return a Response object that matches the type of the Request! Calling input.action.class is an easy to find out the type of the request.

To return an error to the client that sent the request to Newque, just raise an exception from within the block!

.connect returns a Future that resolves once the Fifo Client is fully connected. Calling .connect on a Fifo Client that is already connected will raise an exception.

.disconnect

consumer.disconnect

Disconnects the Fifo Client within socket_wait milliseconds. A Fifo Client can't be reconnected, make a new one instead.

Newque-Ruby Concurrency Guide

The Thread is Ruby's basic concurrency primitive. There is never more than one Ruby Thread executing Ruby code at any moment, but native extensions given their own Thread can continue running in the background while executing native (non-Ruby) code.

Newque-Ruby makes heavy use of Threads, since for example, a Pubsub Client waiting for requests should not "take up" your only allowed active Ruby Thread!

Most method calls on Newque-Ruby return a Future, which is just a simple object to manage the underlying Ruby Thread. If you are familiar with Promises in other languages, the Future objects returned by Newque-Ruby are very similar.

Most gems simply block and assume the user will wrap those blocking calls in a Thread.new if they feel brave. Due to the fact that a Newque::Client with ZMQ uses a single multiplexing connection (unlike HTTP) and that we want operations (writes, reads, etc.) -which can terminate in a different order- to be executed in parallel, Newque-Ruby operations have to return Futures that will resolve to the desired result. In order to keep Newque::Clients with HTTP identical to ZMQ ones, those return Futures too.

What you need to know:

To get the result of an operation, you have to call .get on the Future returned by Newque-Ruby.

  • client.delete('mychannel').get(limit) will wait for the Future returned by .delete to resolve for up to limit seconds. If it times out, .get will raise Timeout::Error.
  • The limit argument is optional, it defaults to the timeout value passed when creating the Client.
future1 = client.write('channel_a', false, ['msg1'])
future2 = client.write('channel_b', false, ['msg1'])

result1 = future1.get
result2 = future1.get

# Do something with the results

This snippet makes 2 calls in parallel and waits until both have completed to continue.

Protocol Options

HTTP Options

Option Type Required Default Description
https Bool No false Whether to use HTTPS or not.
http_format :json or :plaintext No :json Must match the HTTP Format configured in Newque. json by default.
separator String No "\n" Must match the separator string configured in Newque. "\n" by default.

ZMQ Options

(IMPORTANT: Read the docs before changing any defaults!)

Option Type Required Default Description
ZMQ_MAXMSGSIZE Integer No -1 Max message size in bytes, -1 means unlimited.
ZMQ_LINGER Integer No 60000 How long to keep unaccepted messages after disconnection in milliseconds.
ZMQ_RECONNECT_IVL Integer No 100 Reconnection interval in milliseconds.
ZMQ_RECONNECT_IVL_MAX Integer No 60000 Max exponential backoff reconnection interval in milliseconds.
ZMQ_BACKLOG Integer No 100 The backlog argument for the listen(2) syscall.
ZMQ_SNDHWM Integer No 5000 Hard limit on the number outbound outstanding messages per connection.
ZMQ_RCVHWM Integer No 5000 Hard limit on the number inbound outstanding messages per connection.

Response objects

These objects are returned by method calls on a Newque::Client. Additionally, they are what a Newque::Fifo_client must return to the server.

Write_response

response = Newque::Write_response.new(5)
response.saved # => 5

Read_response

response = Newque::Read_response.new(2, 'some-id', 12345678, ['msg1', 'msg2'])
response.length # => 2
response.last_id # => 'some-id'
response.last_timens # => '12345678'
response.messages # => ['msg1', 'msg2']

Count_response

response = Newque::Count_response.new(8)
response.count # => 8

Delete_response

response = Newque::Delete_response.new

Health_response

response = Newque::Health_response.new

Request objects

Newque::Fifo_clients and Newque::Pubsub_clients receive an Input_request when a request is received on a channel with Backend of that type.

Input_request

request.channel # => 'my_channel'
request.messages # => ['msg1', 'msg2']
request.action # => Newque::Write_request or Newque::Read_request, etc.

Write_request

request = Newque::Write_request.new(false, ['id1', 'id2'])
request.atomic # => false
request.ids # => ['id1', 'id2']

Read_request

request = Newque::Read_request.new('after_id some-id', '100')
request.mode # => 'after_id some-id'
request.limit # => 100

Count_request

request = Newque::Count_request.new

Delete_request

request = Newque::Delete_request.new

Health_request

request = Newque::Health_request.new(false)
request.global # => false

Running the tests

Make sure the Gem dev dependencies are installed first.

You'll need 2 terminals windows!

# In terminal 1
docker pull newque/newque:v0.0.5

docker run -it -p 8000:8000 -p 8001:8001 -p 8005:8005 -p 8006:8006 -p 8007:8007 newque/newque:v0.0.5 bash
cd newque
rm -r conf

# Switch to terminal 2

# Grab the Container ID:
docker ps

# Replace the CONTAINER_ID in this command and make sure you're in the newque-ruby/ directory:
docker cp conf CONTAINER_ID:/newque/conf

# Go back to terminal 1
./newque

# Switch to terminal 2
bundle exec rake