I Can’t Believe It’s Not A Queue: Using Kafka with Rails - RailsConf 2016

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Happy Star Wars Day

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Terence Lee @hone02

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#rubykaraoke

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#rubykaroke, Thurs 7pm @ Offkey

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I Can't Believe It's Not a Queue Using Kafka with Rails

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Agenda ● What is Kafka? ● Kafka + Ruby ● Use Case: Metrics ● Other Patterns

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What is Kafka?

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Kafka is a distributed, partitioned, replicated commit log service. It provides the functionality of a messaging system, but with a unique design.

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Distributed Publish Subscribe Messaging

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Fast Scalable Durable

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"hundreds of thousands to millions of messages a second on a small cluster" Tom Crayford Heroku Kafka

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Producers & Consumers

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Messages Byte Arrays -> String JSON Any format

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Feed of Messages in Topics

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Each Topic Partition is a log of ordered immutable messages, append-only

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Offets

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Keyed Messages will be consumed by the same consumer

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Consumer Groups allow scaling per topic and ensure each message gets at least once

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Consumer Groups

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Kafka + Ruby

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jruby-kafka

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kafka-ruby

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Simple Producer require "kafka" kafka = Kafka.new(seed_brokers: ["kafka1:9092", "kafka2:9092"]) producer = kafka.producer

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Send a message require "kafka" kafka = Kafka.new(seed_brokers: ["kafka1:9092", "kafka2:9092"]) producer = kafka.producer producer.produce("hello1", topic: "test-messages")

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Keyed Message require "kafka" kafka = Kafka.new(seed_brokers: ["kafka1:9092", "kafka2:9092"]) producer = kafka.producer producer.produce("hello1", topic: "test-messages") producer.produce("hello2", key: "x", topic: "test-messages")

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Message to a Partition require "kafka" kafka = Kafka.new(seed_brokers: ["kafka1:9092", "kafka2:9092"]) producer = kafka.producer producer.produce("hello1", topic: "test-messages") producer.produce("hello2", key: "x", topic: "test-messages") producer.produce("hello3", topic: "test-messages", partition: 1)

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Deliver Messages require "kafka" kafka = Kafka.new(seed_brokers: ["kafka1:9092", "kafka2:9092"]) producer = kafka.producer producer.produce("hello1", topic: "test-messages") producer.produce("hello2", key: "x", topic: "test-messages") producer.produce("hello3", topic: "test-messages", partition: 1) producer.deliver_messages

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Async Producer # `async_producer` will create a new asynchronous producer. producer = kafka.async_producer( # Trigger a delivery once 100 messages have been buffered. delivery_threshold: 100, # Trigger a delivery every second. delivery_interval: 1, )

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Serialization event = { "name" => "pageview", "url" => "https://example.com/posts/123", # ... } data = JSON.dump(event) producer.produce(data, topic: "events")

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Rails Producer # config/initializers/kafka_producer.rb require "kafka" # Configure the Kafka client with the broker hosts and the Rails # logger. $kafka = Kafka.new( seed_brokers: ["kafka1:9092", "kafka2:9092"], logger: Rails.logger, )

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Rails Producer # ... # Set up an asynchronous producer that delivers its buffered messages # every ten seconds: $kafka_producer = $kafka.async_producer( delivery_interval: 10, ) # Make sure to shut down the producer when exiting. at_exit { $kafka_producer.shutdown }

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Rails Producer class OrdersController def create @order = Order.create!(params[:order]) event = { order_id: @order.id, amount: @order.amount, timestamp: Time.now, } $kafka_producer.produce(event.to_json, topic: "order_events") end end

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Consumer API Experimental

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Consumer Groups consumer = kafka.consumer(group_id: "my-consumer") consumer.subscribe("greetings") consumer.each_message do |message| puts message.topic, message.partition puts message.offset, message.key, message.value end

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SSL Kafka.new( seed_brokers: ["kafka1:9092", "kafka2:9092"], ssl_client_cert: ENV['KAFKA_CLIENT_CERT'], ssl_client_cert_key: ENV['KAFKA_CLIENT_CERT_KEY'], ssl_ca_cert: ENV['KAFKA_TRUSTED_CERT'] )

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Use Case: Metrics

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Build metrics based on web traffic

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Architecture

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Architecture

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Heroku Router Logs $ heroku logs -a issuetriage -p router 2016-05-04T04:57:12.222253+00:00 heroku[router]: at=info method=GET path="/haiwen/seafile" host=issuetriage.herokuapp.com request_id=cf59a503-3159-4d7c-8287-3ba52d7c44df fwd=" 144.76.27.118" dyno=web.2 connect=0ms service=166ms status=200 bytes=36360

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Log Drain over HTTPS $ heroku drains:add \ https://user:pass@logdrain.herokuapp.com/logs \ -a issuetriage

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POST Request Body 83 <40>1 2012-11-30T06:45:29+00:00 host app web.3 - State changed from starting to up 119 <40>1 2012-11-30T06:45:26+00:00 host app web.3 - Starting process with command `bundle exec rackup config.ru -p 24405` does NOT conform to RFC5424. It leaves out STRUCTURED-DATA but does not replace it with a NILVALUE.

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Architecture

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Log Drain App (Producer) post "/process" do process_messages(body) status 202 "Accepted" end

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Log Drain App (Producer) $kafka_pools = { producer: ConnectionPool.new(size: 5, timeout: 5) { Kafka.new (...).async_producer }, }

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Log Drain App (Producer) def process_messages(body_text) messages = [] stream = Syslog::Stream.new( Syslog::Stream:: OctetCountingFraming.new(StringIO.new(body_text)), parser: Syslog::Parser.new(allow_missing_structured_data: true) ) messages = stream.messages.to_a

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Log Drain App (Producer) $kafka_pools[:producer].with do |producer| messages.each do |message| producer.produce(message.to_h.to_json, topic: message. procid) if message.procid == "router" end end end

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Architecture

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Heroku Kafka

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Create a Heroku Kafka Cluster $ heroku addons:create heroku-kafka:beta-dev -a kafka-demo Creating kafka-reticulated-61055... done, (free) Adding kafka-reticulated-61055 to kafka-demo... done The cluster should be available in 15-45 minutes. Run `heroku kafka:wait` to wait until the cluster is ready. ! WARNING: Kafka is in beta. Beta releases have a higher risk of data loss and downtime. ! Use with caution. Use `heroku addons:docs heroku-kafka` to view documentation.

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Connecting to Heroku Kafka Kafka.new( seed_brokers: ENV['KAFKA_URL'] ssl_client_cert: ENV['KAFKA_CLIENT_CERT'], ssl_client_cert_key: ENV['KAFKA_CLIENT_CERT_KEY'], ssl_ca_cert: ENV['KAFKA_TRUSTED_CERT'] )

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Heroku Kafka Plugin $ heroku plugins:install heroku-kafka

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Create a Topic $ heroku kafka:create router

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Cluster Info $ heroku kafka:info === KAFKA_URL Name: kafka-reticulated-61055 Created: 2016-04-19 19:54 UTC Plan: Beta Dev Status: available Version: 0.9.0.0 Topics: 2 topics (see heroku kafka:list) Connections: 0 consumers (0 applications) Messages: 0.37 messages/s Traffic: 28 Bytes/s in / 12.1 KB/s out

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Topic Info $ heroku kafka:topic router === KAFKA_URL :: router Producers: 0.0 messages/second (0 Bytes/second) total Consumers: 20.8 KB/second total Partitions: 32 partitions Replication Factor: 1 Compaction: Compaction is disabled for router Retention: 24 hours

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Tail Topic $ heroku kafka:tail router router 20 2627 378 {"prival":158,"version":1,"timestamp":"2016- 05-04 08:33:23 +0000","hostname":"ho router 20 2628 371 {"prival":158,"version":1,"timestamp":"2016- 05-04 08:59:00 +0000","hostname":"ho router 20 2629 370 {"prival":158,"version":1,"timestamp":"2016- 05-04 09:22:29 +0000","hostname":"ho

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Architecture

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Metrics Aggregator (Consumer) consumer = Kafka.new(...).consumer(group_id: "metrics") consumer.subscribe("router", default_offset: :latest) redis = Redis.new(url: ENV['REDIS_URL']) metrics = RouteMetrics.new(redis) consumer.each_message do |message| json = JSON.parse(message.value) route = Route.new(json) metrics.insert(route) if route.path end

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Metrics Aggregator (Consumer) def insert(route) path = route.path path_digest = Digest::SHA256.hexdigest(path) @redis.hset "routes", path, path_digest [:service, :connect].each do |metric| value = route.send(metric).to_i key = "#{path_digest}::#{metric}" @redis.hincrby key, "sum", value @redis.hincrby key, "count", 1 @redis.hset key, "average", @redis.hget(key, "sum").to_i / @redis.hget(key, "count").to_f end @redis.hincrby "#{path_digest}::statuses", route.status, 1 end

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Replay (Consumer) consumer = Kafka.new(...).consumer(group_id: "replay") consumer.subscribe("router", default_offset: :latest) client = HttpClient.httpClient(...) consumer.each_message do |message| json = JSON.parse(message.value) route = Route.new(json) controller.fork.start do client.get(java.net.URI.new("#{ENV ['REPLAY_HOST']}#{route.path}")).then do |response| puts response.get_body.get_text end end end

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Demo Code https://github.com/hone/heroku-replay-ratpack

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Tom Crayford

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Other Patterns

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Messaging ● Low Latency ● High Throughput ● Durability Guarantees

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Activity Tracking ● Real Time feed of User Activity ● One Topic per Activity

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Heroku Metrics

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Heroku API Event Bus

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Kafka's unique design can be used to help Rails apps become fast, scalable, and durable

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Thank You

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Joe Kutner @codefinger

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Community Office Hours Thurs. 4:10pm (Happy Hour) @ Heroku Booth Rails JRuby Heroku