Welcome to the Reactive Revolution:RSocket and Spring Cloud Gateway by Spencer Gibb at SpringOne Tour 2019

1. Welcome to the Reactive Revolution:
RSocket & Spring Cloud Gateway
Spencer Gibb, Co-founder and Co-lead of Spring Cloud
@spencerbgibb
Contributions from
Ben Hale @nebhale and Rossen Stoyanchev @rstoya05

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3. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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Reactive Programming
• Reactive programming is the next frontier in Java for high-efficiency
applications
• Fundamentally non-blocking and often paired with asynchronous
behaviors
• Reactive has no opinion on async and many flows are totally
synchronous
• Key differentiator from "async" is Reactive (pull-push) back pressure
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4. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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Roadblocks
• But there are still some barriers to using Reactive everywhere*
• Data Access
• MongoDB, Apache Cassandra, and Redis
• Relational database access is in its infancy (r2dbc.io)
• Cross-process back pressure (networking)
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http://rsocket.io
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RSocket
• RSocket is a bi-directional, multiplexed, message-based, binary protocol
based on Reactive Streams back pressure
• It provides out of the box support for four common interaction models
• Request-Response (1 to 1)
• Fire-and-Forget (1 to 0)
• Request-Stream (1 to many)
• Request-Channel (many to many)
Transport Agnostic: TCP, WebSocket, Aeron UDP ...
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Message Driven Binary Protocol
• Requester-Responder interaction is broken down into frames that
encapsulate messages
• The framing is binary (not human readable like JSON or XML)
• Massive efficiencies for machine-to-machine communication
• Downsides only manifest rarely and can be mitigated with tooling
• Payloads are bags of bytes
• Can be JSON or XML (it's all just 1's and 0's)
Spring Framework 5.2 Messaging Support
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Multiplexed
• Connections that are only used for a single request are massively
inefficient (HTTP 1.0)
• Pipelining (ordering requests and responses sequentially) is a naive
attempt solving the issue, but results in head-of-line blocking (HTTP 1.1)
• Multiplexing solves the issue by annotating each message on the
connection with a stream id that partitions the connection into multiple
"logical streams"
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Bi-Directional
• Many protocols (notably not TCP) have a distinction between the client
and server for the lifetime of a connection
• This division means that one side of the connection must initiate all
requests, and the other side must initiate all responses
• Even more flexible protocols like HTTP/2 do not fully drop the distinction
• Servers cannot start an unrequested stream of data to the client
• Once a client initiates a connection to a server, both parties can be
requesters or responders to a logical stream
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Metadata and Data in Frames
• Each Frame has an optional metadata payload
• The metadata payload has a MIME-Type but is otherwise unstructured
• Very flexible
• Can be used to carry metadata about the data payload
• Can be used to carry metadata in order to decode the payload
• More specific announcement and routing metadata extensions
forthcoming
• Generally means that payloads can be heterogenous and each message
decoded uniquely
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Reactive Streams Back Pressure
• Network protocols generally send a single request, and receive an
arbitrarily large response in return
• There is nothing to stop the responder (or even the requestor) from
sending an arbitrarily large amount of data and overwhelming the receiver
• In cases where TCP back pressure throttles the responder, queues fill
with large amounts of un-transferred data
• Reactive Streams (pull-push) back pressure ensures that data is only
materialized and transferred when receiver is ready to process it
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Spring Cloud Gateway RSocket

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An RSocket Proxy
● Implemented with RSocket Java
● RSocket Java is built with Project Reactor
● Spring Boot
● Provides routing functionality
Registration and Discovery
● Connection level metadata
○ Who am I? Name and Id
● Request level metadata
○ Where do I want to go? Name and Destination*
•
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14. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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Socket Acceptor
package io.rsocket;
public interface SocketAcceptor {
Mono<RSocket> accept(ConnectionSetupPayload setup,
RSocket sendingSocket);
}

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On Connect
15
Gateway
RSocket
Client
RSocket
Client
Socket
Acceptor
Filter
Chain
Registry
Gateway
RSocket
Sending
RSocket
Routes
Step 1: Connect
● Metadata:
name=serviceA
id=serviceA:1

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On Connect
16
Gateway
RSocket
Client
RSocket
Client
Socket
Acceptor
Filter
Chain
Registry
Gateway
RSocket
Sending
RSocket
Routes
Step 2: Filter Chain
● Exchange created with metadata
● @Bean MySocketAcceptorFilter
● Empty result short circuits filter
chain.

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On Connect
17
Gateway
RSocket
Client
RSocket
Client
Socket
Acceptor
Filter
Chain
Registry
Gateway
RSocket
Sending
RSocket
RoutesStep 3: Sending RSocket added to
Registry
● “Socket used to send
requests to the peer”

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On Connect
18
Gateway
RSocket
Client
RSocket
Client
Socket
Acceptor
Filter
Chain
Registry
Gateway
RSocket
Sending
RSocket
RoutesStep 4: A Route is created
● With a predicate that
matches on name metadata

19. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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On Connect
19
Gateway
RSocket
Client
RSocket
Client
Socket
Acceptor
Filter
Chain
Registry
Gateway
RSocket
Sending
RSocket
Routes
Step 5: GatewayRSocket Created
● Decorated with Micrometer
for socket level metrics.
● “Socket to accept requests
from the peer.”

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Let’s Connect
● Gateway clients never receive connections
○ Only make outbound connections
● Socket Acceptor Filter Chain
○ Allows custom security
2
0

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On Request
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Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 1: Request
● ex: Request Response
● Metadata:
name=serviceA
destination*=echo

22. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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On Request
2
2
Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 2: Find a Route
● Exchange created using
request type & metadata
● Predicates tested against
exchange.
● Exchange modeled after
Webflux, has attributes
map

23. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
On Request
2
3
Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 3: Filter Chain
● Route added as exchange
attribute
● Empty result short circuts
the request

24. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
On Request
2
4
Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 4: Find Registered RSocket
● Matches request metadata
with registered metadata
● If no RSocket is found a
PendingRSocket is created

25. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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On Request
2
5
Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 5: Load Balancing
● If multiple RSockets
found, apply load
balancing algorithm.
● Plans for unfair and
round robin

26. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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On Request
2
6
Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 5: Proxy Request
● Request level metrics
are recorded with
Micrometer
● Remember: Full Duplex

27. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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Demo

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Demo setup without Gateway
2
8
Ping
Client 2
Ping
Client 1
Pong
Server

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Demo setup
2
9
Gateway
Ping
Client 2
Ping
Client 1
Pong
Server?

30. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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Clustering (Enhancement)
● To scale, Gateway RSocket needs state
● Plan to use implementation of SWIM:
Scalable Weakly-consistent Infection-style
Process Group Membership Protocol
○ Same algorithm used in Consul and others
● Clients only need seed members of cluster
● Registries of cluster members replicated locally
• http://www.cs.cornell.edu/projects/Quicksilver/public_pdfs/SWIM.pdf
3
0

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On Request: Clustered
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Gateway
RSocket
Client
RSocket
Client
Gateway RSocket
Predicates
Registry
RSocket
Routes
Filter
Chain
Step 4: Find Registered RSocket
● Matches request metadata
with registered metadata
● This could be another
Gateway in the cluster!

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Demo

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Demo setup
33
Gateway
1
Ping
Client 1
Pong
Server
Gateway
2
Masquerade
● Gateway 2 will identify itself
as a pong server

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Things you don’t need...
● Ingress permissions (except Gateway)
● Separate Service Discovery
● Message Broker
● Circuit Breaker
● Client-side load balancer
● Sidecar
● Startup ordering problems
● Special cases for warmup
•
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35. Unless otherwise indicated, these slides are © 2013-2018 Pivotal Software, Inc. and licensed under a Creative Commons
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Additional Benefits
● via RSocket
○ persistent, multiplexed connections
○ multiple transports (TCP, Websockets, Http/2, etc…)
○ polyglot
■ only need standardized connection and request
metadata
● Metrics via Micrometer
•
3
5

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Roadmap
● Clustering
● Tracing integration
● Routing optimization
● Failure tolerance improvements
Release Information
● Builds on Spring Framework 5.2 & Spring Boot 2.2
● Part of Spring Cloud Hoxton
● Targets Q3 2019
○ milestones and release candidates prior
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6

37. > Stay Connected.
http://rsocket.io
https://github.com/spring-cloud/spring-cloud-gateway/tree/rsocket
https://github.com/spencergibb/spring-cloud-gateway-rsocket-sample
@spencerbgibb
#springone@s1p