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Evil Martians
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Evil Martians
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What is
Action Cable?
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Action Cable
RailsConf 2015 April, 21
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Action Cable
RailsConf 2015
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Action Cable in a Nutshell
Server
Client
WebSocket
Client
WebSocket
stream C
Broadcaster
stream B
stream A
stream B
channel X
channel Y
channel Z
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Action Cable Channel
class AnswersChannel < ApplicationCable::Channel
def subscribed
reject_subscription unless current_user.admin?
end
def follow(params)
stream_from "questions/#{params['id']}"
end
end
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The Good Parts
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Good Parts
• Easy configuration
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Good Parts
• Easy configuration
• Application logic access through
channels
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Good Parts
• Easy configuration
• Application logic access through
channels
• JavaScript client that just works
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Bad Parts?
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Performance
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Memory Cable
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Memory Cable
20k connections
MB
0
375
750
1 125
1 500
1 875
2 250
2 625
3 000
Go Erlang ActionCable (2x) ActionCable (16x)
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WebSocket Shootout
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WebSocket Shootout
Client
Server
broadcast
to all
message
send message back
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WebSocket Shootout
Broadcast RTT
0s
1s
2s
3s
4s
5s
6s
7s
8s
9s
10s
Number of connections
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Go Erlang ActionCable
Running on AWS EC2 c3.4xlarge (16 vCPU, 30 GiB RAM)
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WebSocket Shootout
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Testing
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Testing Cable
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Extensibility
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• Server Abstraction
Extended Cable
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• Server Abstraction
• Protocol Extensions (e.g.
serialization, authentication,
presence feature)
Extended Cable
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Other
• Fallbacks / Transport
• Rails-ness
• Consistency
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Consistency
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Consistency?
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How to Make it
Better?
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Testing Cable
, 2016
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Testing Cable
class ServiceTest < ActionCable::TestCase
def test_assert_transmited_message
Service.broadcast 'messages', 'hi!'
assert_broadcast_on('messages', text: 'hi!')
end
def test_assert_broadcast_on_again
assert_broadcast_on('messages','h!') do
Service.broadcast 'messages', text: 'h!'
end
end
end
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Testing Cable
class ChannelTest < ActionCable::Channel::TestCase
def test_subscribed_with_room_number
subscribe room_number: 1
assert subscription.confirmed?
assert "chat_1", streams.last
end
def test_perform_speak
subscribe room_number: 1
perform :speak, message: "Hello"
assert_equal "Hello",
transmissions.last["message"]["text"]
end
end
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PRs Cable
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PRs Cable
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AnyCable
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Server
Channels
Streams
Client (Protocol)
Action Cable AnyCable
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Server
Channels
Streams
Client (Protocol)
Separation of Concerns
Action Cable AnyCable
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AnyCable
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gRPC
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gRPC =
Google RPC
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gRPC =
Universal RPC
Framework
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gRPC =
protobuf + HTTP/2
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AnyCable Servers
anycable-go
erlycable
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Memory Cable
20k connections
MB
0
500
1 000
1 500
2 000
2 500
3 000
3 500
4 000
anycable-go erlycable ActionCable
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Action Cable CPU
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anycable-go CPU
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erlycable CPU
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WebSocket Shootout
Broadcast RTT
0s
1s
2s
3s
4s
5s
6s
7s
8s
9s
10s
Number of connections
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
ActionCable anycable-go erlycable
Running on AWS EC2 c3.4xlarge (16 vCPU, 30 GiB RAM)
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Compatibility
Feature Status
Connection Identifiers +
Connection Request (cookies, params) +
Disconnect Handling +
Subscribe to channels +
Parameterized subscriptions +
Unsubscribe from channels +
Subscription Instance Variables -
Performing Channel Actions +
Streaming +
Custom stream callbacks -
Broadcasting +
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Action Cable Channel
class ChatChannel < ApplicationCable::Channel
def subscribed
stream_from "chat_#{chat_id}" do |msg|
if msg['sent_at'].present?
delay = Time.now.to_f - msg['sent_at']
logger.info "Message delay #{delay}s"
end
transmit msg
end
end
end
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PRs Cable
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WebSocket Shootout
Broadcast RTT
0s
1s
2s
3s
4s
5s
6s
7s
8s
9s
10s
Number of connections
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
ActionCable Patch 1
Running on AWS EC2 c3.4xlarge (16 vCPU, 30 GiB RAM)
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Where To
anycable.io
github.com/anycable
twitter.com/any_cable
gitter.im/anycable
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PRs Cable
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Server Adapter
# config/application.rb
# specify server adapter
config.action_cable.server = :plezi
# or
config.action_cable.server = :any_cable
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plezi.io
github.com/boazsegev/iodine
Plezi
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LiteCable
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• Rails-free Action Cable
• No deps (even ActiveSupport)
• Compatible with AnyCable
LiteCable
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LiteCable
module Chat
# ...
class Channel < LiteCable::Channel::Base
identifier :chat
def subscribed
stream_from "chat_#{chat_id}"
end
end
end
run Rack::Builder.new do
map '/cable' do
use LiteCable::Server::Middleware,
connection_class: Chat::Connection
run proc { |_| [200, {}, ['']] }
end
end
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LiteCable
github.com/palkan/litecable
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• Testing Support PRs
• AnyCable for Performance
• LiteCable for non-Rails
• ACLI for development/testing
What We Have
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• Action Cable CLI
• mRuby
• Download'n'Run
ACLI
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ACLI
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What's Next?
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History Stream
class ChatChannel < ApplicationCable::Channel
def subscribed
stream_from "chat_#{id}",
history: { time: 5.minutes }
end
end
class ChatChannel < ApplicationCable::Channel
def subscribed
stream_from "chat_#{chat_id}",
history: { size: 100 }
end
end
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Presence
class ChatChannel < ApplicationCable::Channel
def subscribed
stream_from "chat_#{id}",
presence: { user_id: user_id }
end
end
// js client
cable.subscriptions.create(
{ channel: 'chat', id: roomId },
{
presenceUpdated: function(diff) { … }
}
)
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cult of martians.com
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Let's make Action Cable
suck less!
Vladimir Dementyev
evilmartians.com
@palkan
@palkan_tula